DEFINITION OF ICE CAP

Definition of ice cap

Glaciers are any permanent body of ice (recrystallized

snow) that shows evidence of gravitational movement.

Ice caps form dome-shaped bodies of ice and snow over

mountains and flow radially outward. They cover high peaks

of some mountain ranges, such as parts of the Kenai and

Chugach Mountains in Alaska, the Andes, and many in the

Alpine-Himalayan system. Ice caps are relatively small, less

than 20,000 miles (50,000 km2), whereas ice sheets are similar

but larger. Ice sheets are huge, continent-sized masses of

ice that presently cover Greenland and Antarctica. Ice sheets

contain about 95 percent of all the glacier ice on the planet. If

global warming were to continue to melt the ice sheets, sea

level would rise by 230 feet (70 m). A polar ice sheet covers

Antarctica, consisting of two parts that meet along the

Transantarctic Mountains. It shows ice shelves, which are

thick glacial ice that floats on the sea. By calving these form

many icebergs, which move northward into shipping lanes of

the Southern Hemisphere.

Global sea levels are currently rising, partly as a result of

the melting of the Greenland and Antarctica ice sheets. We

are presently in an interglacial stage of an ice age, and sea

levels have risen nearly 400 feet (120 m) since the last glacial

maximum 20,000 years ago, and about six inches (15 cm) in

the past 100 years. The rate of sea-level rise seems to be

accelerating and may presently be as much as a centimeter

every five years. If all the ice on both ice sheets were to melt,

global sea levels would rise by another 230 feet (70 m), inundating

most of the world’s major cities, and submerging large

parts of the continents under shallow seas. The coastal

regions of the world are densely populated and are experiencing

rapid population growth. Approximately 100 million

people presently live within 3.2 feet (1 m) of the present-day

sea level. If the sea level were to rise rapidly and significantly,

the world would experience an economic and social disaster

on a magnitude not yet experienced by the civilized world.

Many areas would become permanently flooded or subject to

inundation by storms, beach erosion would be accelerated,

and water tables would rise.

The Greenland and Antarctic ice sheets have some significant

differences that cause them to respond differently to

changes in air and water temperatures. The Antarctic ice

sheet is about 10 times as large as the Greenland ice sheet,

and since it sits on the south pole, Antarctica dominates its

own climate. The surrounding ocean is cold even during summer,

and much of Antarctica is a cold desert with low precipitation

rates and high evaporation potential. Most meltwater

in Antarctica seeps into underlying snow and simply

refreezes, with little running off into the sea. Antarctica hosts

several large ice shelves fed by glaciers moving at rates of up

to a thousand feet per year. Most ice loss in Antarctica is

accomplished through calving and basal melting of the ice

shelves, at rates of 10–15 inches (25–38 cm) per year.

In contrast, Greenland’s climate is influenced by warm

North Atlantic currents, and by its proximity to other landmasses.

Climate data measured from ice cores taken from the

top of the Greenland ice cap show that temperatures have

varied significantly in cycles of years to decades. Greenland

also experiences significant summer melting, abundant snowfall,

has few ice shelves, and its glaciers move quickly at rates

of up to miles per year. These fast-moving glaciers are able to

drain a large amount of ice from Greenland in relatively short

amounts of time.

The Greenland ice sheet is thinning rapidly along its

edges, losing an average of 15–20 feet (4.5–6 m) in the past

decade. In addition, tidewater glaciers and the small ice shelves

in Greenland are melting at an order of magnitude faster than

the Antarctic ice sheets, with rates of melting around 25–65

feet (7–20 m) per year. About half of the ice lost from Greenland

is through surface melting that runs off into the sea. The

other half of ice loss is through calving of outlet glaciers and

melting along the tidewater glaciers and ice shelf bases.

These differences between the Greenland and Antarctic

ice sheets lead them to play different roles in global sea-level

rise. Greenland contributes more to the rapid short-term fluctuations

in sea level, responding to short-term changes in climate.

In contrast, most of the world’s water available for

raising sea level is locked up in the slowly changing Antarctic

ice sheet. Antarctica contributes more to the gradual, longterm

sea-level rise.

See also GLACIER.

Title Post:
Rating: 100% based on 99998 ratings. 99 user reviews.
Author:

Terimakasih sudah berkunjung di blog SELAPUTS, Jika ada kritik dan saran silahkan tinggalkan komentar