The Arctic – a fragile system

Over the past few decades, the Arctic has warmed faster than the rest of the planet. One of the most visible signs of this is the shrinkage of the Arctic sea-ice pack. In the early 1980s its average size at the end of summer was 8 million km2. By the summer of 2007, it had dwindled to just 4 million km2, a record low.

However, it is not just the ice extent that is changing. Early findings from the DAMOCLES project indicate that the remaining ice is getting much thinner too, and the perennial sea ice is being gradually replaced with new (first year) ice. Meanwhile, the onset of pack ice formation in winter is getting steadily later, and in summer over half the ice is covered in ponds of meltwater. It is the suddenness of these changes which led the DAMOCLES team to conclude that an ice-free Arctic could become a reality far sooner than many had predicted.

The Arctic sea-ice pack plays an important role in the global climate system. Because the sea-ice is white and consequently has a high albedo, it reflects 80 % of the incoming solar radiation back out into space. However, when the ice melts, the ocean surface is exposed.

As the ocean is darker in colour, it readily absorbs 80 % of the sun’s energy, causing ocean temperatures to rise and making it harder for new ice to form.

The disappearance of the pack ice in summer and the subsequent warming of the upper layers of the ocean and lower atmosphere could accelerate the melting of Greenland’s vast ice cap. This could cause sea levels to rise by as much as a metre by the end of the century, wiping low lying countries such as Bangladesh and small island states like Tuvalu off the map. Several major cities, including London, Tokyo, New York and Mumbai could also be affected.

In addition to this, the flow of freshwater from Greenland into the sea would reduce the salinity of the north Atlantic. This could disrupt the Gulf Stream, which carries warm water from the tropics up to western Europe. When the Gulf Stream reaches the cooler climes of the Arctic, it becomes denser and sinks to the bottom of the ocean. Because freshwater is less dense than salty water, a reduction in the salinity of the north Atlantic could prevent the Gulf Stream from sinking and effectively stop it in its tracks. This would trigger a drastic cooling in western Europe, and could also cause the tropical rainbelt to shift.

At the regional level, the loss of the sea-ice pack will also have serious con se quences for Arctic wildlife, and changing environmental conditions will affect the region’s fisheries.

The shrinkage of the Arctic sea-ice pack has serious socio-economic implications. Shipping in the region is likely to become more intense, and easier access to the region will facilitate oil and gas exploration and exploitation activities. These activities have the potential to seriously damage the fragile Arctic environment, and the consequences of an oil spill or industrial accident would be catastrophic.

DAMOCLES – turning the Arctic into a laboratory

Compared to other parts of the world, we have relatively little data on the Arctic climate system, and this is hampering efforts to understand the Arctic environment. To overcome this problem, DAMOCLES is peppering the region with state-of-the-art instrumentation.

Buoys attached to the ice measure the temperature and salinity of the ocean, as well as air temperature and pressure.

Below the ice, gliders travel through the ocean at different depths measuring temperature, salinity and pressure. Other devices anchored to the seabed enable scientists to monitor the state of the ocean in a specific place over a long period of time. Yet more instruments are devoted to measuring the thickness of the ice.

Many of these devices transmit their data to satellites, allowing scientists to monitor the situation in real time. In addition to the data coming from the instruments in the Arctic, the scientists are making use of satellite images to build up a more complete picture of what is going on.

One of the project’s most exciting ventures involves a research boat called Tara that was encased in the Arctic ice pack for a year and a half. During that time, she followed the Arctic drift, while her crew gathered data from the ice, the ocean below and the atmosphere above.

Another boat which has made a vital contribution to the project is the Vagabond, which is effectively an Arctic base camp for DAMOCLES in the Svalbard Archipelago. The Vagabond’s crew has been heavily involved in testing the new technology designed for the project.

Using computer models to paint a picture of the future

The challenge now for the DAMOCLES team is to analyse the data generated by the project and use it to develop models that will be able to reliably predict the fate of the Arctic sea-ice and determine more precisely the consequences of its loss.

Meanwhile, the initial project results highlight not only the urgency of the situation, but the fact that the loss of the Arctic ice sheet will have repercussions which will extend far beyond the confines of the Arctic Circle.