OCR A-Level Geography H481
Coastal Landscapes
Glaciated Landscapes
Dryland Landscapes
Earth’s Life Support Systems
Changing Spaces; Making Places
Trade in the Contemporary World
Global Migration
Human Rights
Power and Borders
Climate Change
Disease Dilemmas
Exploring Oceans
Future of Food
Hazardous Earth
Geographical Skills
Climate Change
Retreating ice, shrinking snow cover and rising sea level
- 2 things to know
- Component 03
Overview
Recall questions on retreating valley glaciers and mass balance, the effect of glacier loss on mountain water supply, ice loss from Greenland and Antarctica and how satellites measure it, sea level rise since 1900 and its acceleration, thermal expansion and meltwater, sea ice decline and albedo, falling snow cover, and thawing permafrost.
What you need to know
Answer each one before you reveal it.
Which two ice sheets are currently losing mass, and roughly how much does Greenland lose each year?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What has happened to the world's valley glaciers since the late 19th century?
Model answer
The great majority have thinned and retreated, and many of the smallest have disappeared entirely.
- 2
Explain in terms of mass balance why a glacier retreats.
Model answer
When ablation by melting and calving exceeds accumulation of snow over a run of years, the glacier loses mass overall and its snout retreats up the valley.
- 3
Give one serious consequence of glacier loss for people living in mountain regions.
Model answer
Rivers fed by glacial meltwater lose their dry-season flow, cutting the water available for irrigation, drinking and hydroelectricity in regions such as the Andes and the Himalaya.
- 4
Which two ice sheets are currently losing mass, and roughly how much does Greenland lose each year?
Model answer
Greenland and Antarctica are both losing mass, with Greenland shedding on the order of 250 gigatonnes a year in recent decades.
- 5
How do satellites measure the changing mass of an ice sheet?
Model answer
Paired satellites detect tiny changes in Earth's gravity field caused by the loss or gain of ice, while radar and laser altimeters measure changes in the height of the ice surface.
- 6
Explain how warm ocean water can accelerate ice loss from an ice sheet.
Model answer
Warm water reaching the underside of floating ice shelves thins them, weakening the buttressing that holds back the glaciers behind, so those glaciers flow faster into the sea.
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