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212 PART IV • Deglacial Climate Change

TABLE 12.1 Approximate Volumes of Ice and Amounts of Water Stored in Glacial Ice
Sheets by Lowering Sea Level beneath Today’s Position

TSH:Sea level
Excess ice volume
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Ice sheet Location (million km ) Amount (m) Change (m) a
Laurentide East-central Canada 25–34 b 72–100 50–70
Cordilleran Western North America 1.8 5 3.5
Greenland Greenland 2.6 c 7 5
Britain England, Scotland, Ireland 0.8 2 1.5
Scandinavian Northern Europe 7.3 21 15
Barents/Kara Shelf north of Eurasia 6.9 20 14
East Antarctic Eastern Antarctica 13.3 d 9 6
West Antarctic Western Antarctica 16.5 d 18 13
Others Various 1.2 3 2
All ice sheets 55–64 155–183 109–129
a Net sea level changes are 30% smaller than the volumes of seawater removed from the ocean because
ocean bedrock rises when the weight of water is removed.
b The higher estimate shown is for a thick ice sheet like that in the CLIMAP maximum reconstruction;
the lower estimate is for a thin ice sheet.
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c Present volume of ice on Greenland is 3 million km .
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d Present volume of ice on Antarctica is 29 million km .
Source: Adapted from G. H. Denton and T. J. Hughes, The Last Great Ice Sheets (New York:
Wiley, 1981).

The most striking features of the CLIMAP recon- on Antarctica and Greenland across land exposed by the
struction are the continent-sized ice sheets covering fall in sea level. Expansion of mountain glaciers dramat-
North America as far south as 37°N latitude, Scandi- ically transformed the appearance of high terrain
navia down to 48°N, and the Arctic margins of Eurasia. around the world but contributed little to the change in
Today ice sheets on Antarctica and Greenland cover a ice volume. In some regions, such as Patagonia in
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combined area of about 14.2 million km , equivalent to southernmost South America, mountain glaciers merged
just under 3% of Earth’s surface area and about 10% of into small ice caps.
its land surface. The CLIMAP reconstruction of Earth The glacial world in the CLIMAP reconstruction was
at the last glacial maximum shows ice sheets covering an almost 4°C colder than Earth today. The North Atlantic
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area of 35 million km , equal to 7% of Earth’s total cooled by 8°C or more, and sea ice was more extensive
surface and 25% of the area of the continents. than it is today (see Figure 12–2B). Farther from the ice
The North American ice sheet was by far the largest sheets, the North Pacific cooled by a lesser amount, with
of the northern hemisphere ice sheets, accounting for expanded winter sea ice in the northwest. Sea ice also
over 55% of the volume of ice in excess of the amount advanced well beyond its present limits in the Southern
on Earth today (Table 12–1). This great ice sheet was Ocean, with a band of cooler ocean surface temperatures
roughly equivalent in volume to the ice sheet on mod- north of the expanded limit of sea ice around Antarctica.
ern Antarctica. Most of the ice in North America was in The CLIMAP reconstruction indicates low-latitude
the Laurentide ice sheet, centered on east-central ocean temperatures only slightly cooler than today’s and
Canada, with the rest in the much smaller Cordilleran in some regions even a bit warmer.
ice sheet over the Rockies in the American West. The In the decades since this reconstruction was pub-
Scandinavian ice sheet in northern Europe and the lished, several of its features have been challenged, and
Barents ice sheet on the northern Eurasian continen- a few of them are almost certainly wrong. Yet the
tal shelf represented about 22% of the extra ice. The CLIMAP reconstruction of the ice-age Earth is still the
remainder was accounted for by expansion of ice sheets standard against which challenges are directed.