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New Study Reveals Increased River Discharge to Arctic Ocean
Finding Could Mean Big Changes to Global Climate
Researchers from the Marine Biological Laboratory’s Ecosystems Center, along with an international team of hydrologists and oceanographers, have documented 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 this could impact the global climate, perhaps leading to the cooling of Northern Europe.
Ecosystems Center researchers Bruce Peterson, Robert (Max) Holmes, and James McClelland led the 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.
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Data analyzed in this study, published in the December 13, 2002, issue of Science magazine (Peterson, B.J., R.M. Holmes, J.W. McClelland, C.J. Vörösmarty, I.A. Shiklomanov, A.I. Shiklomanov, R.B. Lammers, S. Rahmstorf. 2002. Increasing River Discharge to the Arctic Ocean. Science 298:2171-2173), 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.
Date: 01/03
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