Much has been made about global sea ice the last several years. Thatâ??s largely due to the fact Arctic sea ice is showing a decline over the last several years. The record low summer ice coverage was first measured in 2007 and then coverage went even lower in 2012. The downturn has not continued, though coverage during the melt season is still below the long-term satellite average (which, by the way, only began in 1979) (Image 1 above).
Sea ice is largely controlled by the oceans, not the summer temperatures in the Arctic. In fact, they are running near to below average and last year was the coldest summer there since records began in 1958 (Image 2). Warm ocean water probably flows in from the south and melts the ice from below. The atmosphere also plays a role in ice coverage. A storm can break up and move a lot of ice into warmer southern waters where it melts.
Speaking of south, the Antarctic on the other hand, is seeing record high sea ice coverage (Image 3). The Southern Hemisphere is in the depths of winter and ice coverage is well above average. There have been some twisted explanations that have alluded to the fact that there is so much melt on the continent of Antarctica that the fresh water flowing into the ocean is freezing much more effectively than salt water. It is true that fresh water freezes at a higher temperature than salt water, but the fact that this reasoning is used to explain the increase in ice is absolutely incorrect. Here is a link to current Antarctic temperatures. All temperatures are in Fahrenheit and all are below freezing, most way below zero. There is no melting currently on the Antarctic continent.
Globally, sea ice coverage is doing just fine. When the Arctic and Antarctic are combined, the total is actually above the 1979-2010 long-term average (Image 4).