This result is published by researchers of the Alfred Wegener Institute in the journal Deep-Sea Research. The freshwater content in the layer of the Arctic Ocean near the surface controls whether heat from the ocean is emitted into the atmosphere or to ice. In addition, it has an impact on global ocean circulation.
Around ten percent of the global mainland runoff flows into the Arctic via the enormous Siberian and North American rivers in addition to relatively low-salt water from the Pacific. This freshwater lies as a light layer on top of the deeper salty and warm ocean layers and thus extensively cuts off heat flow to the ice and atmosphere. Changes in this layer are therefore major control parameters for the sensitive heat balance of the Arctic. We can expect that the additional amount of freshwater in the near-surface layer of the Arctic Ocean will flow out into the North Atlantic in the coming years. The amount of freshwater flowing out of the Arctic influences the formation of deep water in the Greenland Sea and Labrador Sea and thus has impacts on global ocean circulation.
Dr. Benjamin Rabe from the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association and his colleagues have evaluated a total of over 5,000 measured salt concentration profiles. To measure the depth distribution of the salt concentration, researchers used sensors from ships or mounted sensors on large ice floes so the data were recorded during the ice drift through the Arctic Ocean. Furthermore, measured values from submarines were inputted in the analyses. Major portions of the data stem from expeditions during International Polar Year 2007/2008. “The well coordinated research programmes in the Arctic have substantially improved the database in these difficult to access areas,” reports Rabe, who will again sail to the central Arctic on the research vessel Polarstern in the coming summer. The dense network of observations in recent years made it possible for the first time to come up with a comparative assessment of the freshwater content in the Arctic Ocean.
Rabe and his colleagues have published the increase in the freshwater content between the periods 1992 to 1999 and 2006 to 2008 in the journal Deep-Sea Research. “The considerable changes in the upper water layers primarily comprise a decline in salt concentration,” says Rabe. Another, though minor, effect is that the low-salt layers are thicker than before. The freshwater content of the Arctic Ocean may rise due to increased sea ice or glacier melt, precipitation or river inputs. Less export of freshwater from the Arctic – in the form of sea ice or in liquid form – also results in a rise in the freshwater content. The authors of the study point to altered export of freshwater and altered inputs from near-coastal areas in Siberia to the central Arctic Ocean as the most probable reasons.
Dr. Michael Karcher from the Alfred Wegener Institute, co-author of the study, simulated the observed processes using the NAOSIM coupled ocean/sea ice model. The model experiments make it possible to study longer periods, i.e. to map times for which no measurement data are available. The model also supplies important insights into the causes of the rising and falling freshwater content and points out the great significance of the local wind field. Measurements and the model additionally show that the changes in the Arctic freshwater content encompass far larger areas than assumed to date.
The title of the original publication by Benjamin Rabe, Michael Karcher, Ursula Schauer, John M. Toole, Richard A. Krishfield, Sergey Pisarev, Frank Kauker, Rüdiger Gerdes and Takashi Kikuchi is: “An assessment of Arctic Ocean freshwater content changes from the 1990s to the 2006-2008 period“ and appeared in the journal Deep-Sea Research I 58 (2011) 173-185; doi:10.1016/j.dsr.2010.12.002 (http://dx.doi.org/10.1016/j.dsr.2010.12.002).
The Alfred Wegener Institute conducts research in the Arctic, Antarctic and oceans of the high and mid latitudes. It coordinates polar research in Germany and provides major infrastructure to the international scientific community, such as the research icebreaker Polarstern and stations in the Arctic and Antarctica. The Alfred Wegener Institute is one of the seventeen research centres of the Helmholtz Association, the largest scientific organisation in Germany.
Margarete Pauls | idw
Greenland ice flow likely to speed up: New data assert glaciers move over sediment, which gets more slippery as it gets wetter
17.08.2017 | Swansea University
Climate change: In their old age, trees still accumulate large quantities of carbon
17.08.2017 | Universität Hamburg
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
18.08.2017 | Life Sciences
18.08.2017 | Physics and Astronomy
18.08.2017 | Materials Sciences