Water Cycle Pack C Flashcards
Why does the amount of water in the sea versus the amount in ice change?
- Sea levels have risen and fallen significantly over geological time
- More snow = less water in oceans
What are eustatic changes?
Changes to sea levels when water is locked away as ice, and it rises as temperatures warm
What causes the changes in the amount of water stored in ice and the sea?
- Seasons
- Sunspots
- Volcanic eruptions
- Climatic warming
- Milankovitch cycles (tilt, eccentricity, precession)
- Tectonic activity (uplift of mountains like the Himalayas or Alps increases cryospheric storage in glaciers)
- Pangea separating (positive feedback cycle in Antartica)
What is Snowball Earth?
- 650 and 750 million years ago
- Scientists believe that Earth was completely covered in ice
- Storage of water in the cryosphere would have been much higher than at present
What is Hothouse Earth?
- 100 million years ago in the world of the dinosaurs
- Carbon dioxide levels reached 800 ppm (double that of today)
- Little or no ice on Earth and polar regions had forests
What causes a cyclone?
- 30° latitude north or south of the equator
- Over warm tropical oceans temperature is at least 27 °C
- Coriolis force
- Low wind shear
- Rising air creates an area of low pressure
- Cooler air rushes into the low-pressure area creating wind
- Rising air cools and forms clouds
- Spinning winds move the cyclone across the ocean but it loses strength as it moves inland
What is an example of a cyclone?
- Cyclone Nargis May 2008
- Category 1 on the Saffir-Simpson scale
- Category 2 winds
- 600mm of rainfall in a few days
- 3.5m to 4m storm surge
- 14,000km2 of land flooded
What causes the monsoon?
- Land heats up faster than water
- Air above ground heats up faster than air above the sea
- Warm air expands and rises, while cooler air from the ocean rushes in to replace it
- This moist air condenses into clouds and falls as rain
What is an example of a monsoon?
- 2024 Monsoon in India
- 8% more rain than historical average
- Roughly 90cm of rain
- June to September
- Western and Central regions received 90% of their total annual precipitation
What effects does El Nino have on the water cycle?
- Ocean temperatures increase
- Speed and strength of ocean currents change
- Extreme weather events (e.g. typhoons and cyclones) are more likely
- Record warm years
- Monsoon in India may be weaker and other parts of Asia drier
- Australia may be drier and there are often drought conditions in Africa
How does climate change affect the water cycle?
- Increased evaporation leads to more frequent and intense storms
- Storm-affected areas are likely to experience more precipitation
- Areas away from storm tracks are likely to experience less precipitation and droughts
- Changes to monsoon precipitation are expected, varying by region
- Precipitation is likely to increase in high latitudes and decrease over large parts of the subtropics
- Coastal areas will see continued sea level rise, contributing to more frequent and severe coastal flooding
What types of soil store more water and why?
Clay:
- Heavy and high in nutrients
- Wet and cold in winter, baked dry in summer
- Small pore spaces reduce infiltration and throughflow
- More surface runoff
- Once water enters, it can stay there
Sandy:
- Light, dry, warm, low in nutrients and often acidic
- Large pore spaces lead to rapid infiltration and throughflow
- Drainage is fast so there is less flooding
Silt:
- Fertile and light
- Moisture retentive
- Easily compacted
Loams:
- Mixtures of clay, sand and silt
- Avoid the extremes of each
What are the 3 types of soil water storage and how much water do they store?
- Gravitational water storage holds the most but it drains right through to field capacity
- Field capacity is the amount of water that remains in soil, once all gravity water has drained away
- This leads to capillary water storage, where water is held in micropores and plant roots can absorb it
- Wilting point is when there is insufficient water in the soil to replace the water that plants lose through transpiration
- This leads to hygroscopic storage, where remaining water strongly adheres to soil particles
What does the water balance graph look like and why might it vary for different places?
- The balance between inputs and outputs of water to the soil
- In winter, precipitation exceeds evaporation and soil moisture is recharged
until there is a soil moisture surplus - This is now available to supply rivers
- In summer, evaporation exceeds precipitation so soil water is utilised
- By the second half of summer, there is a soil moisture deficit
- In autumn, precipitation increases and evapotranspiration falls so soil moisture is recharged
