Dr. Perovich's lecture shed light on a key concept related to climate change: the loss of polar sea ice. While I have spent my fair share of time looking at images of polar bears floating atop small ice fragments, I have never understood specifically the cause of this phenomenom.

Dr. Perovich began his talk by explaining that the arctic is the ecosystem that is most at risk of being lost to climate change today. He described the phenomenom as " real time plate tectonics", because the landscape scale changes are happening so quickly. He described how 30 years of satellite images have been used to evaluate changes in the sea ice. Ice is at a minimmum in September and at a maximum in February. When the annual variations are taken out, there is clear trend of ice cover being lost in the summer and in the winter. This change amounts to a loss of 11% per decade. In 2007, ice cover was at an all time low. Between 1980 and 2008, the ice cover went from being the size of the lower 48 states to being less than half that size.

Despite the high quality data about the loss of ice, it is still difficult to determine the cause of reduced polar ice. This is due to the fact that we have poor data about the thickness of ice over time. The most reliable data is from submarines during the cold war. Using the data, it has been determined that ice is thining everywhere in the arctic with an average decrease of approximately 40% in the last 30 years from over 3 meters to less than 2 meters.

At this point, Dr. Perovich described the albedo effect. This positive feedback cycle is driven by the fact that ice and snow reflect the highest amount of sunlight back into space. In contrast, the ocean has an albedo effect of only 7% reflection, resulting in an increase in warming as the ice cover diminishes. The amount of solar input can be measured over time. It is calculated using the format:

(SUNLIGHT) X (ALBEDO) X (AREAS OF OPEN WATER)

When measured from 1982-2007, it was found that the amount of solar input has more than doubled in that time period. Using series of measuring techniques, it was determined that the recent melting has been largely in the form of bottom melting. This may be triggered by warm water coming form the Bering Sea, but it is likely due to the warming sea water from the albedo effect.

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