Samstag, 25. Februar 2012

A Tour of the Cryosphere

The cryosphere consists of those parts of the Earth's surface where water is found in solid form, including areas of 
  • snow,  
  • sea ice,  
  • glaciers,  
  • permafrost,  
  • ice sheets 
  • icebergs
In these regions, surface temperatures remain below freezing for a portion of each year.

Since ice and snow exist relatively close to their melting point, they frequently change from solid to liquid and back again due to fluctuations in surface temperature
  • Although direct measurements of the cryosphere can be difficult to obtain due to the remote locations of many of these areas, using satellite observations scientists monitor changes in the global and regional climate by observing how regions of the Earth's cryosphere shrink and expand
This animation portrays fluctuations in the cryosphere through observations collected from a variety of satellite-based sensors
  • The animation begins in Antarctica, showing ice thickness ranging from 2.7 to 4.8 kilometers thick along with swaths of polar stratospheric clouds
  • In a tour of this frozen continent, the animation shows some unique features of the Antarctic landscape found nowhere else on earth
  • Ice shelves, ice streams, glaciers, and the formation of massive icebergs can be seen. 
A time series shows the movement of iceberg B15A
  • an iceberg 295 kilometers in length which broke off of the Ross Ice Shelf in 2000
Moving farther along the coastline, a time series of the Larsen ice shelf shows the collapse of over 3,200 square kilometers ice since January 2002.

As we depart from the Antarctic, we see the seasonal change of sea ice and how it nearly doubles the size of the continent during the winter.
  • From Antarctica, the animation travels over South America showing areas of permafrost over this mostly tropical continent
  • We then move further north to observe daily changes in snow cover over the North American continent
  • The clouds show winter storms moving across the United States and Canada, leaving trails of snow cover behind. 
In a close-up view of the western US, we compare the difference in land cover between two years:
  • 2003 when the region received a normal amount of snow and 2002 when little snow was accumulated
  • The difference in the surrounding vegetation due to the lack of spring melt water from the mountain snow pack is evident
As the animation moves from the western US to the Arctic region, the areas effected by permafrost are visible. 

In December, we see how the incoming solar radiation primarily heats the Southern Hemisphere
  • As time marches forward from December to June, the daily snow and sea ice recede as the incoming solar radiation moves northward to warm the Northern Hemisphere
Using satellite swaths that wrap the globe, the animation shows three types of instantaneous measurements of solar radiation observed on June 20, 2003
  • shortwave (reflected) radiation, 
  • longwave (thermal) radiation
  • net flux (showing areas of heating and cooling). 
Correlation between reflected radiation and clouds are evident.

When the animation fades to show the monthly global average net flux, we see that the polar regions serve to cool (!) the global climate by radiating solar energy back (!) into space throughout the year
  • The animation shows a one-year cycle of the monthly average Arctic sea ice concentration followed by the mean September minimum sea ice for each year from 1979 through 2004
  • A red outline indicates the mean sea ice extent for September over 22 years, from 1979 to 2002
The minimum Arctic sea ice animation clearly shows how over the last 5 years the quantity of polar ice has decreased by 10 - 14% from the 22 year average.

* * *

Keine Kommentare: