In a report, published in the August 25, 2006 issue of the journal, Science, MBL (Marine Biological Laboratory) senior scientist Bruce J. Peterson and his colleagues describe a first-of-its-kind effort to create a big-picture view of hydrologic trends in the Arctic. Their analysis reveals that freshwater increases from Arctic Ocean sources appear to be highly linked to a fresher North Atlantic.
"The high-latitude freshwater cycle is one of the most sensitive barometers of the impact of changes in climate and broad-scale atmospheric dynamics because of the polar amplification of the global warming signal," says Peterson. "It's easiest to measure these changes in the Arctic and the better we understand this system, the sooner we will know what is happening to the global hydrologic cycle."
The multi-disciplinary team of scientists led by Peterson calculated annual and cumulative freshwater input anomalies (deviations from expected levels) from net precipitation on the ocean surface, river discharge, net attrition of glaciers, and Arctic Ocean sea ice melt and export for the latter half of the 20th century. The scientists compared the fluxes to measured rates of freshwater accumulation in the North Atlantic during the same time period.
Their analysis showed that increasing river discharge and excess net precipitation on the ocean contributed the most freshwater (~20,000 cubic kilometers) to the Arctic and high-latitude North Atlantic. Sea ice reduction provided another ~15,000 cubic kilometers of freshwater, followed by ~2,000 cubic kilometers from melting glaciers. Together, the sum of anomalous inputs from all of the freshwater sources analyzed matched the amount and rate at which fresh water accumulated in the North Atlantic during much of the period from 1965 through 1995.
"This synthesis allows us to judge which freshwater sources are the largest, but more importantly shows how the significance of different sources have changed over the past decades and what has caused the changes," says Peterson. "It prompts us to realize that the relative importance of different sources will change in future decades. Creating a big-picture or synoptic view of the changes in various components of the high-latitude freshwater cycle puts the parts in a perspective where we can judge their individual and collective impact on ocean freshening and circulation."
In recent years, much attention has been given to the observed freshening of Arctic Ocean and North Atlantic and the potential impacts it may have on the earth's climate. Scientists contend that a significant increase of freshwater flow to the Arctic Ocean could slow or halt the Atlantic Deep Water formation, a driving factor behind the great "conveyor belt" current that is responsible for redistributing salt and thermal energy around the globe, influencing the planet's climate. One of the potential effects of altered global ocean circulation could be a cooling of Northern Europe within this century.
The team's comparison of freshwater sources and ocean sink records revealed that over the last half century changes in freshwater inputs and ocean storage occurred not only in conjunction with one another, but in synchrony with rising air temperatures and an amplifying North Atlantic Oscillation (NAO), a climatic phenomenon that has strong impacts on weather and climate in the North Atlantic region and surrounding continents, and the associated Northern Annular Mode (NAM) index.
Peterson and his colleagues contend that the interplay between the NAO and NAM, and continued rising temperatures from global greenhouse warming, will likely determine whether the Arctic and North Atlantic Oceans will continue to freshen. But the scientists caution that the difficultly in predicting fluctuations in atmospheric circulation makes it impossible to know where we might be headed.
"Atmospheric modes of circulation such as the NAO and NAM exert a great deal of control on net precipitation in the ocean and even on regional temperatures, and hence ice melt as well," says Peterson. "But what drives the NAO is the $64,000 question. Our inability to predict trends in the NAO/NAM means that, even if we could predict global warming very well, a large degree of uncertainty will remain in any forecasts of the decadal-centennial trajectories of the Arctic freshwater balance."
Gina Hebert | EurekAlert!
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences