water and carbon cycle

Define an open system in the context of Earth's subsystems.

A system where both energy and matter can enter and leave, such as forests or coastal regions.

What distinguishes a closed system from an open system?

In a closed system, energy can enter and leave, but matter cannot.

Why is Earth considered a closed system regarding the water cycle?

Because energy from the sun enters and heat radiates into space, but the total amount of matter (water) remains constant and is not significantly added or removed.

What is dynamic equilibrium?

A state where processes continue without significant overall changes, maintaining an average balance despite small fluctuations in inputs and outputs.

Explain the difference between positive and negative feedback.

Positive feedback amplifies change, moving the system away from its original state, while negative feedback counteracts change, returning the system toward its original state.

Give an example of negative feedback in the climate system.

Increased temperature leads to more water vapour, which increases cloud formation, reflecting more sunlight into space and ultimately decreasing temperature.

Name the five major subsystems of Earth.

Cryosphere, Lithosphere, Biosphere, Hydrosphere, and Atmosphere.

What is the primary store of Earth's water?

The oceans, which hold approximately 97% of Earth's water.

What percentage of Earth's water is freshwater?

Less than 3%.

Where is the majority of Earth's freshwater stored?

In the cryosphere (ice sheets and glaciers), accounting for 69% of freshwater.

What determines whether water state changes involve gaining or losing energy?

Gaining energy (from solar radiation) causes melting or evaporation; losing energy to surroundings causes freezing or condensation.

Define potential evapotranspiration (PET).

The maximum possible water loss that could occur under ideal conditions.

Why is actual evapotranspiration low in arid regions despite high PET?

Because actual evapotranspiration is limited by the lack of available water, even though the heat potential for evaporation is high.

What is the role of cloud condensation nuclei?

They provide surfaces for water vapour to condense into tiny droplets during cloud formation.

List three types of precipitation and their causes.

Frontal (warm air meets cold air), Orographic (air forced over mountains), and Convective (ground heating causes air to rise).

How does temperature influence the cryosphere?

It dictates the balance between accumulation (snowfall) and ablation (melting); colder periods favor accumulation, while warmer periods favor ablation.

What is a drainage basin?

An area of land (catchment) where all precipitation eventually flows into a single river system.

What is a watershed?

The boundary marking the edge of a drainage basin, separating it from adjacent basins.

Define the water table.

The upper limit of the zone of saturation, where all soil or rock pores are filled with water.

What is an aquifer?

A body of porous rock that holds and transmits groundwater.

What is interception in the water cycle?

Water that is captured by vegetation or man-made structures before it reaches the ground.

How do interactions between subsystems create a cascading system?

Outputs from one subsystem act as inputs for another, such as water evaporating from the hydrosphere into the atmosphere.

What is the difference between an isolated system and a closed system?

An isolated system allows neither energy nor matter to leave, whereas a closed system allows energy to enter and leave.

What factors influence the rate of evaporation?

Solar radiation intensity, water availability, air temperature, and humidity.

Why is the availability of freshwater limited for human use?

Because water must be both physically reachable and economically viable to extract or treat.

What is the difference between infiltration and percolation?

Infiltration is water soaking into the soil surface, while percolation is the downward seepage of water through soil layers to the water table.

Define throughfall and stemflow.

Throughfall is water dripping from plant parts after interception; stemflow is water running down plant stems or trunks to the ground.

What is baseflow in a river system?

Groundwater seeping into rivers through banks and beds, which sustains river flow during dry periods.

How is the water balance calculated?

Inputs (precipitation) minus outputs (river discharge and evapotranspiration).

What characterizes a water surplus during the wet season?

Precipitation exceeds evapotranspiration, leading to filled ground stores, increased surface runoff, and rising river levels.

What is river discharge and how is it measured?

The volume of water passing a point over time, measured in cubic metres per second (cumecs).

What does a flood (storm) hydrograph represent?

The change in river discharge during and immediately after a storm event.

Define 'lag time' in the context of a hydrograph.

The time difference between peak rainfall and peak river discharge.

What does a 'shallow falling limb' on a hydrograph suggest?

It suggests that water continues to flow into the river from storage areas long after rainfall has ceased.

What is bankfull discharge?

The level at which water reaches the top of the river channel; exceeding this level causes flooding.

List three characteristics of a 'flashy' hydrograph.

Rapid runoff, short lag time, and high peak discharge.

How does drainage basin shape affect hydrograph response?

Circular basins produce flashier hydrographs because water arrives at the measuring point simultaneously, whereas long, narrow basins stagger water arrival.

How do impermeable surfaces affect the water cycle?

They prevent infiltration, which increases surface runoff and peak discharge.

What are the primary hydrological effects of winter on a river system?

Saturated ground leads to flooding, increased channel flow due to less evaporation, and reduced interception due to loss of leaves.

How do droughts impact the water cycle?

They reduce water stores, cause vegetation death (reducing transpiration/interception), and lead to soil drying, which decreases throughflow.

What is the impact of deforestation on the water cycle?

It reduces interception and infiltration, which increases surface runoff and flood risk.

How does urbanization alter the water cycle?

It increases impermeable surfaces, decreasing infiltration and increasing surface runoff, often overwhelming drainage systems.

How do farming practices like ploughing affect infiltration?

Ploughing breaks up the soil, which enhances infiltration and reduces surface runoff.

What is the effect of livestock grazing on soil hydrology?

Grazing animals compact the soil, which decreases infiltration and increases surface runoff.

What are the consequences of excessive water abstraction?

It depletes natural stores like lakes and rivers, reduces river discharge, and can lead to environmental collapse, such as increased salinity.

Where is the majority of Earth's carbon stored?

In the lithosphere, specifically in sedimentary rocks like limestone (99.9%).

How is carbon stored in the cryosphere?

Mainly in permafrost, where frozen decomposing organisms trap carbon.

What is the role of the biosphere in the carbon cycle?

It stores carbon within the tissues of living organisms.

How does climate change influence the water cycle?

It increases temperatures, rainfall intensity, and sea levels, leading to more frequent extreme weather events like droughts and floods.

What is the difference between throughflow and interflow?

Throughflow moves through soil layers, while interflow moves through permeable rock layers above the water table.

What is a river regime?

The variation in a river's discharge throughout the course of a year.

What is the primary form of carbon in the atmosphere?

Carbon dioxide (CO2), with trace amounts of methane (CH4).

How does photosynthesis transfer carbon?

Plants and phytoplankton use solar energy to convert atmospheric CO2 and water into glucose, moving carbon into biomass.

What is the role of respiration in the carbon cycle?

Living organisms break down glucose for energy, releasing CO2 and sometimes CH4 back into the atmosphere.

How does combustion affect the carbon cycle?

It burns organic material, transferring carbon from biomass directly into the atmosphere.

What happens to carbon during decomposition?

Bacteria and fungi break down dead organisms, releasing CO2 and CH4 into the atmosphere, while some carbon is incorporated into soil as humus.

How are hydrocarbons formed over millions of years?

Through the burial and compaction of decomposed plants and animals under high pressure.

What is the process of carbon sequestration?

The long-term capture and storage of carbon in sedimentary rocks or fossil fuels, keeping it locked away until released by processes like combustion.

Why are peatbogs significant in the carbon cycle?

They act as a major carbon sink, storing huge amounts of carbon and helping to mitigate climate change.

How can damaged peatbogs be restored?

By rewetting them, which involves blocking drainage ditches and raising the water table.

What defines a carbon source versus a carbon sink?

A carbon source releases more carbon than it absorbs, while a carbon sink absorbs more carbon than it releases.

How do wildfires influence the carbon cycle?

They rapidly transfer carbon from the biosphere to the atmosphere, though they may have a neutral long-term effect by promoting new plant growth.

What is the impact of volcanic activity on the carbon cycle?

It releases carbon stored in magma as CO2 into the atmosphere and can temporarily reduce incoming solar radiation through ash and aerosols.

What are sunspots and how do they affect climate?

Dark spots on the sun's surface associated with increased solar radiation; their 11-year cycle can influence global temperatures.

What percentage of human carbon emissions comes from hydrocarbon fuel extraction and burning?

90%.

How do farming practices contribute to greenhouse gas emissions?

Livestock release CO2 and CH4 through digestion, and rice fields produce CH4 and nitrous oxide from waterlogged soil microbes.

Why is deforestation a significant contributor to global CO2 emissions?

It releases stored carbon through burning and reduces the biosphere's overall capacity to sequester carbon.

How does urbanisation affect the carbon cycle?

It removes vegetation (reducing storage) and involves concrete production, which is a major source of anthropogenic CO2 emissions.

What is the impact of warmer temperatures on permafrost?

It causes permafrost to thaw, releasing stored carbon into the atmosphere.

How does increased CO2 absorption affect ocean environments?

It raises ocean acidity, which harms marine life and can reduce the ocean's capacity to absorb CO2 as waters warm.

What is the 'greenhouse effect'?

The process where greenhouse gases trap reflected heat in the atmosphere, warming the planet; without it, Earth would be 33 degrees colder.

What is an example of positive feedback in the water cycle?

Increased temperatures lead to higher evaporation rates, increasing water vapour, which is a greenhouse gas that further raises temperatures.

What is an example of negative feedback in the carbon cycle?

Increased atmospheric CO2 promotes plant growth, which sequesters more carbon through photosynthesis, helping to lower CO2 levels.

What are two major predicted impacts of climate change on water resources?

Altered precipitation patterns (wetter regions getting wetter, drier regions facing drought) and increased extreme weather events.

Why do less developed countries face disproportionate risks from climate change?

They often have fewer resources available to adapt to and recover from climate-related impacts.

What is Carbon Capture and Storage (CCS)?

A mitigation strategy that captures CO2 emissions from industrial processes and stores them underground to prevent atmospheric release.

What is the purpose of international agreements like the Paris Agreement?

To unite countries globally in the effort to reduce greenhouse gas emissions.

How do carbon trading schemes work?

Countries and companies are allocated emission limits and can trade credits to encourage overall reductions in CO2 output.