Summary : Dr. Konrad Steffen discussed the remote sensing history of the Greenland ice sheet specifically addressing the applications of passive microwave and scatterometer studies. He briefly reviewed the passive microwave sensor parameters for cryosphere studies. He then discussed the results of the 17 years of data collection and their significance to climate studies. Finally his talk summarized the scatterometer studies of the Greenland ice sheet. He reviewed several active microwave applications, which further our understanding of ice dynamics in Greenland.
Significance of Cryosphere:
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Ice sheets 600 times the volume of sea ice.
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Differences between Greenland & Antarctic ice sheets
Passive Microwave Sensor parameters
Sensor Issues:
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Emissivity * Temp= brightness
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Ice depth is function of emissivity
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Dielectrical factor indicates wet vs dry snow
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Cross polarized gradient ratio allows us to get rid of temperature and access emissivity.
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Atmospheric extinction: is present ib 19 GHz band but more of a problem in 37
GHz due to the presence of summer clouds
Measurements & applications:
Passive microwave records the extent of snow melt but not the intensity. The results match well with surface temperature measurements. Mt Pinatubo isolation effect is clearly represented in their data underscoring the effect of volcanic forcing on climate.
16% increase in melt area from 1979-2002 reflecting change in climate and NAO.

Why does any of this matter?
A 3 degree temperature increase will create a vertical movement of 80 km due to the low slope of Greenland. This creates 24 terrawatts of energy added to the earth system due to a change in albedo.
Elevation of Greenland ice sheet
Lidar flight lines show areas of no change, increase and lowering. There are four outlets in Greenland where melt water can escape however these are undersea level thus water pools and accelerates melting.
Scatterometer data
Scatterometers are active microwave systems using backscatter created by dry snow as a target signal.
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Ice layer = rougher surface thus stronger return
Using this data, you are looking at the effect of wet snow, which can refreeze in ice layers making the surface rougher. A rougher surface increases the backscatter.
Scatterometer sensors measure melt more accurately than passive microwave sensors because scatterometers can identify a single melt event while passive microwave sensors require a certain amount of water to be present thus passive microwave measurements are always conservative.
There area several applications of this kind of data:

These studies monitor the changes in melt extent and snow accumulation.
Other temporal studies can capture the areas subject to change. These show the change in dry snow coverage resulting from summer melting.
Other scatterometers studies can capture snow accumulation data.

However surface height differences do not necessarily indicate changes in snow accumulation. Ice layers are denser then snow thus surface height data can identify the presence of melt layers. Melt layer events change the backscatter returns. In this graph, the sharp increase in these backscatter measurements result a melt layer formation cover by fresh snow.