Satellites and Submarines Examining Arctic Sea Ice Thickness
02.09.2009 - Water & Oceans, Ice & Snow, Flora & Fauna, Human Dimension, Other, Arctic
This past summer, a group of students, accompanied by a Canadian senator, a writer, and a filmmaker joined scientists at Resoulte Bay on the icebreaker Louis S. St-Laurent on their journey to the Northwest Passage to get a firsthand look at the sea ice during a workshop designed to increase awareness of what is happening to the Arctic sea ice among non-scientists.
Parcticipating in the cruise was Ron Kwok of NASA's Jet Propulsion Laboratory, who, along with Drew Rothrock of the University of Washington, used a combination of spatial coverage from satellites with records from Cold War submarines going back 50 years in an attempt to look at sea ice thickness over the past several decades. Kwok and Rothrock's study, published in Geophysical Research Letters, paint a picture of dramatic long-term change in the Arctic: since reaching a peak in 1980, sea ice thickness has declined by 53% and multiyear permanent sea ice has thinned by more than 40% since 2004 - quite significant as thick older ice seems to be being replaced by thin seasonal ice.
The team used a number of data sources. Since the second half of the 20th century, satellites, ships, and ice charts collected by multiple countries from as far back as the beginning of the Cold War have made records quite comprehensive. Looking at past records of sea ice extent has allowed researchers to look at changes in the overall sea ice extent over time. And submarines also took sonar pictures of the underside of the sea ice during the Cold War, giving a general idea of sea ice thickness over the past half century or so. Kwok and Rothrock also used the ICESat satellite in their study to measure sea ice thickness by measuring the sea ice's height above the water (accounting for snow fall as well), calculating the ice's density and using Archimedes' Principle to calculate the volume of ice below the water.
While an extreme freeze or melt might occur in a given year due to any number of variations, the long-term trends determine the shape of the overall climate of the Arctic. Understanding these long-term trends is key in understanding how these changes will affect ecosystems and the livlihoods of Arctic residents, which is why it is important for non-scientists to understand what is happening to the ice.
Dr. Kwok was pleased to have non-scientists have a firsthand look at what is happening in the Arctic through the workshop. "Sea ice is about more than just hard science; it's a geopolitical and human issue," he said. "There is a big personal impact when you get away from your desk and see it in person."
