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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.

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Key term

What has happened to the world's valley glaciers since the late 19th century?

Key term

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. 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. 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. 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. 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. 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. 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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