Subtopic 4.1: water Systems
Image from goodmenproject.com
Only a small fraction (2.6% by volume) of the Earth’s water supply is fresh water. Of this, over 80% is in the form of ice caps and glaciers, 0.6% is groundwater and the rest is made up of lakes, soil water, atmospheric water vapour, rivers and biota in decreasing order of storage size.
Irrigation, industrialization and population increase all make demands on the supplies of fresh water. Global warming may disrupt rainfall patterns and water supplies. The hydrological cycle supplies humans with fresh water but we are withdrawing water from underground aquifers and degrading it with wastes at a greater rate than it can be replenished.
In this unit we will look at the increased demand for fresh water, inequity of usage and political consequences, methods of reducing use and increasing supplies.
The SL unit is 2 hours.
Irrigation, industrialization and population increase all make demands on the supplies of fresh water. Global warming may disrupt rainfall patterns and water supplies. The hydrological cycle supplies humans with fresh water but we are withdrawing water from underground aquifers and degrading it with wastes at a greater rate than it can be replenished.
In this unit we will look at the increased demand for fresh water, inequity of usage and political consequences, methods of reducing use and increasing supplies.
The SL unit is 2 hours.
Guiding Questions
- How do water systems support life on Earth, and how do they interact with other systems, such as the
carbon cycle? - How do human activities alter the natural flow of water systems, and what are the potential ecological consequences of these changes?
- In what ways can water systems be managed to ensure long-term sustainability, and what role do different stakeholders (governments, NGOs, communities) play in this process?
Understanding
the hydrological cycle
4.1.1 Movements of water in the hydrosphere are driven by solar radiation and gravity.
- Explain the role of solar radiation in driving the evaporation process.
- Explain how gravity influences the movement of water through rivers and soils
Water constantly moves through different phases in the hydrosphere (the total amount of water on Earth, including oceans, rivers, lakes, and atmosphere). This movement is powered by two primary forces:
Solar Radiation and Evaporation
Condensation and Heat Release
Gravity’s Role in Water Movement
The Hydrological Cycle
- Solar Radiation: Heat from the sun drives processes like evaporation.
- Gravity: Gravity pulls water through soil and rivers, guiding it back to the sea.
Solar Radiation and Evaporation
- Solar energy heats water bodies, causing water molecules to gain enough energy to change from a liquid to a gas, a process known as evaporation.
- Water evaporates from oceans, rivers, lakes, and plant surfaces (transpiration).
- This process is essential for cloud formation, as the water vapor rises into the atmosphere.
Condensation and Heat Release
- As the evaporated water cools in the atmosphere, it condenses into tiny droplets, forming clouds.
- The phase change from vapor to liquid releases latent heat, which is crucial for regulating Earth’s energy balance and drives weather patterns.
Gravity’s Role in Water Movement
- Gravity directs water downward:
- Infiltration: Water seeps into the soil, replenishing groundwater.
- Runoff: Excess water flows over the surface, moving through streams and rivers towards the oceans.
- This flow is part of the hydrological cycle, ensuring that water is continuously circulated and purified.
The Hydrological Cycle
- The continuous movement of water through evaporation, condensation, precipitation, and runoff creates the hydrological cycle.
- This cycle supports life on Earth by distributing water and maintaining ecosystems.
4.1.2 The global hydrological cycle operates as a system with stores and flows
- Identify two major stores in the global hydrological cycle and describe their role in the system.
- Explain how water moves between the atmosphere and oceans in the global hydrological cycle
The global hydrological cycle describes the continuous movement of water within Earth’s atmosphere, surface, and below the ground. It is a closed system, meaning no new water is added to or leaves the system. Instead, it continuously moves between various stores and flows.
Stores in the Hydrological Cycle
Flows in the Hydrological Cycle
The System as a Whole
Stores in the Hydrological Cycle
- Stores are places where water is held for extended periods. In diagrams, stores should be shown as boxes to indicate where water is stored within the cycle.
- Oceans: The largest store, holding about 97% of the Earth's water.
- Ice Caps and Glaciers: Significant stores of freshwater, mostly in polar regions.
- Groundwater: Water stored beneath the Earth’s surface in aquifers.
- Lakes and Rivers: Smaller surface water stores.
- Atmosphere: Holds water in the form of vapor and clouds.
- Soil Moisture: Water stored within the soil.
Flows in the Hydrological Cycle
- Flows represent the movement of water from one store to another.
- Evaporation: Water changes from liquid to vapor, moving from the surface (primarily oceans) to the atmosphere.
- Precipitation: Water returns to the Earth's surface from the atmosphere in the form of rain, snow, sleet, or hail.
- Runoff: Water flows over the ground surface and returns to rivers, lakes, and oceans.
- Infiltration: Water soaks into the ground and replenishes groundwater stores.
- Transpiration: Water is released from plants into the atmosphere.
- Percolation: Water moves deeper into the ground through soil and rocks.
The System as a Whole
- The hydrological cycle is often referred to as a system because it includes:
- Inputs (water entering stores, such as precipitation).
- Outputs (water leaving stores, like evaporation).
- Processes (the flows that move water between stores).
- The cycle is driven by solar energy and gravity, creating a balance between water in the atmosphere, on land, and in oceans.
4.1.3 The main stores in the hydrological cycle are the oceans (96.5%), glaciers and ice caps (1.7%), groundwater (1.7%), surface freshwater (0.02%), atmosphere (0.001%), organisms (0.0001%).
- Outline the amount of freshwater that is part of the Earth’s water storages
- Identify the largest store of water in the hydrological cycle and provide its approximate percentage of Earth's total water
Water budget is a quantitative estimate of the amount of water in stores and flows of the water cycle
The global hydrological cycle has six major water stores, with significant differences in their size:
Relative Proportions of Water Stores
The global hydrological cycle has six major water stores, with significant differences in their size:
- Oceans (~96.5% of all Earth's water)
- The largest store by far, oceans contain almost all of Earth’s water. They are the primary source of evaporation that fuels the water cycle.
- Fun fact: The oceans hold about 1.35 billion cubic kilometers of water!
- Glaciers and Ice Caps (~1.7%)
- Found mostly in Antarctica and Greenland, these stores contain the majority of the Earth’s freshwater.
- Importance: These frozen stores act as long-term reservoirs, releasing water slowly through melting and contributing to sea-level changes.
- Groundwater (~1.7%)
- Groundwater is stored in underground aquifers and provides essential water for human consumption, irrigation, and ecosystems.
- It is a crucial freshwater resource, especially in areas where surface water is scarce.
- Surface Freshwater (~0.02%)
- This includes rivers, lakes, and wetlands, and although small in volume, it is vital for ecosystems and human use.
- Key examples: The Amazon River and the Great Lakes.
- Atmosphere (~0.001%)
- The atmosphere holds water as vapor and clouds, but despite its small proportion, it plays a critical role in transporting water across the planet through precipitation and evaporation.
- Organisms (~0.0001%)
- Living organisms, including plants, animals, and humans, contain a tiny fraction of the world’s water. Water in organisms supports biological processes like photosynthesis and respiration.
Relative Proportions of Water Stores
- The oceans dominate the hydrological cycle, holding the vast majority of Earth's water, while glaciers, ice caps, and groundwater contain nearly all of the freshwater.
- Surface freshwater and atmospheric water may hold only a small fraction of Earth's total water, but they are crucial for life, weather, and climate systems.
4.1.4 Flows in the hydrological cycle include transpiration, sublimation, evaporation, condensation, advection, precipitation, melting, freezing, surface run-off, infiltration, percolation, streamflow and groundwater flow.
- Distinguish between transformation flows and transfer flows within the hydrological cycle.
The hydrological cycle is a dynamic system of flows where water constantly moves between different stores, including oceans, atmosphere, and land. These flows involve both physical and biological processes that are essential for maintaining the balance of water on Earth and supporting life.
Key Flows in the Hydrological Cycle
Below are the main flows that move water between different stores in the cycle:
Transpiration
Each flow in the hydrological cycle has ecological significance:
Key Flows in the Hydrological Cycle
Below are the main flows that move water between different stores in the cycle:
Transpiration
- The process by which plants release water vapor into the atmosphere through tiny pores in their leaves. This flow plays a crucial role in maintaining moisture levels in the atmosphere and contributing to cloud formation.
- This combines evaporation from soil and water surfaces and transpiration from plants. It represents the total loss of water from an area to the atmosphere and is a critical component in the global water balance.
- Importance: Evapotranspiration influences local climate and water availability, particularly in agricultural regions where water management is essential.
- The transformation of ice directly into water vapor without passing through the liquid phase. It occurs in cold regions where snow or ice can turn directly into vapor, often seen in polar areas or on mountaintops.
- The process by which water changes from a liquid to a gas (vapor), driven by heat from the sun. Evaporation primarily happens in oceans, lakes, and rivers, playing a major role in replenishing atmospheric moisture.
- This is the process where water vapor in the atmosphere cools and changes back into liquid droplets, forming clouds. Condensation releases latent heat, which influences weather patterns.
- Refers to the horizontal movement of water vapor, clouds, or frozen water droplets carried by the wind. This process helps distribute moisture around the planet, leading to precipitation in different regions.
- Water falls back to Earth from the atmosphere in the form of rain, snow, sleet, or hail. Precipitation replenishes surface and groundwater stores and supports ecosystems.
- Melting refers to the process where ice or snow turns into liquid water due to heat. Conversely, freezing is the transformation of liquid water into ice when temperatures drop. These processes are especially important in polar regions and glaciers.
- This occurs when precipitation exceeds the infiltration capacity of the ground, causing excess water to flow over the land's surface, eventually reaching rivers, lakes, and oceans.
- Water that falls as precipitation enters the soil through a process known as infiltration. The rate of infiltration depends on soil type, vegetation, and land use.
- After infiltration, water moves deeper into the soil and rocks through percolation. This flow contributes to groundwater storage and recharges aquifers.
- Water that flows in rivers and streams is called streamflow. It represents the movement of surface water across the land, ultimately leading to oceans.
- This refers to the movement of water stored underground in aquifers. Groundwater flow occurs slowly, and it often resurfaces in springs, rivers, or oceans.
Each flow in the hydrological cycle has ecological significance:
- Transpiration, evaporation, and evapotranspiration influence local weather and climate by controlling moisture levels in the atmosphere.
- Runoff, infiltration, and percolation determine how much water is available for plants and animals, while also affecting soil erosion and nutrient distribution.
image from www.eoearth.org
Activity: Create and use a systems diagram showing the transfers and transformations of the hydrological cycle.
Activity: Create a model of a lake using beakers and various amounts of water. Measure the amount of water loss over a period of one week
human impact on the water cycle
4.1.5 Human activities, such as agriculture, deforestation and urbanization, can alter these flows and stores.
- Explain how urbanization affects this flow in the hydrological cycle.
- Identify two ways that deforestation alters the hydrological cycle
- Outline the impact of agricultural practices on groundwater recharge and surface runoff
image from en.wikipedia.org
Human activities have significantly altered the natural flows and stores in the hydrological cycle. Actions such as agriculture, deforestation, and urbanization directly affect the processes of evapotranspiration, infiltration, and runoff, often disrupting the natural balance and leading to environmental consequences like flash floods.
Key Human Activities Affecting Water Flows
Key Human Activities Affecting Water Flows
- Agriculture
- Irrigation and farming practices divert water from natural flows, often increasing surface runoff and reducing groundwater recharge.
- Soil compaction from heavy machinery decreases infiltration rates, leading to more water flowing over the surface.
- Use of fertilizers and pesticides also introduces pollutants into water systems, affecting both surface water and groundwater quality.
https://iopscience.iop.org/article/10.1088/1748-9326/ab05f4
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- Deforestation
- Trees play a crucial role in the water cycle through transpiration, which contributes moisture to the atmosphere.
- When forests are cleared, evapotranspiration is significantly reduced, meaning less water returns to the atmosphere, altering local rainfall patterns.
- The removal of trees also increases surface runoff because forests typically slow water flow and promote infiltration. Without trees, water flows more rapidly across the land, leading to soil erosion and the potential for flash floods.
https://www.researchgate.net/figure/Effect-of-deforestation-on-rainfall-in-the-tropics-a-Much-of-the-rainfall-over-tropical_fig1_230804530
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- Urbanization
- Urban development leads to the creation of impermeable surfaces (e.g., roads, buildings), which block water from infiltrating into the soil.
- This causes an increase in surface runoff, as water has fewer opportunities to infiltrate and percolate into the ground.
- Urban areas often experience flash floods during heavy rainfall events because water cannot penetrate the concrete and asphalt, quickly overwhelming drainage systems.
- Stormwater management infrastructure is needed in urban areas to handle increased runoff and mitigate flood risks.
https://www.researchgate.net/figure/1-Influence-of-the-urbanization-on-the-water-cycle_fig1_343737016
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https://www.researchgate.net/figure/Natural-Catchment-vs-Urban-Catchment-wwwtankonyvtarhu_fig2_332044701
The Impacts of Land Use Changes
When land use changes, such as through deforestation or urbanization, the balance of water flows in the hydrological cycle is disturbed:
When land use changes, such as through deforestation or urbanization, the balance of water flows in the hydrological cycle is disturbed:
- Reduced Evapotranspiration: Fewer plants and trees mean less water is returned to the atmosphere, altering weather patterns and reducing local humidity.
- Increased Runoff: Without vegetation to absorb water, more water flows over the surface. This not only leads to flash floods but also depletes groundwater reserves, as less water infiltrates the soil.
- Flash Floods: Rapid surface runoff causes rivers and drainage systems to overflow during heavy rains, resulting in sudden and destructive floods.
Activity: Research how urbanization in a major city has affected water runoff and local water management systems
4.1.6 The steady state of any water body can be demonstrated through flow diagrams of inputs and outputs.
- Outline the importance of maintaining a steady state in an aquifer
- Explain how flow diagrams can be used to determine sustainable rates of water extraction from an aquifer.
Water bodies, such as lakes, rivers, and aquifers, maintain a steady state when the amount of water entering (inputs) is equal to the amount leaving (outputs). This balance is critical for maintaining sustainable water resources and ensuring that human activities, such as water extraction, do not deplete these systems beyond their capacity to replenish.
Inputs and Outputs in Water Bodies
Water bodies receive water from various inputs and lose water through several outputs. Understanding these flows allows us to manage water resources sustainably.
Flow Diagrams to Represent Water Balance
A flow diagram is a useful tool to visually represent the balance of water inputs and outputs in a system. It helps illustrate whether a water body is in a steady state or if there are imbalances that could lead to issues like water shortages or depletion of the resource. In a flow diagram:
An example of such a diagram could include:
This helps visualize the water balance and determine if water is being used sustainably.
Calculating Sustainable Harvesting Rates
Flow diagrams are not just illustrative; they can be used to calculate sustainable rates of harvesting from lakes or aquifers. Sustainable harvesting means extracting water at a rate that allows the system to replenish without long-term depletion.
Example Calculation
Consider an aquifer that receives 100 million cubic meters of water per year (inputs) from precipitation and groundwater recharge. The system loses 50 million cubic meters to natural outflow and 20 million cubic meters to evaporation (outputs). The remaining 30 million cubic meters is available for sustainable extraction. If more than 30 million cubic meters is extracted annually, the aquifer's water levels will drop, making the rate unsustainable.
Case Study: Over-extraction of Aquifers
In many parts of the world, groundwater is being extracted faster than it can be replenished, leading to aquifer depletion. For example:
Inputs and Outputs in Water Bodies
Water bodies receive water from various inputs and lose water through several outputs. Understanding these flows allows us to manage water resources sustainably.
- Inputs:
- Precipitation: Rainfall or snowfall directly onto the water body.
- Inflow: Water from rivers, streams, and runoff flowing into the lake or aquifer.
- Groundwater Recharge: Water seeping into the aquifer from surrounding soil or surface water.
- Artificial Inputs: Water diverted from other sources, such as reservoirs or irrigation systems.
- Outputs:
- Evaporation: Water turning into vapor and leaving the system.
- Outflow: Water leaving through rivers or streams connected to the water body.
- Groundwater Discharge: Water seeping out of an aquifer into surrounding areas.
- Human Extraction: Water removed for agricultural, industrial, or domestic use.
Flow Diagrams to Represent Water Balance
A flow diagram is a useful tool to visually represent the balance of water inputs and outputs in a system. It helps illustrate whether a water body is in a steady state or if there are imbalances that could lead to issues like water shortages or depletion of the resource. In a flow diagram:
- Boxes represent the water body (store), such as a lake or aquifer.
- Arrows represent the flows of water in and out of the system. Inputs are shown as arrows entering the box, and outputs as arrows leaving the box.
An example of such a diagram could include:
- Arrows representing precipitation and river inflow going into the lake.
- Arrows for evaporation, groundwater discharge, and outflow indicating water leaving the lake.
This helps visualize the water balance and determine if water is being used sustainably.
Calculating Sustainable Harvesting Rates
Flow diagrams are not just illustrative; they can be used to calculate sustainable rates of harvesting from lakes or aquifers. Sustainable harvesting means extracting water at a rate that allows the system to replenish without long-term depletion.
- Sustainable Yield: The amount of water that can be extracted while maintaining a steady state in the water body.
- This requires balancing water inputs (precipitation, inflow, recharge) with outputs (extraction, evaporation, discharge).
- If inputs exceed outputs, the water body may accumulate water, but if outputs exceed inputs, the water body will shrink, potentially leading to depletion.
Example Calculation
Consider an aquifer that receives 100 million cubic meters of water per year (inputs) from precipitation and groundwater recharge. The system loses 50 million cubic meters to natural outflow and 20 million cubic meters to evaporation (outputs). The remaining 30 million cubic meters is available for sustainable extraction. If more than 30 million cubic meters is extracted annually, the aquifer's water levels will drop, making the rate unsustainable.
Case Study: Over-extraction of Aquifers
In many parts of the world, groundwater is being extracted faster than it can be replenished, leading to aquifer depletion. For example:
- California’s Central Valley Aquifer: Excessive groundwater extraction for agriculture has caused water levels to drop significantly, creating long-term water shortages and land subsidence.
- The Aral Sea: Over-extraction for irrigation in surrounding areas caused the sea to shrink dramatically, affecting local ecosystems and economies.
hl only
The HL unit is 3 hours
properties of water
4.1.7 Water has unique physical and chemical properties that support and sustain life.
- Define cohesion and explain how it helps plants transport water from roots to leaves
- Outline how water’s solvent properties support life in aquatic ecosystems.
- Explain how water’s high specific heat capacity contributes to temperature regulation in aquatic environments.
Water is essential for all life on Earth, and its unique physical and chemical properties make it an exceptional substance for sustaining life. These properties include polarity, cohesion, adhesion, solvent abilities, transparency, high specific heat capacity, and its variations in density and gas solubility. Together, these properties play crucial roles in biological and ecological systems.
Key Properties of Water
- Polarity
- Water is a polar molecule, meaning it has a slight positive charge on one end (hydrogen atoms) and a slight negative charge on the other (oxygen atom). This polarity allows water molecules to form hydrogen bonds with each other and with other substances.
- Importance for Life: Polarity makes water an excellent medium for dissolving a wide range of substances, making it a critical solvent in biological processes
- Cohesion
- Cohesion refers to the attraction between water molecules due to hydrogen bonding. This property allows water molecules to stick together, forming droplets and allowing water to flow smoothly in rivers, lakes, and even within plants.
- Example: Cohesion supports surface tension, enabling small organisms like insects to walk on water. In plants, cohesion helps water move from roots to leaves through capillary action.
https://old-ib.bioninja.com.au/standard-level/topic-2-molecular-biology/22-water/cohesive-and-adhesive-prope.html
- Adhesion
- Adhesion is the attraction between water molecules and other substances. It allows water to cling to surfaces like plant cell walls or soil particles.
- Example: Adhesion between water molecules and the walls of xylem vessels in plants helps water travel upward, supporting nutrient transport.
- Adhesion is the attraction between water molecules and other substances. It allows water to cling to surfaces like plant cell walls or soil particles.
https://www.albert.io/blog/properties-of-water-ap-biology-crash-course-review/
- Solvent Properties
- Water is known as the "universal solvent" due to its ability to dissolve more substances than any other liquid. Its polarity allows it to interact with various ions and molecules.
- Example: Water dissolves salts, sugars, gases, and many other substances, facilitating chemical reactions in cells, such as digestion and respiration.
https://socratic.org/questions/what-is-the-property-of-water-that-makes-it-the-universal-solvent
- Transparency
- Transparency indicates the clarity of water and is measured using a Secchi disc
- Water is transparent, allowing light to penetrate through it. This is crucial for aquatic ecosystems, as it enables photosynthesis in aquatic plants and algae.
- Water transparency can vary seasonally
- Example: In oceans and lakes, transparency allows sunlight to reach organisms living below the surface, supporting food chains.
- High Specific Heat Capacity
- Water has a high specific heat capacity, meaning it can absorb a lot of heat before its temperature rises significantly. This property allows water to buffer temperature changes in the environment.
- Importance for Life: Water’s ability to regulate temperature helps maintain stable climates and ecosystems. It also protects organisms from rapid temperature fluctuations.
- Differences in Density
- Water exhibits unusual density behavior. It is most dense at 4°C, and as it freezes, it becomes less dense, causing ice to float. This property prevents water bodies from freezing solid, protecting aquatic life in winter.
- Example: Floating ice insulates the water below, keeping it liquid and providing a habitat for fish and other organisms even in freezing conditions.
- Differences in Gas Solubility
- The solubility of gases like oxygen and carbon dioxide in water varies with temperature and pressure. Cooler water can dissolve more gases, which is why cold water holds more dissolved oxygen.
- Importance for Life: Dissolved oxygen is essential for aquatic organisms. As water warms, gas solubility decreases, which can lead to oxygen depletion in ecosystems, affecting aquatic life.
- Example: In deep ocean environments where pressure is high, the water can hold more gases, supporting life at extreme depths. However, in warm shallow waters, lower oxygen levels can lead to fish kills and other ecological disturbances.
oceans as a carbon sink
4.1.8 The oceans act as a carbon sink by absorbing carbon dioxide from the atmosphere and sequestering it.
- Define the term "carbon sink" and explain how oceans function as a carbon sink.
- Identify two processes by which carbon dioxide is sequestered in the oceans.
The oceans play a critical role in the global carbon cycle by acting as a carbon sink, meaning they absorb and store carbon dioxide (CO₂) from the atmosphere. This process has helped moderate the increase in atmospheric CO₂ levels, which have risen due to the burning of fossil fuels. However, there is concern that the oceans could reach a saturation point, limiting their ability to absorb CO₂ in the future.
How Oceans Absorb Carbon Dioxide
The oceans absorb CO₂ through several natural processes:
How Oceans Absorb Carbon Dioxide
The oceans absorb CO₂ through several natural processes:
- Direct Absorption from the Atmosphere:
- Carbon dioxide from the atmosphere dissolves directly into the surface waters of the ocean. Cooler water absorbs more CO₂ than warmer water, making polar oceans particularly effective carbon sinks.
- Biological Sequestration:
- Phytoplankton, microscopic plants in the ocean, absorb CO₂ during photosynthesis, converting it into organic matter. As phytoplankton are consumed by other organisms or die, some of this carbon sinks to the ocean floor, where it can be stored for long periods.
- Physical Carbon Pump:
- Ocean circulation, driven by temperature and salinity differences, helps transport CO₂ from the surface to deeper waters, where it is stored in the deep ocean for centuries.
- Chemical Sequestration:
- CO₂ reacts with seawater to form carbonic acid, which can further dissociate into bicarbonate and carbonate ions. These chemical forms of carbon can remain in the ocean for thousands of years.
Moderating Atmospheric CO₂ Levels
Since the Industrial Revolution, human activities such as burning fossil fuels have dramatically increased atmospheric CO₂ levels. The oceans have absorbed about 25-30% of the excess CO₂, acting as a buffer against climate change by reducing the amount of greenhouse gases in the atmosphere.
This absorption has moderated the rate of global warming by slowing the rise in atmospheric CO₂ levels. Without the ocean’s ability to act as a carbon sink, the impacts of climate change could be more severe.
Potential Risks: Reaching the Saturation Point
There is concern that the oceans may reach a saturation point in their ability to absorb CO₂. Several factors contribute to this:
Consequences of Saturation
If the oceans reach their saturation point, they will no longer be able to absorb CO₂ at the current rate. This could lead to a faster accumulation of CO₂ in the atmosphere, accelerating global warming and intensifying the effects of climate change. The increase in atmospheric CO₂ would lead to more extreme weather events, rising sea levels, and widespread ecological and societal impacts.
Since the Industrial Revolution, human activities such as burning fossil fuels have dramatically increased atmospheric CO₂ levels. The oceans have absorbed about 25-30% of the excess CO₂, acting as a buffer against climate change by reducing the amount of greenhouse gases in the atmosphere.
This absorption has moderated the rate of global warming by slowing the rise in atmospheric CO₂ levels. Without the ocean’s ability to act as a carbon sink, the impacts of climate change could be more severe.
Potential Risks: Reaching the Saturation Point
There is concern that the oceans may reach a saturation point in their ability to absorb CO₂. Several factors contribute to this:
- Warming Oceans:
- As global temperatures rise due to climate change, the oceans are warming. Warm water holds less CO₂ than cold water, reducing the efficiency of the oceans as a carbon sink.
- Ocean Acidification:
- The absorption of CO₂ leads to the formation of carbonic acid, causing ocean acidification. This process lowers the pH of seawater, which can harm marine organisms like coral reefs, shellfish, and plankton that rely on calcium carbonate to form their shells and skeletons. As ocean acidification progresses, it could reduce the ocean's capacity to absorb more CO₂.
- Biological Impacts:
- Disruptions to marine ecosystems, such as the decline of phytoplankton due to ocean warming or acidification, could reduce the biological sequestration of carbon. Phytoplankton play a key role in capturing CO₂ and transferring it to the deep ocean.
- Reduced Mixing of Ocean Layers:
- Climate change may also disrupt ocean circulation patterns, limiting the mixing of surface water and deep water. This could slow down the movement of CO₂ to the deep ocean, where it is stored for long periods.
Consequences of Saturation
If the oceans reach their saturation point, they will no longer be able to absorb CO₂ at the current rate. This could lead to a faster accumulation of CO₂ in the atmosphere, accelerating global warming and intensifying the effects of climate change. The increase in atmospheric CO₂ would lead to more extreme weather events, rising sea levels, and widespread ecological and societal impacts.
4.1.9 Carbon sequestered in oceans over the short term as dissolved carbon dioxide causes ocean acidification; over the longer term, carbon is taken up into living organisms as biomass that accumulates on the seabed.
- Identify two forms of carbon stored in seabed sediments
- Explain how the process of ocean acidification affects marine organisms
- Describe the process by which carbon stored in organic matter on the seabed can eventually become fossil fuels
The oceans play a significant role in the global carbon cycle by absorbing carbon dioxide (CO₂) from the atmosphere. This carbon can be stored in the oceans over both the short term and long term, contributing to processes such as ocean acidification, the accumulation of biomass on the seabed, and eventually the formation of fossil fuels over geological timescales.
Short-Term Carbon Sequestration and Ocean Acidification
In the short term, carbon dioxide is absorbed into the oceans as dissolved CO₂. When CO₂ enters the water, it reacts with seawater to form carbonic acid (H₂CO₃), which dissociates into bicarbonate (HCO₃⁻) and carbonate (CO₃²⁻) ions. This process lowers the pH of the ocean, leading to ocean acidification.
Short-Term Carbon Sequestration and Ocean Acidification
In the short term, carbon dioxide is absorbed into the oceans as dissolved CO₂. When CO₂ enters the water, it reacts with seawater to form carbonic acid (H₂CO₃), which dissociates into bicarbonate (HCO₃⁻) and carbonate (CO₃²⁻) ions. This process lowers the pH of the ocean, leading to ocean acidification.
- Ocean Acidification:
- As CO₂ levels increase in the atmosphere due to human activities (e.g., fossil fuel burning), more CO₂ is absorbed by the oceans.
- The resulting acidification has negative effects on marine life, particularly species that rely on calcium carbonate to form their shells and skeletons, such as corals, mollusks, and some plankton species.
- Acidification can disrupt marine ecosystems, making it harder for organisms to survive, reproduce, and build their shells, affecting entire food webs.
Long-Term Carbon Sequestration: Biomass and Sedimentation
Over the long term, carbon is removed from the surface ocean and stored in the deep ocean through biological processes. Phytoplankton, the primary producers in the ocean, absorb CO₂ during photosynthesis and convert it into organic carbon. This organic carbon is transferred through the marine food web, eventually accumulating in biomass.
- Carbon in Biomass:
- When marine organisms die, their remains (organic carbon) sink to the ocean floor. Some of this biomass is decomposed, but not all of it breaks down completely.
- The accumulation of partially decomposed organic material forms sediments on the seabed, which act as a long-term store of carbon.
- Seabed Sediments:
- These sediments consist of both inorganic carbonates (from shells and skeletons of marine organisms) and organic carbon compounds (from decomposing organisms).
- Over millions of years, these sediments can become compacted and subjected to heat and pressure, forming fossil fuels like oil, coal, and natural gas.
The Role of Sedimentation in Carbon Sequestration
Sedimentation is a slow but essential process for removing carbon from the active carbon cycle and storing it in long-term reservoirs on the ocean floor. This process locks away carbon for millions of years, helping to regulate atmospheric CO₂ levels over geological timescales.
- Formation of Fossil Fuels:
- Organic matter that is buried in ocean sediments can, under the right conditions, become fossil fuels after millions of years. This process is known as carbonification.
- The extraction and burning of fossil fuels release this stored carbon back into the atmosphere, contributing to modern-day CO₂ emissions and climate change.
The Carbonate Buffering System
- The oceans act as a natural buffer against rapid changes in atmospheric CO₂ levels by dissolving excess CO₂ and converting it into bicarbonate and carbonate ions.
- This buffering capacity helps stabilize the global climate but comes with the drawback of ocean acidification.
Impact of Ocean Acidification and Fossil Fuel Formation
While the ocean's ability to store carbon is essential for moderating atmospheric CO₂, there are long-term consequences:
- Ocean Acidification continues to threaten marine biodiversity, particularly organisms that rely on calcium carbonate.
- Sedimentation and Fossil Fuel Formation represent slow but vital processes in the carbon cycle, balancing carbon over millennia. However, human activities have rapidly accelerated the release of stored carbon by burning fossil fuels, contributing to climate change.
water stratification
4.1.10 The temperature of water varies with depth, with cold water below and warmer water above. Differences in density restrict mixing between the layers, leading to persistent stratification.
- Define thermal stratification in a body of water and explain why it occurs.
- Explain how stratification in lakes affects the distribution of oxygen and nutrients during the summer and winter seasons
Water temperature varies with depth, creating distinct layers in bodies of water. This thermal stratification occurs because warmer water, which is less dense, stays near the surface, while colder, denser water settles below. This layering restricts the mixing of water between the layers and plays a significant role in the survival of freshwater ecosystems, particularly in cold climates.
Thermal Stratification and Density
Thermal Stratification and Density
- Stratification occurs in lakes, ponds, and oceans, where water forms distinct temperature layers.
- The epilimnion is the upper, warmer layer.
- The hypolimnion is the deeper, colder layer.
- These layers are separated by the thermocline, a zone where the temperature drops rapidly with increasing depth.
- Density and Temperature Relationship:
- Water is most dense at 4°C. As water cools below this temperature, it becomes less dense and begins to float above denser, slightly warmer water.
- This unique property means that water bodies freeze from the surface downwards, creating an insulating layer of ice that protects aquatic life during winter.
Why Water Density Matters
Seasonal Changes and Turnover
- Preventing Complete Freezing:
- As temperatures drop, the surface water of lakes and ponds cools to 0°C and freezes, but the water beneath the ice remains liquid and typically around 4°C. This phenomenon ensures that freshwater ecosystems can survive through the winter under the protective layer of ice.
- Example: Fish and other aquatic organisms are able to live in the liquid water below the ice layer, even when temperatures on the surface are freezing.
- Stratification and Limited Mixing:
- Density differences between the warm and cold layers prevent them from mixing easily. This persistent stratification means that oxygen, nutrients, and temperature do not readily transfer between the layers.
- Impacts: In the summer, the surface layer (epilimnion) may be oxygen-rich but nutrient-poor, while the deeper layer (hypolimnion) may be nutrient-rich but oxygen-poor. In autumn and spring, as surface water cools or warms, seasonal turnover can mix the layers, redistributing oxygen and nutrients throughout the water body.
Seasonal Changes and Turnover
- In Winter:
- The top layer of the water body freezes while the bottom layers stay liquid, maintaining an environment where aquatic life can survive.
- The ice layer acts as an insulator, preventing deeper water from freezing.
- In Spring and Autumn:
- As temperatures change, the surface water cools or warms, eventually matching the temperature of the deeper layers.
- This leads to mixing or turnover, which redistributes oxygen and nutrients throughout the water column, supporting the entire ecosystem.
https://www.lakehomes.com/info/lifestyles/the-science-behind-lake-stratification
Ecological Importance of Stratification and Ice Formation
- Protection of Freshwater Ecosystems:
- The ice layer on top of lakes and ponds provides an insulating barrier that helps preserve the water temperature below, allowing organisms such as fish, amphibians, and invertebrates to survive even in cold winters.
- Example: In the Arctic, lakes can be covered in ice for months, but the aquatic ecosystem below continues to function.
- Nutrient and Oxygen Distribution:
- Thermal stratification plays a key role in the distribution of oxygen and nutrients, which can impact productivity and biodiversity within the ecosystem.
- During summer, surface waters may become oxygen-depleted due to the stratification, and in autumn, the turnover allows for the redistribution of oxygen and nutrients, reoxygenating the deeper layers.
- Impacts of Climate Change:
- Rising global temperatures may disrupt the normal patterns of stratification and seasonal turnover, affecting oxygen levels, nutrient cycles, and the overall health of aquatic ecosystems.
4.1.11 Stratification occurs in deeper lakes, coastal areas, enclosed seas and open ocean, with a thermocline forming a transition layer between the warmer mixed layer at the surface and the cooler water below.
- Explain the role of the thermocline in separating water layers.
- Identify the differences in dissolved oxygen levels between the surface water and deep water in stratified systems.
- Explain how stratification in the ocean affects the availability of nutrients for surface-dwelling organisms.
Stratification refers to the formation of distinct layers in a body of water, primarily due to temperature differences between the surface and deeper water. This process occurs in deeper lakes, coastal areas, enclosed seas, and the open ocean, where a sharp temperature gradient, called the thermocline, separates the warm surface water from the cold, deeper layers. This separation restricts mixing between the layers, which has significant ecological and environmental implications.
https://www.coexploration.org/bermuda/html/thermocline_graph.html
How Stratification Works
Locations Where Stratification Occurs
Stratification occurs in various aquatic environments:
- Warmer Surface Layer: This is the epilimnion, the topmost layer that is heated by the sun and mixed by wind and waves. This layer is typically warmer, lighter, and less dense.
- Colder Deep Layer: The hypolimnion is the cooler, denser water found below the thermocline. This layer is typically more stable, with minimal mixing.
- Thermocline: The thermocline is the transition layer between the warm surface water and the cold deep water. The temperature in this layer drops rapidly with increasing depth, creating a distinct boundary that prevents the easy mixing of water from the layers above and below.
Locations Where Stratification Occurs
Stratification occurs in various aquatic environments:
- Deeper Lakes: Stratification is common in temperate lakes, especially during summer, when the surface water heats up, creating a stable thermocline.
- Coastal Areas: In shallow coastal waters, stratification can occur seasonally due to changes in surface temperatures and freshwater input from rivers.
- Enclosed Seas: Seas with limited water exchange (e.g., the Mediterranean) experience strong stratification due to their semi-enclosed nature.
- Open Ocean: In the open ocean, stratification is common in tropical and temperate regions, where surface warming leads to distinct layers.
Differences in Dissolved Oxygen and Nutrients Between Layers
Stratification also affects the distribution of dissolved oxygen and mineral nutrients in water bodies.
Impact of Stratification on Ecosystems
Stratification also affects the distribution of dissolved oxygen and mineral nutrients in water bodies.
- Dissolved Oxygen:
- Surface Water: The warm, mixed surface layer is usually oxygen-rich due to contact with the atmosphere and the activity of photosynthetic organisms like phytoplankton.
- Deep Water: The colder deep water typically has lower oxygen levels because it is isolated from the surface and lacks light for photosynthesis. In some cases, especially in enclosed seas, the deep layer can become hypoxic (low in oxygen) or even anoxic (completely lacking oxygen).
- Mineral Nutrients:
- Surface Water: While rich in oxygen, the surface layer tends to be nutrient-poor because nutrients are consumed by organisms and are not easily replenished due to the lack of mixing with deeper layers.
- Deep Water: The deeper, colder layer is often nutrient-rich, as nutrients from decomposing organic matter accumulate over time. However, these nutrients are largely inaccessible to surface organisms unless upwelling or mixing events bring them to the surface.
Impact of Stratification on Ecosystems
- Productivity: Stratification can limit the availability of nutrients in the surface waters, affecting the productivity of marine and freshwater ecosystems. Phytoplankton, which rely on nutrients for growth, may experience nutrient limitations in stratified systems, reducing overall biological productivity.
- Oxygen Depletion: In the deep layers, especially in enclosed seas or lakes, oxygen can become depleted over time due to the lack of mixing and the consumption of oxygen by decomposing organic matter. This can lead to the formation of dead zones, where low oxygen levels make it difficult for most marine life to survive.
4.1.12 Global warming and salinity changes have increased the intensity of ocean stratification.
- Explain how global warming affects the intensity of stratification
- Identify one way that melting ice caps in Antarctica are contributing to changes in ocean stratification.
Global warming and changes in salinity are intensifying the stratification of the ocean, particularly in the upper layers. Stratification refers to the formation of distinct layers in the ocean based on temperature and salinity, which affects the mixing of water and the distribution of heat, nutrients, and gases. These changes are most pronounced in the upper 200 meters of water, where warming and freshwater input are significantly altering the ocean's natural balance.
Global Warming and Increased Stratification
Salinity Changes and Stratification
Consequences of Increased Stratification
Global Warming and Increased Stratification
- Warming of Surface Waters:
- Global warming has led to an increase in the temperature of the Earth's oceans, particularly in the upper layers.
- Warmer surface waters are less dense than the colder, deeper waters, intensifying the separation between the surface and deep layers (i.e., stronger stratification).
- This increased stratification limits vertical mixing, preventing the exchange of nutrients, oxygen, and heat between surface and deep waters.
- Effects of Temperature on Stratification:
- The temperature difference between warm surface water and cooler deep water is most pronounced in the upper 200 meters, where sunlight penetrates and heats the surface.
- Surface water warms faster than deeper water, reinforcing the thermocline (the boundary separating warm and cold water layers).
- Global impact: Warmer surface waters are observed across the globe, leading to stronger stratification in tropical, temperate, and polar regions.
Salinity Changes and Stratification
- Melting Ice Caps and Freshwater Input:
- The melting of ice caps and glaciers, particularly in Antarctica, is releasing large amounts of freshwater into the oceans, decreasing salinity in polar regions.
- Freshwater is less dense than saltwater, and its input into the oceans increases stratification by creating a buoyant layer of lower-salinity water that floats on top of the denser, saltier water below.
- Antarctica: The reduction in salinity due to ice melt is most pronounced around Antarctica, where the influx of freshwater from melting ice caps disrupts ocean circulation patterns, contributing to changes in stratification.
- Salinity and Density:
- Salinity plays a key role in determining the density of seawater. The lower the salinity, the less dense the water becomes, and this enhances stratification when freshwater from melting ice or increased precipitation is added to the surface.
- In regions where the salinity is reduced, such as around the poles, the stratification becomes stronger, further limiting the mixing of surface and deep waters.
Consequences of Increased Stratification
- Reduced Vertical Mixing:
- Increased stratification reduces the vertical mixing of water, which has several ecological and physical impacts:
- Nutrient Depletion: Surface waters become depleted of nutrients as the deep, nutrient-rich waters are not able to mix with the surface. This leads to reduced productivity, particularly for phytoplankton, which form the base of marine food chains.
- Oxygen Reduction: Stratification limits the transport of oxygen to deeper waters, potentially leading to hypoxia (low oxygen) in the deep layers, which can create dead zones where marine life struggles to survive.
- Increased stratification reduces the vertical mixing of water, which has several ecological and physical impacts:
- Impact on Marine Ecosystems:
- The lack of nutrient mixing and reduced oxygen levels can negatively impact marine ecosystems, particularly in regions where marine productivity depends on nutrient upwelling from deeper layers.
- Fish populations, marine mammals, and other marine species are directly affected by changes in water temperature, oxygen availability, and food resources.
- Global Impacts:
- Stratification changes are having a global effect due to the widespread warming of the oceans and the increasing contribution of freshwater from melting ice caps.
- Polar regions: The changes in stratification are particularly acute in polar regions, where the melting of ice caps is altering the salinity balance and reinforcing the stratification of the water column.
Activity: Create a positive feedback cycle diagram sowing the impact of global warming on ocean temperatures
Case Study:Greenland and the Effects of Ice Melt
The melting of ice caps has led to significant changes in the salinity of the surrounding waters. The reduction in salinity has intensified stratification, particularly in the North Atlantic. The decrease in vertical mixing has implications for global ocean circulation, as Greenland waters play a crucial role in driving global currents that help regulate Earth's climate.
Application of skills: Extract data from a database and analyse data on water temperatures with oxygen
and salinity concentrations using an appropriate statistical test.
and salinity concentrations using an appropriate statistical test.
- Reference data from US National Oceanic and Atmospheric Administration (NOAA), NASA Scientific Visualization Studio and the European Space Agency.
upwelling
4.1.13 Upwellings in oceans and freshwater bodies can bring cold, nutrient-rich waters to the surface.
- Define upwelling and explain how it is caused by the displacement of surface waters
- Explain how upwelling contributes to increased marine productivity and the growth of phytoplankton
Upwelling is a vital oceanographic and freshwater process where cold, nutrient-rich waters from the depths rise to the surface. This vertical movement occurs in response to surface waters being displaced by wind, which pulls deeper waters upward. Upwellings play a crucial role in supporting marine and freshwater ecosystems by replenishing surface waters with nutrients that promote biological productivity.
How Upwelling Works
Upwelling is driven by a combination of wind action and the displacement of surface waters:
Upwelling can occur in both marine and freshwater environments:
How Upwelling Works
Upwelling is driven by a combination of wind action and the displacement of surface waters:
- Wind Action: Winds blowing across the surface push surface waters away, often due to the Coriolis effect in oceans or other factors in freshwater bodies.
- Vertical Movement of Cold Water: As the surface water moves, deeper, colder, and nutrient-rich water rises to replace it, creating an upwelling zone.
Upwelling can occur in both marine and freshwater environments:
- In Oceans: Upwellings typically happen along coastlines, especially along western coasts where winds push surface water offshore, bringing deep waters to the surface.
- In Freshwater Bodies: Seasonal upwellings can occur in stratified lakes, especially during periods of strong wind or temperature changes, bringing nutrients to the upper layers.
https://oceantracks.org/library/the-north-pacific-ocean/upwelling-and-the-california-current
The Importance of Mixing in Upwellings
Upwelling is a form of vertical mixing, which is critical for the health of aquatic ecosystems. This mixing process circulates nutrients and gases throughout the water column, sustaining marine and freshwater life at all levels:
Upwelling is a form of vertical mixing, which is critical for the health of aquatic ecosystems. This mixing process circulates nutrients and gases throughout the water column, sustaining marine and freshwater life at all levels:
- Nutrient Delivery: Upwelling waters are rich in nutrients like nitrogen and phosphorus, which have accumulated in the deep waters from decomposing organic matter. These nutrients are essential for the growth of phytoplankton, the foundation of the marine food web.
- Oxygen Transport: In some cases, upwelling can also bring oxygenated water to deeper layers, supporting marine organisms living in these regions.
Seasonal Cycles of Upwelling
Upwellings are often seasonal in nature, influenced by climatic cycles and changes in wind patterns:
Ecological Importance of Upwellings
ENSO and Upwelling
The El Niño-Southern Oscillation (ENSO) is a natural climate cycle that affects ocean conditions worldwide:
Upwellings are often seasonal in nature, influenced by climatic cycles and changes in wind patterns:
- In Stratified Lakes: In temperate lakes, seasonal upwelling can occur during periods of strong winds, especially during autumn turnover, when the temperature differences between surface and deep water diminish, allowing for vertical mixing and nutrient redistribution.
- Upwelling and ENSO (El Niño-Southern Oscillation): ENSO cycles, particularly during the La Niña phase, can lead to strong coastal upwelling in regions like the Pacific Ocean. During these events, nutrient-rich waters rise to the surface, boosting marine productivity.
Ecological Importance of Upwellings
- Boosting Marine Productivity:
- Upwelling zones are among the most productive areas of the ocean due to the influx of nutrients that support massive phytoplankton blooms. These blooms, in turn, fuel higher trophic levels, including fish, marine mammals, and seabirds.
- Example: The Peru Current along the western coast of South America is an area of constant upwelling that supports one of the world's richest fisheries.
- Supporting Biodiversity:
- The cold, nutrient-rich waters that come to the surface during upwelling events provide the energy needed to sustain a variety of marine species. Biodiversity tends to be higher in regions affected by frequent upwelling due to the increased availability of food and habitat.
- Impact of Upwelling on Fisheries:
- Many of the world's most important fisheries rely on upwelling zones, as the influx of nutrients supports large populations of fish. However, changes in upwelling patterns due to climate variability, such as ENSO events, can lead to shifts in fish populations, affecting the livelihoods of coastal communities.
ENSO and Upwelling
The El Niño-Southern Oscillation (ENSO) is a natural climate cycle that affects ocean conditions worldwide:
- During El Niño, upwelling in the Pacific Ocean weakens, reducing the supply of nutrients to surface waters. This can lead to a drop in marine productivity and fish stocks.
- During La Niña, upwelling intensifies, bringing nutrient-rich waters to the surface, which boosts marine productivity.
https://www.noaa.gov/jetstream/tropical/enso/enso-patterns
Case Study: The Humboldt Current Upwelling
One of the most well-known upwelling systems is the Humboldt Current off the coast of South America. Winds drive surface water offshore, allowing nutrient-rich deep water to rise. This upwelling supports one of the most productive fisheries in the world, supplying a significant portion of global fish catch.
One of the most well-known upwelling systems is the Humboldt Current off the coast of South America. Winds drive surface water offshore, allowing nutrient-rich deep water to rise. This upwelling supports one of the most productive fisheries in the world, supplying a significant portion of global fish catch.
ocean circulation
4.1.14 Thermohaline circulation systems are driven by differences in temperature and salinity. The resulting differences in water density drives the ocean conveyor belt, which distributes heat around the world and thus affects climate.
- Explain the key factors that drive the global ocean conveyor belt.
- Outline how the global conveyor belt distributes heat around the world and affects weather.
image from www.sciencedaily.com
The thermohaline circulation is a global system of ocean currents driven by differences in temperature and salinity. These differences create variations in water density, which in turn drive the movement of water across vast distances, affecting climate patterns worldwide. The thermohaline circulation is also referred to as the ocean conveyor belt, which plays a critical role in distributing heat around the planet and influencing global climate systems.
How Thermohaline Circulation Works
Thermohaline circulation is based on the principle that water density is affected by two factors:
Thermohaline circulation is based on the principle that water density is affected by two factors:
- Temperature: Cold water is denser than warm water.
- Salinity: Water with higher salinity is denser than less salty water.
image from www.indiana.edu
The Ocean Conveyor Belt
The ocean conveyor belt is a continuous global loop of water movement that transfers heat and affects regional climates. This system circulates warm water from the equator to the poles and returns cold, dense water back to the equator via deep ocean currents. One of the most important parts of this system is the North Atlantic conveyor belt.
The ocean conveyor belt is a continuous global loop of water movement that transfers heat and affects regional climates. This system circulates warm water from the equator to the poles and returns cold, dense water back to the equator via deep ocean currents. One of the most important parts of this system is the North Atlantic conveyor belt.
- Surface Currents: Warm surface waters from the equator are transported northward by wind-driven currents. These waters cool as they move toward higher latitudes.
- Evaporation and Increased Salinity: As the warm waters approach the North Atlantic, they lose freshwater through evaporation, which increases their salinity and density. The combined effects of colder temperatures and higher salinity make the water heavier.
- Sinking and Deep Currents: In the North Atlantic, particularly near Greenland and Iceland, the now cold, salty, and dense water sinks, forming deep ocean currents. This sinking water forms part of the global conveyor belt and begins a journey back toward the equator.
- Return Flow: The deep currents carry cold water toward the equator, where it gradually warms, rises, and re-enters the surface circulation, completing the cycle.
image from www.windows2universe.org
Impact of Freshwater Input on the North Atlantic
The North Atlantic conveyor belt is sensitive to changes in salinity and temperature:
The Importance of the Conveyor Belt for Global Climate
Potential Disruptions to the Thermohaline Circulation
The system is vulnerable to changes caused by global warming:
The North Atlantic conveyor belt is sensitive to changes in salinity and temperature:
- Freshwater Input from Rivers and Ice Melt: Rivers and melting ice caps, especially from Greenland, introduce low-salinity, low-density freshwater into the North Atlantic. This can disrupt the thermohaline circulation by making the water less dense and slowing down the sinking process.
- Climate Implications: If the input of freshwater continues to increase due to climate change, it could weaken the conveyor belt, leading to changes in heat distribution and global climate patterns. Regions that rely on the ocean's heat distribution, like Western Europe, could experience cooling, while other areas might warm.
The Importance of the Conveyor Belt for Global Climate
- The thermohaline circulation acts as a climate regulator by redistributing heat around the world.
- For example, the warm surface currents carried by the Gulf Stream and North Atlantic Drift help maintain relatively mild temperatures in Western Europe, even at high latitudes.
- Without the conveyor belt, regional climates could shift dramatically, leading to colder winters in Europe and more extreme weather patterns globally.
Potential Disruptions to the Thermohaline Circulation
The system is vulnerable to changes caused by global warming:
- Increased Ice Melt: As global temperatures rise, the melting of polar ice caps introduces more freshwater into the oceans, reducing salinity in key areas of the North Atlantic. This disrupts the sinking of dense water and weakens the conveyor belt.
- Increased Precipitation: Climate change may also lead to more rainfall in the North Atlantic region, further reducing salinity and impacting the thermohaline circulation.
Case Study: The Role of the North Atlantic Conveyor Belt
The North Atlantic conveyor belt, also known as the Atlantic Meridional Overturning Circulation (AMOC), is a crucial component of the global thermohaline system. Changes in the AMOC could lead to regional climate impacts, including:
The North Atlantic conveyor belt, also known as the Atlantic Meridional Overturning Circulation (AMOC), is a crucial component of the global thermohaline system. Changes in the AMOC could lead to regional climate impacts, including:
- Cooling in Europe: If the AMOC slows down or collapses, Western Europe could experience significantly colder winters.
- Sea-Level Rise: A weakened AMOC may contribute to regional sea-level rise, particularly along the eastern coast of the United States.
- Global Climate Impacts: Disruptions to the AMOC could also affect monsoon patterns and rainfall distribution in tropical and subtropical regions, with potentially severe consequences for agriculture and water resources.
https://skepticalscience.com/sea-change-understanding-atlantic-conveyor.html
Key Terms
|
surface water
hydrology rivers advection salinization irrigation evaporation evapotranspiration HL ONLY polarity cohesion adhesion transparency heat capactiy haline carbon sink thermohaline inorganic carbonates upwelling el nino la nina turnover time downwelling stratification water density |
salt water
soil moisture hydroelectric hydrologic cycle consumptive water condensation stream flow carbon sequestration |
fresh water
aquifer drought watershed freezing melting ground water |
ground water
ponds zone of saturation transpiration dissolved oxygen sublimation hydrosphere |
lakes
water table recharge zone salinization percolation infiltration |
Classroom Materials
| Subtopic 4.1 Water Systems Presentation.pptx |
| Subtopic 4.1 Water Systems Workbook.docx |
Water Cycle Diagram worksheet
Global Water Use
Home Water Use activity
Calculate Your Water Footprint
Practice Problems: Estimating Water Budgets
Bottle Water Case Study
Map of Worldwide Domestic Water Use - World Mapper
World Map of Industrial Water Use - World Mapper
World Map of Agricultural Water Use Map - World Mapper
Map Worldwide Poor Water Quality - World Mapper
Map of Worldwide Water Availability - World Mapper
Map of Worldwise Water Depletion - World Mapper
Case Studies
- One detailed example of human influence on the hydrological cycle with regards to agriculture, deforestation and/or urbanization (eg. the Colorado River and agriculture)
Correct use of terminology is a key skill in ESS. It is essential to use key terms correctly when communicating your understanding, particularly in assessments. Use the quizlet flashcards or other tools such as learn, scatter, space race, speller and test to help you master the vocabulary.
Useful Links
Topic 4.1, 4,2, 4,3 Water Systems - NicheScience
Interactive Tool Looking at the Path of a Raindrop in the United States
Interactive Tool Looking At Water Availability and Usage Around the World
Characteristics of Water - Sumanis
USGS Water
Aerial Photos of Water
Water Use Statistics how much water is being consumed in the world this year - WorldOMeter
Cost of Removing Nitrates from Ground water - Essex University
Water and Development - Global Issues
Water Cycle animation - Earthguide
Water Cycle - McGraw Hill
Water Consumption Calculator - CSG Network
How Much Is Your Daily Indoor Water Use - USGS
Water Use Calculator - Water Budgets
Water Footprint Calculator - Grace
Ground Water Animation - TechAlive
In The News
MAP: The World's Water Scarcity Problem Is Bad And Getting Worse - Business Insider May 13, 2014
Freshwater Stories - National Geographic
Water - NPR Science Friday Podcast 21 Mar 2008
International-mindedness
- Many hydrological cycles are shared by various nations. This can lead to international disputes.
TOK
- The hydrological cycle is represented as a systems model—to what extent can systems diagrams effectively model reality, given that they are only based on limited observable features?
Video Clips
Julia Roberts, Harrison Ford, Kevin Spacey, Edward Norton, Penélope Cruz, Robert Redford and Ian Somerhalder all join forces to give nature a voice.
Hank again on cycles. Focus on Hydrological Cycle
In this video Paul Andersen explains the vital role that water plays in the processes on the Earth's surface. Water has several unique properties including high heat capacity, transparency, polarity and the ability to change the chemical behavior of the mantle. The Earth is largely a water planet but most of the water is found in the oceans or locked in ice. Water is a powerful erosive force on the planet.
The Story of Bottled Water, released on March 22, 2010 (World Water Day) employs the Story of Stuff style to tell the story of manufactured demand—how you get Americans to buy more than half a billion bottles of water every week when it already flows from the tap. Over five minutes, the film explores the bottled water industrys attacks on tap water and its use of seductive, environmental-themed advertising to cover up the mountains of plastic waste it produces
The short animation called "Ever wondered where the rain goes?" demonstrates how changes to the natural water cycle caused by development can be positively managed, and, how SuDS turns this challenge into an exciting opportunity contributing to better places.
The oceans are mostly composed of warm salty water near the surface over cold, less salty water in the ocean depths. These two regions don't mix except in certain special areas. The ocean currents, the movement of the ocean in the surface layer, are driven mostly by the wind. In certain areas near the polar oceans, the colder surface water also gets saltier due to evaporation or sea ice formation.
Have you ever wondered what El Niño is? Trace was curious and decided to do some digging to figure out what exactly it is.
Human Impact on Water
