Climate Change & Glacial Mass Balance (Edexcel A Level Geography): Revision Note
Exam code: 9GE0
Role of Climate Change
Although some of the world's glaciers are advancing and in positive mass balance, climate change has led to unprecedented levels of melting
This is resulting in negative mass balance in cold environments
Periglacial areas will see melting permafrost
This will change the ecosystem and biodiversity of the tundra
Melting of ice and permafrost will likely change the water cycle
Many people depend on for their main water supplies (Peruvian Andes supplies 30% of all water to the communities in the mountains)
As glaciers shrink, so will water supplies after a period of gain as the glacier melts
Increased river discharge increases flood risk during spring/summer melt, particularly with extreme heating causing ice melt spikes
HEP dam operations become redundant with lower meltwater levels
Lower velocities of meltwater cannot remove pollutants
Leading to lower water quality
Sediment yields change
They can increase due to excess sediment build-up, leading to low flow rates and sudden flood bursts
Or they can decrease, leaving outwash plains exposed and easily eroded
Case Study
The Himalayan glaciers
The Himalayas are often called the ‘Third Pole’ because they hold more ice than anywhere outside the Arctic and Antarctic
Their meltwater feeds three huge rivers — the Ganges, Indus and Brahmaputra
Together these rivers supply water to around 1.9 billion people, about a quarter of the world’s population
As the climate warms, the glaciers here are melting quickly:
The Gangotri glacier, the source of the Ganges, has retreated about 1.7 km since 1935
It is now retreating by roughly 20–30 m per year
This melting causes several problems downstream:
Water supply: rivers gain water at first, but shrink in the long term as the glaciers disappear
Flooding: faster summer melt raises river levels and increases flood risk
Outburst floods: a glacial lake can burst suddenly (a glacial lake outburst flood) — in October 2023 the South Lhonak Lake flood in Sikkim killed over 100 people and destroyed a hydroelectric dam
Sediment and water quality: changing flows alter how much sediment the rivers carry, affecting farmland and drinking water downstream
Examiner Tips and Tricks
Being synoptic in your exam is an important skill the examiner is looking for. Therefore, remember to draw on knowledge of climate change from other parts of the course, such as cold environments as a carbon sink and the impact it has on the carbon cycle etc.
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