Climate and Global Change Notes 28-1 Climate & Global Change Ice and Sea-Level Rise Changes Melting...

Climate and Global Change Notes

28-1

Climate & Global Change

Ice and Sea-Level Rise

ChangesMeltingExpansion

Science Concepts

The Earth System (Kump, Kastin & Crane)

• Chap. 15 (pp. 313-315)• Chap. 16 (pp. 329-332)


28-2

Sea-Level Rise

Causes of Sea-Level Change

• Thermal expansion

• Addition of water, i.e., from melting glaciers

• Changes in salinity; fresh water is less dense than salt water and thus takes up slightly more space than an equal mass of salt water

• Graph of data from satellites and floats (mechanical devices drifting in the ocean), show

that sea level rose, on average, 3 mm (0.1 inches) per year between 1993 and

2005

• Researchers attributed about half of this increase to melting ice and half to

thermal expansion

http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17300

Change in mean sea level (mm)

Trend

60-Day Average

-20

-10

0

10

20

30

1994

1996

1998

2000

2002

2004


28-3

Sea-Level Rise

Causes of Sea-Level Change

Intergovernmental Panel on Climate Change, Climate Change 2001; Synthesis Report, p. 67

Terrestrial water storage,extraction of groundwater,building of reservoirs,changes in runoff andseepage into aquifers

Subsidence in river delta region,

land movements andtechtonic movements

Surface and deep ocean circulation changes and

storm surges

Expansion of water caused by warming

Exchange of the water stored on land by

glaciers and ice sheets with ocean water


28-4

Explanation

• Sea-level could rise 1-4 ft during the next 100 y due to global warming

The mechanism underlying is simple;- As ocean waters

heat, they expand

- Water locked up in small landed glaciersmelt

The Greenland and West Antarctic ice sheets each contain enough water

to raise sea level about 22 ft, while East Antarctica has enough ice to

raise sea level over 190 ft.

Sea-Level Rise

http://www.cresis.ku.edu/research/data/sea_level_rise/h_southeast-usa.html


28-5

Changes in Glacial and Sea Ice

Glaciers

• IKONOS satellite image Bear Glacier along the Gulf of Alaska on 8/8/05- IKONOS comes from the Greek

word for "image"- IKONOS is a commercial

multispectral Earth observation satellite that collects imagery at 1- and 4-m resolution

• Note- Small icebergs floating in lake- Crevasse region- Dark gray “racing stripes” are dirt

and debris from rocks glacier passes - Bright blue-green color of small lake

result of “glacial flour” - highly reflective fine sediment ground off rocks by the ice and carried down slope



28-6


Glaciers Around the World - Montana & Washington

• “More than 110 glaciers have disappeared from Montana’s Glacier National Park over the past 150 years, and researchers estimate that the park’s remaining 37 glaciers may be gone in another 25 years.”- Example to right: Sperry Glacier retreated 15-22

m/y from 1913-1945; then retreated at 11 m/y to about 5 m /y from 1950-1979; from 1979-1993 retreated from 3-5 m/y

• South Cascade Glacier in the Washington Cascade Mountains (below) retreat from 1928, 1979, and 2000

http://www.nrmsc.usgs.gov/research/glacier_retreat.htm

http://earthobservatory.nasa.gov/

Study/GLIMS/


28-7

Glaciers Around the World - Africa

• “Half a world away on the African equator, Hemingway’s snows of Kilimanjaro are steadily melting and could completely disappear in the next 20 years.”

Observation -

Ice on Africa's highest mountain

shrank by 80% in the past century. The snow cap formed some 11,000

years ago.

Landsat captured these images of Kilimanjaro

2/17/93 (top) and 2/21/00 (bottom).


QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.



http://www.giss.nasa.gov/research/news/20031222/

http://earthobservatory.nasa.gov/Study/GLIMS/


28-8


Glaciers Around the World - Alps

• “And in the Alps, glaciers are retreating and disappearing every year … .”

• Composite ASTER image of Gangotri Glacier

(Himalayas) terminus - Contour lines are

approximate

http://earthobservatory.nasa.gov/Study/GLIMS/Image by Jesse Allen, Earth Observatory; Based on data from the ASTER Science Team; Glacier retreat boundaries from the Land Processes Distributed Active Archive Center



Observation -

Retreating glaciers may cause some earthquakes. Study of glaciers in several parts of the world suggests that the number of earthquakes have increased as large glaciers have melted.

Bull. Amer. Meteor. Soc., 2004, p.1645


28-9


Glaciers Around the World - South American Glaciers• South America’s Patagonian ice

fields and glaciers located in the far

southern Andes mountains in Argentina

• Upsala Glacier

- Third largest glacier of the

Southern Patagonian Ice Field

- Estimated area of over 800

square kilometershttp://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=16441



Yellow lineJan 2001

Yellow lineJan 2001

Jan 2004

Jan 2001


28-10Changes in Glacial and Sea

IceGlaciers Around the World - South American Glaciers (Con’t)• Upsala Glacier (Con’t)

- Glacial frontal margins

> R indicates a bare-rock

ridge [extent shown by

dark grey]

> ch indicates a water channel

> i indicates an island

[shown by light grey]



19681981

1986

1990

1993

1995

1994

http://pubs.usgs.gov/prof/p1386i/chile-arg/wet/historic.html

4 km


28-11

Glaciers Around the World - Greenland Ice Sheet

• Airborne laser used to survey the altitude of the ice sheet's surface

• 1993 and 1994

• 1998 and 1999

• Produced difference map

• Ice sheet lost at least 51 cubic kilometers of volume during that five year period


http://svs.gsfc.nasa.gov/imagewall/greenland.html



IceGlaciers Around the World - Jakobshavn Isbrae Glacier in Greenland

• Fastest moving glacier in the world

• In recent years, it has gotten even faster

• Starting in late 2000, following a period of slowing down in the mid 1990s, the glacier accelerated and its speed nearly doubled

• Each year glacier’s front edge retreated farther inland, and the colored lines on the image above mark the location of the terminus from 2001 through 2004 http://earthobservatory.nasa.gov/Newsroom/

NewImages/images.php3?img_id=16760



IceSea Ice Around the World - Antarctic Temperature Trend 1982-2004

• Strongest cooling at the South Pole, strongest warming along the Antarctic Peninsula

• Bright red spots or streaks along edge of continent show where icebergs calved or ice shelves disintegrated, meaning satellite began seeing warmer ocean water

• One possible cause involves ozone in the stratosphere that absorbs UV radiation, absorbing this energy warms the stratosphere. Loss of UV-absorbing

ozone may have cooled the stratosphere and strengthened the polar vortex

around the South Pole



http://earthobservatory.nasa.gov/

Newsroom/NewImages/images.php3?img_id=17257



IceSea Ice Around the World - Antarctica

• Image from SyntheticAperture Radar (SAR) on the Canadian RADARSAT satellite.SAR has 100 m resolution thatcan sense Earth's surface indarkness or through clouds

• 10/13/98 ice more than 90 mileslong and almost 30 miles widebroke away or “calved” fromRonne Ice Shelf in Antarctica

http://science.nasa.gov/headlines/y2000/ast27dec_1.htm



IceSea Ice Around the World - Antarctica (Con’t)

• Moderate Resolution Imaging Spectroradiometer (MODIS) on the NASA Earth Observing System (EOS) Terra satellite

• Larsen B ice shelf inAntarctica disintegratedin 35-day period

Shattered ice formed a"plume" of thousands oficebergs now adrift inthe Weddell Sea

http://www.nsidc.org/iceshelves/larsenb2002/index.html



Ice

Sea Ice Around the World - Antarctica (Con’t)

• Retreat of the ice shelves on theAntarctic Peninsula

1986 1997Antarctica

Larsen Ice Shelf area (km2)

0

5000

10000

15000

1986 1990 1994 1998

RADARSAT

100 km 100 km



IceSea Ice Around the World - Arctic

• Changes between 1958-1976 average and 1993-1997 average

http://www.grida.no/climate/vital/30.htm


28-18

Ocean Currents

Sea Ice Around th e World - Arctic (Con’t)

• 2007 sets record Arctic sea ice melt

• Sept. 16, 2007, sea ice extent was 4.13 million km2 (1.59 million miles2)

• 38% below average and 24% below 2005 record

• 2007 brought an ice-free opening though Northwest Passage for several weeks

Alaska Canada



28-19

Ocean Currents

Sea Ice Around the World - Arctic (Con’t)

• Graph of sea ice melt shows the 5-day mean sea ice extent for June through Sept.

• Sea ice acts as the Earth’s built-in air conditioner - its light color reflects most sunlight

• In contrast, dark ocean water absorbs most of sunlight

• As sea ice continues melting, increased exposure of ocean water changes

Earth’s; thus, contributing to further warming thereby leading to continued

sea ice melt and reinforcing the melting cycle

• As summer melt continues to increase, wintertime recovery becomes more

difficult to achieve



28-20

Ocean Currents

Sea Ice Around the World - Arctic (Con’t)

• July Arctic perennial sea ice has been decreasing at a rate of 6% per decade since 1979

• Images show the minimum sea ice concentration in 1979 and 2003

- Data were collected by the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imager (SSMI). Credit: NASA

http://www.gsfc.nasa.gov/topstory/2003/1023esuice.html





1979

2003http://earthobservatory.nasa.gov/Study/ArcticReflector/arctic_reflector2.html


28-21

Facts

• Sea ice also thinned by about 40% in recent decades, from an average of

10 ft in the period 1958-1976 to about 6 ft in the period 1993-1997. On

average, current thinning is estimated at about 4 in / yr.

• Since 1993, the Greenland Ice Sheet - the Arctic’s largest - has thinned by

more than a yard a year on its southern and eastern edges.

• Alaskan permafrost is thawing across the state. Near Barrow, permafrost

was 8 to 10 in thinner in 1997-1998 than it was between 1964 and

1968.

Woodard, C., 2000: The great melt: Is it normal, or the result of global warming. The Chronicle of Higher Education, July 14, XLVI, No. 45, A20-A21.


Climate and Global Change Notes 28-1 Climate & Global Change Ice and Sea-Level Rise Changes Melting...

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