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Through the looking glass

Ice core analysis study evaluates past temperatures, Greenland melt


By Kelly Foss

A new paper led by Memorial researchers has been published in the Proceedings of the National Academy of Sciences.

The paper reconstructs past temperatures from an ice core, identifying a warmer past and demonstrating that the Greenland ice sheet is susceptible to rapid melt in a warming world.

Ice core analysis

A group of mainly Canadian researchers collected the ice samples from the high Arctic and performed the ice core analysis, a field of research that was nearly dismantled in Canada over the last decade.

Benoit Lecavalier, a PhD candidate in the Department of Physics and Physical Oceanography, is lead author on the paper, and is joined by his supervisor, Prof. Lev Tarasov.

The study used ice cores from the Agassiz ice cap, the most northerly in the world, to reconstruct temperature change from that region during the past 12,000 years.

The Agassiz ice cap is significant as it is next to the Greenland ice sheet as well as Arctic sea ice, and can therefore provide information about how both might react to today’s changing temperatures.

An ice core section drilled in Alaska.
An ice core section drilled in Alaska.
Photo: Bradley R. Markle

“This ice cap documents a warm period in Earth’s history, about 10,000 years ago, when temperatures in this region were warmer than they are today,” he explained.

“How the climate system responded in the past to this warm episode can provide us with an interesting “analogue” on how the system might change in the future as the climate keeps changing.”

Predicting the future

However, Mr. Lecavalier emphasizes that this past warm period was regional and driven by other factors than those responsible for present-day climate change.

There are many drivers and mechanisms in the Earth system that can change the climate, he says, and that it is crucial for climate scientists to test their sophisticated models against observations of the past and present to build confidence in the model’s ability to predict future changes.

Glaciers from the Greenland ice sheet draining into the ocean.
Glaciers from the Greenland ice sheet draining into the ocean.
Photo: Benoit S. Lecavalier

When the researchers reconstructed the temperature history and applied it in simulations to study the response of the Greenland ice sheet, they found that 10,000 years ago, when temperatures were a few degrees warmer than they are today, the ice sheet was losing mass about seven times faster than it is currently.

They also believe that if today’s temperatures keep warming until they are comparable to those from that time, it could imply that the ice sheet could once again lose a lot of mass very rapidly.

“This research is a looking glass into the past that can show us what is in store for us.” — Benoit Lecavalier

Mr. Lecavalier says temperatures in the region are already at their highest in about 7,000 years and the speed at which the temperatures are changing has never been seen before in the entire duration of the record.

“It is quite shocking that the Arctic is changing so rapidly,” he said.

“This research is a looking glass into the past that can show us what is in store for us.”

Exceptionally vulnerable

Mr. Lecavalier notes that during this past warm period, the northern part of the Greenland ice sheet was smaller by an amount that would raise sea level by approximately 20 centimetres.

“Twenty centimetres of sea-level change might not sound like much, but when superimposed on top of high tides and storm surges, regional sea level reaches much higher levels,” he explained.

In terms of future sea-level change, many coastal communities are exceptionally vulnerable. For those reasons, Mr. Lecavalier says it is important to understand the sensitivity of ice sheets to past warm periods since it gives insight on how much they might contribute to sea-level change in the future.

This sort of study provides information on the climate system and challenges we may face, which is necessary if we hope to adapt to and mitigate climate change.

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