Sea ice triggered the Little Ice Age, finds a new study

The study, published in Science Advances, reports a comprehensive reconstruction of sea ice transported from the Arctic Ocean through the Fram Strait, by Greenland, and into the North Atlantic Ocean over the last 1400 years.

The reconstruction suggests that the Little Ice Age—which was not a true ice age but a regional cooling centered on Europe—was triggered by an exceptionally large outflow of sea ice from the Arctic Ocean into the North Atlantic in the 1300s.

While previous experiments using numerical climate models showed that increased sea ice was necessary to explain long-lasting climate anomalies like the Little Ice Age, physical evidence was missing. This study digs into the geological record for confirmation of model results.

Researchers pulled together records from marine sediment cores drilled from the ocean floor from the Arctic Ocean to the North Atlantic to get a detailed look at sea ice throughout the region over the last 1400 years.

“We decided to put together different strands of evidence to try to reconstruct spatially and temporally what the sea ice was during the past one and a half thousand years, and then just see what we found,” said Martin Miles, an INSTAAR researcher who also holds an appointment with NORCE Norwegian Research Centre and Bjerknes Centre for Climate Research in Norway.

The cores included compounds produced by algae that live in sea ice, the shells of single-celled organisms that live in different water temperatures, and debris that sea ice picks up and transports over long distances. The cores were detailed enough to detect abrupt (decadal scale) changes in sea ice and ocean conditions over time.

The records indicate an abrupt increase in Arctic sea ice exported to the North Atlantic starting around 1300, peaking in midcentury, and ending abruptly in the late 1300s.

“I’ve always been fascinated by not just looking at sea ice as a passive indicator of climate change, but how it interacts with or could actually lead to changes in the climate system on long timescales,” said Miles. “And the perfect example of that could be the Little Ice Age.”

Full report here.