Arctic sea ice: going, going, gone
28 October 2008
Summer Arctic sea-ice is shrinking rapidly. 2007, saw record lows and 2008 followed a similar pattern. Sinhue Torres-Valdes and Richard Sanders describe the work of a major new consortium called ASBO - but not a delinquent scientist in sight.
The Arctic is a very beautiful place to work. The forces of nature are such that they make you wonder about your own role and place within the whole ecosystem. It is a privilege to sit in a laboratory on a research ship and catch sight of seabirds soaring in conditions we would struggle with for more than a few seconds.
The Arctic Ocean is central to the Earth's system. It supports life ranging from microscopic plants to fish and top predators such as polar bears. It is home to many indigenous cultures, and it is of particular importance to the global ocean circulation and the planet's climate. Each winter, tens of thousands of square kilometres of sea-ice form. This melts again in summer.
But something odd is happening. Rising global temperatures are changing the polar regions. The Arctic is one of the fastest warming regions on the planet. During the last few decades this annual cycle of freezing and melting has been gradually shifting out of balance. In autumn 2007, sea-ice reached its lowest point ever recorded. 2008 came close to surpassing this record. Computer models predict the Arctic may be ice-free in summer by 2030.
The decreasing summer ice cover has huge implications, not least geopolitical. The fall in surface area means a massive drop in available habitat for much life in the region, with a knock-on effect on ecosystem functioning.
Deploying an ice mounted sampling platform in the Canadian arctic.
The amount of freshwater entering the Arctic is changing. Glaciers are melting and the global water cycle is shifting as a result of human-induced climate change. More rain at northern latitudes means more water entering the Arctic from rivers in North America, Asia and Europe.
Freshwater floats on the dense salty water beneath. Salinity and temperature differences help drive the major ocean circulations that bring warm waters into the Arctic and push cold deep waters southwards towards the tropics. Sea ice has a role to play because it removes huge volumes of fresh water from the oceans.
But is has another role in the global climate system. Its white surface effectively reflects heat from the sun back out to space. Less ice means more dark-coloured water. Instead of reflecting heat, water effectively absorbs heat from the sun.
In 2007, NERC funded the the Arctic Synoptic Basin-wide Oceanography (ASBO) programme. ASBO is part of a huge international research effort in the polar regions over the period 2007-09 known as International Polar Year (IPY). Over 60,000 scientists from 50 nations are involved and NERC is the main funder of the international offices based at the British Antarctic Survey in Cambridge.
We identified waters from the Atlantic and Pacific oceans.
An important part of IPY is a complete survey of Arctic oceanography over two seasons to assess the state of the Arctic in the face of environmental change. This has been a large logistical operation.
In 2007, scientists from the Scottish Association for Marine Science joined a Canadian research ship to mount weather instruments on Arctic ice floes. Over the two years, the International Arctic Research Institute at the University of Alaska In Fairbanks coordinated the large international field expeditions on two Russian research ships. All this field work will be backed up by mathematical models and data analyses. We want to know what happens to sea ice as it melts, in particular the poorly-understood 'melt pond formation' which is crucial in determining the rate of ice loss.
In the ASBO consortium, we're measuring the changes in the Arctic Ocean's freshwater content. We also want to estimate how heat moves around the Arctic, both within the ocean and between ocean and atmosphere and to look at how all these factors will influence the ocean circulation over the entire Arctic basin.
We sailed along the remote rarely-sampled northern coast of Russia deploying scientific buoys and moorings that, among other things, continuously record temperature and salinity.
Arctic sea ice extent from 1978 to 2007.
The 2007 expedition was significant because it happened during the historic sea-ice low. We left from Kirkenes in northern Norway and headed straight towards the Laptev and the East Siberian Seas onboard the small Russian research vessel Viktor Buynitskiy with colleagues from Fairbanks. Here we mapped the relatively warm Atlantic waters as they travel into the Arctic Ocean along the Eurasian continental shelf.
Simply getting to these remote places was challenging. Small channels between islands choked with ice requiring large icebreakers to smash through these straits. Our small ship trailed in their wake. Ice clogged the winches we use to lower instruments and retrieve water samples. The ice must be scraped off by hand, a very time consuming and energy demanding task.
In rough seas work was often difficult and even dangerous. If the captain so decided, work stopped until conditions improve. This can be frustrating because sea time is precious. Collecting water samples with temperatures close to or below zero degrees numbs your hands and working around the clock in stormy weather, under rain, snow and freezing winds is exhausting. Each bit of data was hard won against the ocean and doubly valuable for this reason.
All the efforts we made while at sea were worthwhile once we returned to land and we could analyse samples and process data. We traced the origins of the waters in the area we sampled. Our techniques meant that we could identify waters from the Atlantic and Pacific oceans and fresh water from rivers and melting sea-ice.
The 2007 expedition was during the historic sea-ice low.
When we compared our new data with data from the past we found that the main body Atlantic Ocean water entering the Arctic appears to be thicker and warmer than the long term average for the same time of year. Also, ASBO members from the British Antarctic Survey found larger amounts of rainwater water compared with previous years and colleagues from Bangor University measured the extent of water from the Atlantic in the Arctic Ocean and patterns of heat movement into the Arctic.
As this article goes to press we have just returned from our second expedition to the same region on board the large diesel-powered icebreaker Kapitan Dranitsyn (See link to expedition blog in right column). Because we were later in the season, ice conditions were much worse than 2007 with the ship having to break through ice three to four metres thick in places.
Our work will provide information and answers to questions of global importance that have relevance to all creatures living on the planet, including ourselves. Surely you will be hearing from us in the near future.
Dr Sinhue Torres-Valdes and Dr Richard Sanders are ocean biogeochemists at the National Oceanography Centre, Southampton.
Seymour Laxon (University College London)
Sheldon Bacon (National Oceanography Centre, Southampton)
ASBO consortium partner institutions: University College London, National Oceanography Centre, Southampton, Bangor University, Scottish Association for Marine Science, British Antractic Survey, and University of Reading.
The second part of the ASBO expedition left Tromso in northern Norway on 29 September 2008.
Interesting? Spread the word using the 'share' menu on the top right.