Scientists re-write history of climate change in the Arctic

Posted on Thursday, May 18, 2017

A scientist measures an ice core

Can the past predict the future? When it comes to climate change, records of temperature variations over thousands — or even millions — of years reveal precious clues on long-term trends and how the environment will react to future temperature changes. New work by an international team of scientists has found that ice core records documenting thousands of years of climate change reveal higher temperatures than previously determined in the Arctic, one of the Earth’s most fragile ecosystems.

University of Ottawa researchers Glenn Milne and David Fisher, of the Department of Earth and Environmental Sciences; Denis Lacelle, of the Department of Geography; and MSc student Benoit Lecavalier used ice cores drilled on remote Ellesmere Island, in the northernmost part of Nunavut, to measure temperature changes in the High Arctic over the past 12,000 years. They then evaluated how the nearby Greenland ice sheet responded to these changes.

“We knew that two methodological approaches previously used to estimate temperature changes based on ice cores drilled from the Agassiz ice cap on Ellesmere Island gave inconsistent results,” explains Milne, Canada Research Chair in Earth System Dynamics. Milne says that the new methodology gave consistent results by taking into account the influence of the thinning Innuitian ice sheet in Canada’s Arctic on temperature reconstructions from Agassiz ice.

Importantly, the team found that its revised temperature record for the very early Holocene Epoch, nearly 12,000 years ago, shows temperatures that are four or five degrees warmer than previously estimated in the High Arctic, with significant implications for our understanding of climate change in the area. For starters, the revised temperatures for the Holocene Thermal Maximum, a warm period that started about 11,000 years ago and ended about 8,000 years ago, are warmer than present temperatures, which provides researchers a crucial past reference point to understand how the Greenland ice sheet responds to elevated temperatures.

“This will improve our ability to forecast how the ice sheet will respond to projected climate warming in the coming decades to centuries,” notes Fisher.

The team ran a model of changes in the Greenland ice sheet with its revised temperature data and discovered that rising temperatures caused significant ice thinning  — about one kilometre in depth —  a finding supported by ice core records from Greenland.

The new temperature record developed by the team also provides important context for recent temperature changes. “We found that, as of 2009, temperatures are at their highest level in the past 7,000-8,000 years,” explains Lacelle. “The rate of temperature change during the industrial era is also the most significant in 12,000 years.”

The new temperature record is the only continuous record of its type in the High Arctic. It provides unique insight into Arctic climate change and why the area is warming much faster than the global average. The findings also strengthen evidence that recent climate warming is happening unusually quickly and is likely caused by human activity.

Read the study in Proceedings of the National Academy of Sciences

Members of the research team
Glenn Milne, David A. Fisher, Denis Lacelle and Brittany Main (University of Ottawa), Benoit Lecavalier and Lev Tarasov (Memorial University), Bo Vinther (Centre for Ice & Climate, Niels Bohr Institute, University of Copenhagen), Philippe Huybrechts (Vrije Universiteit Brussel), James Zheng (Natural Resources Canada), Jocelyne Bourgeois (Consorminex), Arthur Dyke (Dalhousie University & McGill University)

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