p10 Flashcards
What are the consequences of rising temperatures?
Ocean Acidity
Rising temperatures = increased rates of evaporation
This impacts on:
Precipitation patterns
River
Water stores (cryosphere and drainage basin stores)
Precipitation Patterns
Existing weather patterns will get stronger (wet places will get wetter and dry places will get drier).
This is because warm air traps more water – scientists expect more water to fall on wet places.
River Regimes
‘the annual variation in discharge or flow, at a particular point’.
The character of the regime is influenced by climate.
Increased temperatures = more snow/glacier melt, and an increased in the amount and intensity of precipitation.
Water Stores
Cryosphere has been losing mass as ice sheets and glaciers melt.
Arctic temperatures have risen twice as fast as global averages in the past 20 years.
This means huge implications for ocean currents, air circulation, sea level rise and flooding.
Case Study: Yukon
Yukon is a territory in the far northwest of Canada and a significant part of it lies within the Arctic Circle.
Like most Arctic and sub-artic areas it has seen temperatures rise sharply, and forecasts are for continued warning.
The increasing temperature has implications for precipitation patterns, river regimes and water stores:
Increasing temperatures lead to increased evaporation and atmospheric water vapour.
Across Yukon, winter precipitation increased between 1950 and 1998. However a greater proportion fell as rain in spring and less as snow (as previously).
Snowmelt now begins earlier and snow cover is decreasing. This alters river regimes, bringing earlier peak flows to most river basins.
Between 1958 and 2008, the total ice area shrank by 22% and, as glaciers recede, streamflow is decreasing – despite an initial increase in meltwater.
Climate change is leading to thawing of permafrost – so water penetrates deeper into the soil, instead of forming surface runoff.
Since 2000, inflows to the Yukon river have increased by 39% due to increasing temperature and precipitation.
As the permafrost thaws, climate change could increase the amount of groundwater.
Case Study: Arctic
Over the last 20 years the ice sheets in the Antarctic and Greenland ice sheets have been losing mass and the Arctic sea ice and northern hemisphere spring snow cover have continued to decrease in extent and thickness.
The Arctic acts as an early warning system, acting as a barometer of the environmental impacts resulting from fossil fuel use.
In the past few decades, average Arctic temperatures have risen twice as fast as global averages: 3-4- degrees in Alaska and north-west Canada.
Which could soon increase another 4-5 degrees over land, and 7 degrees over the ocean.
how impacts of rising temperatures Effects on the water cycle
Warm water flowing into the Arctic from the Pacific and Atlantic.
Rising local temperatures – increased evaporation.
Shrinkage of sea ice; the Arctic ice cap averages only 3m thick and melting is increasing faster than anticipated.
Run-off of fresh, cold water which will alter marine ecosystems and food chains dependent on the saline waters; predicted to affect areas outside the Arctic Ocean by 2100.
Funnelling of more cold water into the oceanic conveyor belt.
how impacts of rising temperatures Effects on the carbon cycle
Increased or new emissions of: CH4 (methane) from destabilisation of wetlands and sea floor deposits containing methane hydrate, stored for thousands of years.
Increased or new emissions of: mainly CH4 and some CO2 from thawing permafrost.
Increased or new emissions of: CO2 from increased forest fires as boreal forests dry out; they may also absorb CO2 and CH4 from the atmosphere.
What is the problem with trying to project the future impacts of global warming?
There is uncertain confidence in many predictions due to lack of valid data in climate models from which to project the cascade and feedback effects in Arctic systems.
E.g. A team of scientists believe that the twentieth century was neither drier not wetter for half then globe than previously.
Their research showed that temperature increases in the 20th century may not have affected rainfalls as much as they had thought – uncertain futures, difficult to predict.
Using examples, explain the impacts of rising temperatures to water stores (8)
One impact of rising temperatures to water stores is the change in river regimes. The change in a rivers discharge or flow is a consequence of the changing climate linked to rising temperatures. In Yukon rising temperatures have resulted in increasing amounts of evaporation leading to winter precipitation. However the majority of this precipitation now falls as rain in the spring as opposed to snow. This has resulted in peak discharge occurring earlier than normal for many river basins which has meant that some inflows to rivers in Yukon have increased by 39%. This has meant that river discharge has been considerably higher which has meant the rivers as water stores have increased which means that areas will be more susceptible to flooding due to the increase in water volume.
A second impact of rising temperatures to water stores is the reduction in water being stored in ice masses. In the past few decades, average Arctic temperatures have risen 3-4 degrees - twice as fast as global averages which has resulted in ice masses such as the Greenland ice sheet losing a substantial amount of mass in the past 20 years. It was reported in the Intergovernmental Panel on Climate Change 2014 report that the Arctic Ocean could be ice free by 2037 due to warming ocean waters and a reduction in sea ice. This will result in a change to where water is stored as melting ice will cause more water to be stored in the oceans rather than as ice in glaciers and ice sheets which means that as a water store, the ocean will get bigger resulting in global sea level rises.
Threats to Ocean Health
The well-being and survival of many coastal communities depends on the health of the ocean and marine ecosystems, especially in developing countries.
Mangroves
Mangroves are found along tropical and sub-tropical coasts of Africa, Australia, Asia and the Americas.
They sequester almost 1.5 metric tonnes of carbon per hectare, per year.
Their soils consist of thick organic layers of litter, humus and peat, which contain high levels of carbon – over 10%.
As they are submerged twice a day by high tides their soils are anaerobic (without oxygen), bacteria and microbes can’t survive without oxygen so decomposition of plant matter is slow – meaning little carbon is respired back into the atmosphere so is stored for thousands of years.
Benefits of mangroves
Mangroves can provide many benefits to our communities:
they stabilise the coastline against erosion.
They provide protection and shelter against extreme weather (e.g. storms winds and floods) and tsunamis, by absorbing and dispersing surges.
They provide nurseries for coastal fish away from predators.
Human Activities on mangroves
We are draining and clearing mangrove forests for tourism, shrimp farming and aquaculture – this has accounted for over 25% of the loss of the forests.
Globally half of all mangrove forests have been lost since 1950.
According to Malaysian researchers, if just 2% of the world’s mangroves are lost, the amount of carbon released will be 50 times the natural sequestration rate.
Marine Species and the Fishing Industry
Benefits:
The FAO (Food and Agriculture Organisation) estimates that fishing supports 500 million people, 90% of which are in developing countries.
Fish provide 16% of the annual protein consumption for 3 billion people, and is the main source of cheap protein for 3 billion people.
Fish are the cultural choice of many wealthier countries e.g. Iceland and Japan, but a necessity for well-being in poorer countries e.g. Namibia, Ghana and Senegal.
Millions of small-scale fishing families depend on seafood for income as well as food; 60% of GDP is from fish and it provides essential protein in many of the 49 Small Island Development States such as St Lucia and the Maldives.
Coral reefs shelter 25% of marine species.
Tourism: Globally coral reefs are tourist attractions e.g. the Great Barrier Reef, Australia.
