Washington, ATMS 111

Excerpt: ... By Alexa Fiander and Sarah Coffman Greenland Photograph taken from space of the southern part of the Greenland Ice sheet. The photo reveals the full land covering during the winter months. Notes- Background Information The Greenland Ice sheets are body of ice covering about 1.71 million km2 (approximately 80% of the surface of Greenland). It ranges from 2-3 km in thickness, with the thinner portions along the outskirts of the sheet. The sheet consist of more than a hundred thousand years worth of layers of compressed snow. Therefore it provides some of the most valuable records of past climates The Greenland ice sheet is especially susceptible to global warming due to position by the Arctic. There is much debate about whether or not the ice sheet is melting at a substantial enough rate to have a notable effect on the environment in the near future. However, studies have revealed that the ice sheets are melting at a rate of 195 cubic km per year Sources: photo: http:/academic.emporia.edu/aberj ...

Washington, ESS 203

Excerpt: ... 998, an outburst flood came from under Donjek Glacier http:/www.eos.ubc.ca/research/glaciology/album/DonjekFlood/ Source of the flood waters The flood came out of this tunnel http:/www.eos.ubc.ca/research/glaciology/album/DonjekFlood/ The Tunnel has Collapsed The canyon walls are roughly 30 m high http:/www.eos.ubc.ca/research/glaciology/album/DonjekFlood/ The Aftermath Flood left icebergs scattered over Donjek Valley http:/www.eos.ubc.ca/research/glaciology/album/DonjekFlood/ The Missoula Floods Coming soon, in a Lab near you M. Parfit. 1995.The floods that carved the West. Smithsonian. 26(1) 48-59. The Message Water and glaciers can be a dangerous combination Ice-Age World What was it like ? How did it end ? At 20 ka BP, Earth was in the grip of an ice age Thick glacial ice sheets covered large areas. The ice sheets needed a combination of moisture and cold temperatures to form and survive. Laurentide Ice Sheet (North America) Fennoscandian Ice Sheet (Sca ...

Washington, ATMS 111

Excerpt: ... The Greenland Ice Sheet George Gruber Kathleen Flannigan The Greenland Ice Sheet Covers 500,000 sq. km of Greenland (approximately 85% of the island). As thick as 2km, As large as France and Spain combined. The ice has pushed the island's center 300 ...

Washington, ATMOS 111

Excerpt: ... came toward the coast, where the ice speeds up as the flow narrows into a few outlet glaciers that deliver the ice to the sea. Those glaciers moved only 9% faster than normal in August of 2006. "Meltwater does indeed cause substantial speedup" inland on the ice sheet, says Joughin, "but it has a small effect on outlet glaciers." That may be because the beds on which outlet glaciers slide are already smooth and well lubricated yearround, the group speculates. All in all, meltwater lubrication "likely will have a substantive but not catastrophic effect on the Greenland Ice Sheet's future evolution," the group writes. Alley agrees. "Could things go two times faster [due to meltwater] than we thought 10 years ago?" he asks. "Yes. They can go faster but not ridiculously faster." The danger now, warns glaciologist Robert Bindschadler of GSFC, is "falling into the same `We now know how ice sheets work'trap that my generation was guilty of 5 years ago." After all, some of Greenland's outlet glaciers began galloping t ...

Washington, OCEAN 450

Excerpt: ... rom the melting of the Greenland ice sheet. 15 Last Glacial Maximum (~20K yrs ago) and afterwards What was climate like during LGM? What happened to end LGM? How has climate varied since LGM? What were the likely mechanisms of climate change? 16 Ice Sheet Extent Laurentide, Cordilleran and Scandinavian Ice Sheets Areal extent at LGM reconstructed by 14C dated end moraines (25% of land covered at LGM vs 10% today). Thickness of ice sheets is harder to estimate than area. 17 Repeating Series of Glacial Conditions Punctuated with Interglacial Events 18 Solar Insolation Solar insolation during the LGM was about the same as today. 19 Sea Level at Last Glacial Maximum Sea Level was lower than today by ~125m based on depth of submerged corals that lived ~20K yrs (14C or U/Th dated); Large areas of continental shelves (~7% of earth) are exposed by the LOWER Sea Level; Ocean was more saline (by ~1 ppt); 18O of seawater enriched (higher) by ~1.1 ...

Colorado, GEOL 3950

Excerpt: ... d trace amounts of other gases such as CO2) CO2 has increased 1-3 ppm every year since 1958 and currently this year it is 378 ppm. CO2 in the past 100,000 years can be determined from air bubbles preserved in glacial ice cores drilled in the Greenland and Antarctic ice sheets . The cores indicate that CO2 was 280 ppm before the industrial revolution (1800- fig 4) and has been increasing every year since that time as more and more coal and oil are burned for fuel and more and more forests are cut and burned to create agricultural land. During the last glaciation, when the average temp of the earth was 8C (fig 2), CO2 was even lower, approximately 180 ppm . (fig 5) Low CO2 during the last glaciation might have resulted from a lack of oceanic deep water circulation and storage of CO2 in deep ocean sediments. The concentration of CO2 in the atmosphere during the Cretaceous was much, and the earth average temp much warmer than today, approximately 25C (fig 4 in lec #20) A summary of the CO2 in the atmospher ...

Wisconsin, AMRC 2008

Excerpt: ... past whether such collapses ever happened. The aim of this work is to study the interactions between climate and ice sheets , especially the Antarctic ice sheet. I have developed a coupling method between an antarctic ice sheet model and a climate model of intermediate complexity, which was first coupled with a northern hemisphere ice sheet model. In the first part, I have tested this new tool to understand processes occurring during the last major collapse of northern and southern ice sheets (i.e. the last deglaciation, 21 kyr BP). The ice sheets seem sensitive to the climate forcing (insolation and CO2) and respond also to the climatic variability induced by ice melting itself. The Quaternary period is one of the rare period in the Earth history where such ice sheets were present. Studying the interactions of these ice sheets with the climate is therefore an important challenge, both for past and future climate investigations. ...

San Jose State, MET 112

Excerpt: ... Lecture 10 Notes Dansgaard-Oeschger Oscillations In a previous lecture, we discussed climate changes apparently caused by the socalled "Milankovitch Cycles", i.e., variations in the Earth's rotational and orbital motions. Although rapid compared to ...

Alaska Anch, GEOL 310

Excerpt: ... REVIEW ARTICLE The role of subglacial water in ice-sheet mass balance In the coming decades, signicant changes in the polar regions will increase the contribution of ice sheets to global sea-level rise. Under the ice streams and outlet glaciers that deliver ice to the oceans, water and deformable wet sediments lubricate the base, facilitating fast ice ow. The inuence of subglacial water on fast ice ow depends on the geometry and capacity of the subglacial hydrologic system: water moving rapidly through a well-connected system of conduits or channels will have little impact on ice-sheet velocities, but water injected into a spatially dispersed subglacial system may reduce the effective pressure at the base of the ice sheet, and thereby trigger increased ice-sheet velocities. In Greenland, the form of the subglacial hydrologic system encountered by increasing surface melt water will determine the inuence of changing atmospheric conditions on ice-sheet mass balance. In Antarctica, subglacial lake ...

Penn State, EARTH 002

Excerpt: ... Earth 2 Thursday, February 11th, 1999 Announcements: Test is on Tuesday! Lecture notes: CRYOSPHERE The cryosphere consists of the vast amount of seawater on earth 98% Seawater 2% Frozen SNOW The snow cover has the mopst rapid response time It has an albedo greater than .80 This is the ice-albedo feedback: Snow Accumulation->Transformations. SNOW->AIR.LOSS->ICE->FABRIC->DEFORM->FLOW Air is lost in between grains of snow, creating a firn Snow becomes a group of equi-anuglar crystals ICE SHEET The ice cap is actually flowing, deforming, and flowing toward the ocean Ice Sheets 1)Record climate change 2)Show sea level rise/decline PERMAFROST Permafrost consists of permanantly frozen soil Contains lots of methane SEA Temperature cools->denser, lighter water as it nears freezing point Ocean doesn't reach this lightening point until it's a little cooler than freezing Less dense water on top of the ocean is what cretaes sea ice Sea ice only covers 10% of the oceans in the Northern Hemisphere Se ...

Virginia Tech, GEOS 1014

Excerpt: ... The History of Earth and Life Lecture 41 1 Lecture 41 - The Pleistocene Ice Ages Mountain Glaciers Ice builds up in the area where more snow falls than ice melts Gravity pulls the ice downhill, just as it would any material, and the glacier ends where melting is as fast as ice flow into the area Glacial ice under pressure flows around all loose material, rocks or soil, on the surface and moves it with the flow of the ice At the end of the glacier this material accumulates as the end moraine When the glacier melts back (shrinks), it leaves the material it was carrying as ground moraine Erosion by mountain glaciers sculptures the land into distinctive forms We can see evidence of the erosion of mountain glaciers after they have melted away in the landforms left by glacial erosion: cirques, U-shaped valleys, kettles (ponds), etc. Continental Ice Sheets Large ice-sheets build up on the land surface in very cold climates The ice becomes very thick (over two miles thick in the ...

Washington, OCEAN 450

Excerpt: ... rom 5 to 3 Ma ago was warmer than today. High-latitude sea surface temperatures were up to 7C higher, no Greenland ice cap, and the sea level was about 10 to 20 m higher than today. Hence, it represents a possible future climate scenario predicted by numerical models. The last 3 million years show alternating glacial and interglacial climate stages, while glacial ice sheets reached their largest size during the last 700,000 years. During the Pliocene, global temperatures, particularly at high latitudes, are believed to have been significantly warmer than today. Above figure shows the Pliocene surface air temperature increase compared to the present day simulated by the NASA/GISS global climate model. Values are in C. This is how global warming was distributed in the Pliocene Pliocene sea surface temperatures. Differences from modern values values for two selected months. Units are C. The Pliocene was the time when our ancestors developed (5 to 1.8 My) And was the beginning of the `modern' glacial/int ...