Astronaut Photography - Observing Earth's Systems from Space
by Rebecca Dodge in collaboration with NASA scientists
Repeat observations are needed of many parts of earth system, so that scientists and planners can monitor, model, and predict cyclic and long-term climate change, as well as anthropogenic change. Glaciers are particularly sensitive to long-term climate change; ongoing global melting and retreat have placed glacier monitoring on the list of Crew Earth Observation targets. Glaciers in the Patagonian icefields of South America number in the hundreds and most have been in retreat since the 1960s; some have retreated over 4 km34. Upsala Glacier in Chile, shown in the photograph to the left33, has retreated noticeably since the launch of the ISS and the start of the Crew Earth Observations Program, as have other Patagonian glaciers35. The Crew Earth Observations program photographs these glaciers repeatedly to provide monitoring data for scientists studying climate change.
Repeated observations are critical because local climate variability can cause short-term retreat or advance unrelated to global warming. Only long-term observations of glaciers around the globe can provide useful data for research concerning global warming and its possible causes36 (including natural fluctuations within the Earth System as well as human activities). Many glaciers are located in extremely remote and inaccessible regions. Satellite-based observations are critical to the monitoring process.
34. (http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=16441 Glacial Retreat)
35. (http://eol.jsc.nasa.gov/EarthObservatory/Glacial_Retreat_in_Chilean_Patagonia.htm Glacial Retreat in Chilean Patagonia)
36. (http://earthobservatory.nasa.gov/Study/Glaciers/ At the Edge: Monitoring Glaciers to Watch Global Change)
Glacial retreat is another type of event whose effects resonate across Earth's Systems. Glaciers are sustained (neither advancing nor retreating) by climatic conditions that favor a balance between accumulation of snow during the winter and melting processes as the seasonal weather warms. Climate change that reduces snowfall, increases melting or a combination of these two will result in glacial retreat.
Increased melting releases freshwater into the Hydrosphere including lakes, streams and the oceans37. Flooding can become a problem when lakes and streams cannot hold the excessive runoff. Once glaciers have melted, communities that rely on glacial meltwater for agriculture will have no alternative water resources. Communities around the world are already facing this challenge. Increased melting and runoff ends up in the oceans, where sea level rise is the obvious consequence. Rising sea level will challenge countries around the world, flooding coastal cities and farmlands, displacing humans and destroying entire natural ecosystems (Biosphere).
37. (http://earthobservatory.nasa.gov/Study/GLIMS/ Sizing up the world's glaciers)
Glacial melting can directly impact climates locally, regionally, and globally38. Increased fresh water runoff from Arctic glaciers may have the effect of creating more Arctic and sea ice, which has high albedo properties; increased reflectance would lower Atmospheric temperatures in the North Atlantic. Sea ice also prevents sea water from exchanging heat with the atmosphere, reinforcing the cooling effects of increased reflectance. The local effects of large bodies of glacial ice create a persistent high pressure system, drying local climates. New local climate conditions may require new agricultural practices, concurrent with the loss of water resources enforced by glacial retreat.
38. (http://earthobservatory.nasa.gov/Study/PolarParadox/ Polar Paradox)
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