Nav: Home

Tracking the amount of sea ice from the Greenland ice sheet

October 10, 2016

The Greenland ice sheet records information about Arctic temperature and climate going back to more than 120 000 years ago. But new research from the Niels Bohr Institute among others reveals that the ice doesn't just tell us about the situation in the air and on the land - it can also tell us about what was happening at sea. By analysing ice cores drilled from deep inside the Greenland ice sheet, researchers have started to calculate how much Arctic sea ice there was in the past. The results have been published in the research journal Scientific Reports.

Arctic sea ice is changing. In the past the Arctic Ocean was covered by metres of thick sea ice but now that sea ice is thinning and being replaced by sea ice that melts away over the summer. The rapid decrease of summer sea ice that we currently observe is opening up the region for shipping and exploration but also threatening local ecosystems and cultures. But what was sea ice like in the past? The amount of sea ice has only been well known since the 1970's when satellite measurements began, so we don't know what has been happening far back into the past.

Researchers at the Niels Bohr Institute in Denmark and Ca'Foscari University of Venice in Italy have discovered that chemical traces of sea ice can be found far away from the ocean within the kilometres-thick Greenland ice sheet. The ice sheet is covered by snow which falls every year and is compressed into ice over many thousands of years. Every layer of ice tells us about the year that the snow originally fell on the ice sheet - what the temperature was like and what kinds of particles were blowing around in the atmosphere at that time.

"We can measure the amount of a chemical called bromine in the Greenland ice cores. You find bromine in both the ocean and sea ice, but when new sea ice forms in the winter the sea salt is concentrated into salty pockets of brine which contain bromine. In spring and summer, the sunlight that shines down onto the sea ice starts chemical reactions. In these reactions, ozone in the air reacts with bromine in the ice and the bromine is released in greater and greater amounts from the sea ice. This process is called a bromine explosion. When it is released from the sea ice, the concentrated bromine is carried by the wind up onto the ice sheet and then deposited with the falling snow. That is the source of the bromine we measure in ice cores", explains Paul Vallelonga, Associate Professor at the Centre for Ice and Climate at the Niels Bohr Insitute, University of Copenhagen.

The reactions stop in autumn and winter, when the sun goes below the horizon and new sea ice begins to form again.

Reconstructing sea-ice in the past

It's one thing to measure the amount of bromine in an ice core from Greenland, but it's another thing to understand the connection between bromine and the amount of sea ice in the Arctic.

In order to link the bromine measurements with the amount of sea ice covering the Arctic, scientists have used satellite observations of sea ice as a measuring stick, which goes back to the 1970's. The measurements can be used to link the bromine content in the ice cores with the amount of new sea ice produced each year since 1979. A clue about the amount of sea ice in the past has also been revealed by records from Icelandic fishing communities, which go back more than 1000 years. Altogether, these data have allowed researchers to calculate how much sea ice there was in the Arctic tens of thousands of years ago.

"With this technique we can fill the gaps in our understanding of the amount of Arctic sea ice in the past. Since ice cores also reveal a lot of information about the climate, we can combine the sea ice data with the climate data and start to understand how sea ice reacts to climate change" explains Paul Vallelonga.

Sea ice and climate change

Researchers have found that 8000 years ago the Arctic climate was 2 to 3 degrees warmer than now, and that there was also less summertime Arctic sea ice than today.

"We have been in this situation before, with less sea ice and more open ocean during the warm Arctic summer. So right now we have not yet exceeded the natural boundaries for the Arctic region, but the question is: with more warming in the Arctic driven by rising greenhouse gases, how soon will sea ice melting reach and exceed the levels of 8000 years ago? These new research results can help us to answer this question when we combine them with climate models", says Paul Vallelonga.
-end-
Contact: Paul Vallelonga, Associate Professor, Center for Ice and Climate at the Niels Bohr Institute, University of Copenhagen, +45 3532-0043, vallelonga@nbi.ku.dk

University of Copenhagen - Niels Bohr Institute

Related Climate Change Articles:

The black forest and climate change
Silver and Douglas firs could replace Norway spruce in the long run due to their greater resistance to droughts.
For some US counties, climate change will be particularly costly
A highly granular assessment of the impacts of climate change on the US economy suggests that each 1°Celsius increase in temperature will cost 1.2 percent of the country's gross domestic product, on average.
Climate change label leads to climate science acceptance
A new Cornell University study finds that labels matter when it comes to acceptance of climate science.
Was that climate change?
A new four-step 'framework' aims to test the contribution of climate change to record-setting extreme weather events.
It's more than just climate change
Accurately modeling climate change and interactive human factors -- including inequality, consumption, and population -- is essential for the effective science-based policies and measures needed to benefit and sustain current and future generations.
Climate change scientists should think more about sex
Climate change can have a different impact on male and female fish, shellfish and other marine animals, with widespread implications for the future of marine life and the production of seafood.
Climate change prompts Alaska fish to change breeding behavior
A new University of Washington study finds that one of Alaska's most abundant freshwater fish species is altering its breeding patterns in response to climate change, which could impact the ecology of northern lakes that already acutely feel the effects of a changing climate.
Uncertainties related to climate engineering limit its use in curbing climate change
Climate engineering refers to the systematic, large-scale modification of the environment using various climate intervention techniques.
Public holds polarized views about climate change and trust in climate scientists
There are gaping divisions in Americans' views across every dimension of the climate debate, including causes and cures for climate change and trust in climate scientists and their research, according to a new Pew Research Center survey.
The psychology behind climate change denial
In a new thesis in psychology, Kirsti Jylhä at Uppsala University has studied the psychology behind climate change denial.

Related Climate Change Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#529 Do You Really Want to Find Out Who's Your Daddy?
At least some of you by now have probably spit into a tube and mailed it off to find out who your closest relatives are, where you might be from, and what terrible diseases might await you. But what exactly did you find out? And what did you give away? In this live panel at Awesome Con we bring in science writer Tina Saey to talk about all her DNA testing, and bioethicist Debra Mathews, to determine whether Tina should have done it at all. Related links: What FamilyTreeDNA sharing genetic data with police means for you Crime solvers embraced...