New Study Reveals Increased River Discharge to Arctic Ocean

11 Dec. 2002

New Study Reveals Increased River Discharge to Arctic Ocean

Finding Could Mean Big Changes to Global Climate

WOODS HOLE, MA, USA and POTSDAM, GERMANY-An international team of hydrologists and oceanographers report in this week's issue of Science magazine that the flow of freshwater from Arctic rivers into the Arctic Ocean has increased significantly over recent decades. If the trend continues, some scientists predict that this could impact the global climate, perhaps leading to the cooling of Northern Europe.

Bruce J. Peterson of the Marine Biological Laboratory's Ecosystems Center led the research team of scientists from the United States, Russia, and Germany. They analyzed discharge data from the six largest Eurasian rivers that drain into the Arctic Ocean. These rivers, all located in Russia, account for more than 40% of total riverine freshwater inputs to the Arctic Ocean.

Peterson and his colleagues found that combined annual discharge from the Russian rivers increased by 7% from 1936 to 1999. They contend that this measured increase in runoff is an observed confirmation of what climatologists have been saying for years-that freshwater inputs to the Arctic Ocean and North Atlantic will increase with global warming. "If the observed positive relationship between global temperature and river discharge continues into the future, Arctic river discharge may increase to levels that impact Atlantic Ocean circulation and climate within the 21st century," says Peterson.

A significant increase of freshwater flow to the Arctic Ocean could slow down or shut off the North Atlantic Deep Water formation, the driving factor behind the great underwater "conveyor belt" current known as thermohaline circulation. Thermohaline circulation is responsible for moving great amounts of thermal energy around the globe, influencing the planet's climate. One of the potential effects could be cooling of Northern Europe.


Data analyzed in this study is important because it represents net precipitation (precipitation minus evapotranspiration) over a vast area, in contrast to point measurements of precipitation and evapotranspiration which are difficult to extrapolate to a large area. "This data is a unique measure of an environmental trend both in terms of how long the time series is and in that it integrates over a vast area rather than just measuring a precipitation trend at a few locations," says co-author Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research.

Project scientists are hopeful that this study, which links the work of hydrologists and oceanographers, will stimulate the two fields of science to better communicate their scientific findings with each other. The group will focus their future work on the links between the atmospheric, continental, and oceanic components of the Arctic hydrologic cycle and on the biogeochemical tracers that allow scientists to follow the circulation of riverine freshwater throughout the northern oceans. This research is needed to better understand the current functioning of the linked land-ocean-atmosphere hydrologic system and improve confidence in predictions of the future behavior of the system.

This project was funded by the Arctic System Science Program of the National Science Foundation.

Note to Editors: The paper entitled "Increasing River Discharge to the Arctic Ocean" will be published in Science on December 13. To obtain a copy of the paper and an accompanying Science news story on the paper, please contact Science directly at

202-326-6440 or Note that the news story will be available on Wednesday, December 11.

Authors are:

Bruce J. Peterson, Robert M. Holmes, James W. McClelland, The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA USA

Charles J. Vörösmarty, Richard B. Lammers, Alexander I. Shiklomanov, Water Systems Analysis Group, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH USA

Igor A. Shiklomanov, State Hydrological Institute, St. Petersburg, Russia

Stefan Rahmstorf, Potsdam Institute for Climate Impact Research, Potsdam, Germany

The Marine Biological Laboratory of Woods Hole, Massachusetts, USA, is an independent scientific institution, founded in 1888, that undertakes the highest level of creative research and education in biology, including the biomedical and environmental sciences. The research of the MBL's Ecosystems Center, which was established at the MBL in 1975, is focused on the study of natural ecosystems. Among the key environmental issues being addressed are: the ecological consequences of global climate change; tropical deforestation and its effects on greenhouse gas fluxes; nitrogen saturation of mid-latitude forests; effects of acid rain on North American lakes; and pollution and habitat destruction in coastal ecosystems of the United States.

The Potsdam Institute is a government-funded research institute devoted to interdisciplinary study of global climate change, its causes and its impacts on ecosystems and society. It was founded in 1991 in Potsdam near Berlin, Germany.