Summer Scarlatelli
Ice Sheets and the Hydrosphere
1.) Hydrologic Cycle
H>E>A
The hydrologic cycle, also called the water cycle is a model that describes the movement and
storage of water between Earth’s four spheres. On Earth, water can be stored in any of the
following reservoirs: atmosphere (water vapor), oceans, lakes, streams, rivers, groundwater,
soil, snowfields and ice sheets (glaciers and icebergs). Earth’s water can be continuously cycled
through threes reservoirs through process like condensation, precipitation, evaporation,
sublimation, transpiration, infiltration, groundwater flow and melting. According to
www.physicalgeography.net, 2.05 percent of Earth’s water is stored in ice caps and glaciers and
water lasts in glaciers for 20 to 100 years.
Table 8a: Hydrologic Cycle
Table 8b-1: Inventory of water at the Earth's surface.
Reservoir
Oceans
Ice Caps and Glaciers
Volume (cubic km x 1,000,000) Percent of Total
1370
97.25
29
2.05
Groundwater
9.5
0.68
Lakes
0.125
0.01
Soil Moisture
0.065
0.005
Atmosphere
0.013
0.001
Streams and Rivers
0.0017
0.0001
Biosphere
0.0006
0.00004
Table 8b-2: Typical residence times of water found in various reservoirs.
Reservoir
Glaciers
Seasonal Snow Cover
Soil Moisture
Groundwater: Shallow
Groundwater: Deep
Lakes
Rivers
Average Residence Time
20 to 100 years
2 to 6 months
1 to 2 months
100 to 200 years
10,000 years
50 to 100 years
2 to 6 months
References:
http://www.physicalgeography.net/fundamentals/8b.html
http://earthobservatory.nasa.gov/Features/Water/water_2.php
2.) Rise in Sea Level
E>H
Each year in the Arctic in the beginning of summer, the ice cap covering the North Pole, start to
recede and regenerate at the onset of winter. According to Ocean Conservancy scientists have
been measuring the ice caps in the middle of the summer since 1979. “In 2005 the extent of
sea-ice was 20% lower than 1979—a troubling trend, to be sure. Just two years later, in 2007,
the cap receded to a level 43% lower than the 1979 measurement—a rate that startled
everyone, including scientists. If this trend continues, the North Pole could be entirely devoid of
summer sea ice by 2050”. The natural expansion of seawater as it warms and the melting of
land-based ice is causing global sea levels to rise. According to Roach (2006), sea levels globally
have risen an estimated 0.1 inch a year over the past decade. Many scientists fell that it is
possible for global sea levels would rise and estimated 20 -21 feet if all of the ice on Greenland
were to melt into the North Atlantic Ocean. Greenpeace organization estimates that the
Antarctic ice sheet holds enough frozen water ( 60% of Earth’s freshwater is stored in these
sheets) to make sea levels rise 203 feet.
References:
Roach, J. (2006). Greenland Ice Sheet Is Melting Faster, Study Says. National Geographic News.
Retrieved from: http://news.nationalgeographic.com/news/2006/08/060810-greenland.html
(2006). Study Previews Ice Sheet Melting, Rapid Climate Change. Retrieved from:
http://www.sciencedaily.com/releases/2006/03/060312210108.htm
(2004) A Chilling Possibility. Retrieved from:
http://science.nasa.gov/headlines/y2004/05mar_arctic.htm
http://www.greenpeace.org/international/campaigns/oceans/globalwarmingoceans
http://pubs.usgs.gov/fs/fs2-00/
http://www.theglobaleducationproject.org/earth/global-ecology.php
http://www.oceanconservancy.org/site/News2?page=NewsArticle&id=10341
http://earthobservatory.nasa.gov/Features/Water/water_2.php
http://www.oceanconservancy.org/site/News2?page=NewsArticle&id=10341
3.) Ocean Currents
E>H
The water in our world's oceans is constantly moving wether it is pushed and pulled by tides or
blown by waves. Through the force of the Great Ocean Conveyor Belt (also called the
thermohaline circulation) the ocean is gradually circulating around the globe. One of the most
well known parts of the Great Ocean Conveyor is the Gulf Stream which helps give Europe a
somewhat moderate climate. It is powered by distinctions in water temperature and salinity
and the melting of a large part of the Arctic ice could switch off, slow down or divert the Great
Ocean Conveyor. Australian scientists feel that the ice could release too much fresh water and
could get in the way with the formation of dense "bottom water," which sinks 4-5 kilometers to
the ocean floor. A slowdown in the system known as "overturning circulation" (2009) could
have a great affect on the way the ocean carries heat around the globe. Unfortunately if the
ocean water salinity drops too low than the Great Ocean Conveyor will not be able to make
water cold and salty enough to sink. This cold and dense water is formed in polar regions by
surface water freezing, which accumulates salt in very cold water beneath the ice and then
sinks. “Only a few places around Antarctica and in the northern Atlantic create water dense
enough to sink to the ocean floor, making Antarctic "bottom water" crucial to global ocean
currents”.
The global oceanic conveyer belt, is a unifying concept that connects the ocean's surface and
thermohaline (deep mass) circulation regimes, transporting heat and salt on a planetary scale.
References:
Byrnes, M. (2009).Southern Ocean current faces slowdown threat. Retrieved from :
http://www.asoc.org/Portals/0/pdfs/Southern%20Ocean%20current%20faces%20slowdown%2
0threat.pdf
http://www.greenpeace.org/international/campaigns/oceans/globalwarmingoceans
http://www.theglobaleducationproject.org/earth/global-ecology.php
4.) Ice Formation
H>E
The cryosphere is composed of all of the frozen water found in the hydrosphere. The two
components that comprise it are the continental or land ice and sea ice. Continental ice can
be found mainly in Greenland and Antarctica however you can also find smaller ones in China
and South America. Valley glaciers which are part of continental ice can actually be found on
every continent except Australia.
Continental ice forms when snow accumulates on the surface of land and over time
compresses under the weight of snow on the surface. Snow accumulates during the winter
from precipitation and accumulates from the weight of the new snow. As the snow melts,
water filters into the snow and fill in the available air space and freezes at the snow-ice
boundary. The continental ice formation and flow process is generally very slow and the build
up or decay of ice sheets like valley glaciers can take decades or centuries. Sea ice includes
frozen water from the ocean, rivers and lakes. It is formed by the direct freezing of the water, if
the water is salty when it freezes the salt is left in the water and leaves the rest of the water
around it denser and with a higher salinity. River and lake ice is frozen mainly from fresh water
generally and is therefore is not salty.
References:
Schiele, E. (2009). Melting Ice Sheets Impact. Retrieved from:
http://www.bbc.co.uk/climate/impact/glaciers.shtml
http://earth.rice.edu/mtpe/cryo/cryosphere.html
5.) Earthquakes
E>H>L
As ice sheets melt, they can release pent-up energy and trigger massive earthquakes, according
to new study. Roughly 10,000 years ago a series of large earthquakes shook Scandinavia along
fault lines that are now quiet. Each earthquake occurred in roughly the same time period of the
melting of the thick ice sheets from the last ice age. Scientists think that the melting of the ice
sheets triggered the earthquakes by releasing the pressure that had been building up on Earth’s
crust, and triggered these earthquakes by releasing pressure that had built up in Earth's crust.
References:
Inman, M. (2008). Melting Ice Sheets Can Cause Earthquakes, Study Finds. National Geographic
News. Retrieved from: http://news.nationalgeographic.com/news/2008/03/080314-warmingquakes.html
6.) Ice Sheet Slippage
E>H
Antarctica's ice sheet is sliding faster and further into the ocean when the ice sheet hit underice lakes. Ice is continually sliding off of Antarctica and into the ocean. Inland ice slip into the
ocean more than ten times faster when they hit ice streams than do the rest of the ice sheet.
Scientists have recently discovered a large under-ice lakes right at the start of a massive ice
stream in East Antarctica. This stream currently dumps 35 billion tons of ice into the sea each
year. The lakes, buried deep below the thick ice sheet that runs miles deep, providea water and
heat that lubricate the ice sheet thus creating ice streams. According to Inman, “the formation
of some subglacial lakes could ultimately lead to accelerated rates of sea-level rise."
References:
Inman, M. (2007). Buried Lakes Send Antarctica's Ice Slipping Faster Into the Sea, Study Shows.
National Geographic News. Retrieved from:
http://news.nationalgeographic.com/news/2007/02/070221-antarctica-lakes_2.html
7.) Lakes Form
E>H
Water aggregates underneath glaciers where regions of low pressure are enclosed by regions of
high pressure. Water can also accrue in a depression in the bedrock below the ice dome, in
locations such as a crater. A dome of water can form if the glacier bed is flat and the surface ice
has a central depression, thus creating a somewhat low-pressure area in the center of the ice
which then fills with water. Large reservoirs like this are known to exist under the Antarctic ice
cap, one is even estimated to be 8000 square kilometers.
References:
http://www.teachersdomain.org/resource/ipy07.sci.ess.watcyc.icesimulate/