Brussels, 07 Mar 2005
A team of international scientists from the Autonomous University of Barcelona in Spain and the Potsdam Institute for Climate Impact Research in Germany has found the mechanism that sets off the accumulation of ice.
Working mainly with existing data from the remains of marine organisms built up over the years, as well as climate models, the researchers delved into the previously unresolved mystery of why ice has been building up in the Artic for 2.7 million years.
As the team explains, a sudden fall in world temperatures 2.7 million years ago triggered the freezing of the Artic Ocean and the covering in ice of North America and Europe. However, the drop in average temperatures is not enough to explain why so much ice has built up and has remained to this day. Although many different theories where put forward, this accumulation of ice remained unexplained until now.
The two teams led by Antoni Rosell from Barcelona and Gerald H. Haug from Potsdam have now found the answer. According to their research 'the most important change during the period was a seven degree Celsius increase in the difference between summer and winter temperatures within just a few centuries. The summers became warmer and the winters cooler, causing more water to evaporate from the sea into the atmosphere during the summer. The air became more humid and snowfall increased. When winter set in, the sharp decrease in temperatures enabled ice to build up,' explain the scientists.
The difference in temperatures appears to have been caused by the stratification of ocean water, due to an increase in freshwater. This, comment the researchers, meant that water mixed less than previously, forming layers of different densities in different strata and at different depth.
'When spring came, the layers closest to the surface began to heat up. Since the water did not mix, the temperature of those layers continued to rise, and increasing amounts of water evaporated. During the summer months, this effect intensified, as higher temperatures increase stratification; in winter, however, the water began mixing again, and temperatures dropped more than in previous years,' state the scientists.
The two professors and their teams recreated the seasonal changes in temperature in the North Pacific by reinterpreting the data obtained from analysing the remains of marine organisms and by checking these temperatures by means of a climate model. This reconstruction showed how the ocean, in terms of its surface temperature and its size during different seasons, as well as water evaporation from the sea, can generate momentous changes in the climate. The reconstruction also revealed more intense glacial cycles and a general cooling of the planet's temperatures.
'Through this research we can understand in greater detail why climate change occurs, and more specifically, the role of the ocean in producing climate change,' said Professor Rosell, from the Spanish team. 'This information will improve climate models used to predict how today's climate will change in the future,' he concluded.
For further information please contact:
Institute of Environmental Science and Technology (ICTA)
Universitat Autònoma de Barcelona
Tel: +36 93 581 3583