Arctic Sea Ice and Climate Stability

The Arctic is an integral component of the global climate system. Its vast, reflective frozen surfaces, including sea ice, ice sheets, and land-based snow, play a critical role in regulating Earth’s climate. For centuries, Arctic summer sea ice has been a lynchpin keeping the Arctic frozen.

The Arctic Ocean is covered by sea ice during the winter when the Arctic is mostly dark. As winter transitions to summer, conditions shift from near-constant darkness to near-constant sunlight. For most of human history, some of the winter sea ice would naturally melt, but most would persist. In high summer, with the sun shining on the Arctic 24 hours a day, the ice’s bright surface reflected most of this huge amount of incoming heat energy back out to space, keeping the Arctic mostly frozen in summer.

This historic dynamic has been dramatically disrupted by anthropogenic climate change. Increases in air and sea temperature in the Arctic have led to a 50 percent decline in the spatial extent of summer sea ice over the last four decades and sea ice has also lost its mass: thicker multi-year sea ice (at least five years old) has decreased by 90 percent . This drives further loss because thicker ice has a higher albedo (reflectivity) than thinner, newer ice and is also less vulnerable to seasonal melting.

As summer sea ice shrinks, an increasing amount of heat energy is absorbed by the darker ocean, rather than being reflected. This phenomenon is a significant part of the reason the Arctic region has warmed three to four times faster than the global average. This accelerated pace of warming in the Arctic relative to the global average is known as “Arctic Amplification,” and it has fueled a self-reinforcing feedback loop: Higher temperatures in the Arctic drive more sea ice loss. which further increases warming in the region.