Arctic Sea Ice was Present for 2.6 Million Years: Now, It May Be Disappearing

Although we haven't seen an ice free period in the Arctic for 2.6 million years, we may actually see it in our lifetimes if warming continues. Scientists have taken a closer look at Arctic ice and have found when year-round ice first formed and remained.

In order to better understand the past ice extent, the scientists studied the Arctic Ocean as it was from 5.3 to 2.6 million years ago. This was a period during which the Earth experienced a climate that, on average, was warm before our planet succumbed to cold ice ages alternating with mild interglacials.

"When we studied molecules from certain plant fossils preserved in sediments at the bottom of the ocean, we found that large expanses of the Arctic Ocean were free of sea ice until four million years ago," said Jochen Knies, one of the researchers, in a news release. "Later, the sea ice gradually expanded from the very high Arctic before reaching, for the first time, what we now see as the boundary of the winter ice around 2.6 million years ago."

About four and five million years ago, the extent of sea ice cover in the Arctic was much less. In fact, the maximum winter extent didn't reach its current location until about 2.6 million years ago.

This research, in particular, is of great interest to the international stage since present-day warming is strongly tied to shrinking ice cover in the Arctic Ocean. It's likely that by the end of the present century, the Arctic Ocean may be completely free of sea ice, especially in the summer.

So what does this mean? It will have major implications for our planet's climate system.

"Our results can be used as a tool in climate modelling to show us what kind of climate we can epect at the turn of the next century," said Knies. "there is no doubt that this will be one of many tools the UN Climate Panel will make use of, too. The extent of the ice in the Arctic has always been very uncertain but, through this work, we show how the sea ice in the Arctic Ocean developed before all the land-based ice masses in the Northern Hemisphere were established."

The findings are published in the journal Nature Communications.