Past freshwater changes

18 important questions on Past freshwater changes

What is the most diverse and highly impacted natural system? And why?

- Freshwater systems
- Very high extinction rates, because human uses and pollution takes their roll

The base of freshwater food chains is often occupied by?

Microorganisms
  • In terrestrial systems, this is most often centred in macroplants 

What are streams, rivers and lakes?

- Surface features whose existence and physical characteristics are very vulnerable to climate change
- Their existence is dependent on the balance of precipitation and evaporation
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Are continuous range shifts possible in fresh water systems?

No

How are lake low and high stands indicated?

By geochemical and biological changes in sediments, such as increased precipation of minerals in drying conditions or increased biological traces in times of high water and high productivity

What are mega droughts?

Droughts lasting from decades to centuries that bring prolonged harsh conditions to large areas

What can you see from lake records?

- Regional temperatures
- Precipitation changes

What did glacial ice sheets do?

- They deflected the jet stream southward, resulting in increased precipitation and higher lake levels

What are varves? And what can be measured?

- Annual layers created by biological or biogeochemical processes
- Counting the number of varves associated with the transition at the end of the Younger Dryas provides a high-resolution estimate of its duration

What do lakes contribute knowlegde to?

- Of their own physical/biological changes
- Changes in regional climate
- Changes in vegetation
- Interregional synchrony
- Global magnitude
- Cycles
- Speed of change

What are changes importanton short and long term scales?

Alterations in:
  • Streamflow
  • Temperature
  • Watershed fragmentation
  • Capture
  • Lake drying and filling
  • Lake thermal zonation  

When do changes in streamflow result?

When precipitation and evapotranspiration vary

What happens once air masses have lost moisture in major storm events?

Warmer conditions draw more water from soils -> extent droughts -> even dryer places

When does streamflow increase?

With increased precipitation and decrease in drought

How wil the timing of streamflow vary?

With changes in snowmelt and storm intesnsity
- Snowmelt will be erarlier due to increased temperature -> earlier season peaks in flow followed by late season flows that are reduced relative to current conditions

How does stream following air temperature?

With shallower streams responding more quickly to changes in temperature

Which streams dominate stream and river systems?

- Short shallow streams (first / second order streams), so the proportion of temperature sensitive waterways is high

What will be more sensitive to changes in air temperature?

Streams and rivers with greaster contributions from surface water relative to groundwater

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