Arctic sea ice extent is now more than two million square kilometers less than it was in the late twentieth century, a new scientific study published in the journal Nature shows.
Climate change is thought to be occurring faster in the Arctic than anywhere else on Earth and sea ice is considered one of the main indicators. The ice is crucial in northern ecosystems because it provides habitat for everything from plankton to polar bears.
The study, which gives the most detailed picture ever of the northern oceans over the previous millennium-and-a-half, also concludes the current decline has already lasted longer than any previous one in that period. The scientists combined 69 different data sources – tree rings, ice cores from glaciers and lake and ocean sediments. To check the validity of their approach, scientists compared their calculations for the last couple of centuries with real-world observations from satellites, ship logs and other historical accounts.
They found that by the mid-1990s sea ice had fallen even further than in previous lows such as the so-called Medieval Warm Period between 800 and 1300.
What has really dominated the changes that we see in the Arctic Ocean in the last 50 years is the rise in air temperatures and the rise in temperatures of the waters below. What makes recent sea ice declines unique is that they have been driven by multiple factors that never all coincided in historical periods of major sea ice loss, according to the report.