Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers report on changes in Arctic sea ice after return of RV Polarstern

06.10.2011
Young and thin instead of old and bulky: In the central Arctic the proportion of old, thick sea ice has declined significantly. Instead, the ice cover now largely consists of thin, one-year-old floes.

This is one of the results that scientists of the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association brought back from the 26th Arctic expedition of the research vessel Polarstern.

The ship arrived at its home port of Bremerhaven at about 7 o’clock this morning. Prior to that it had covered more than 11,800 nautical miles on its 16-week research voyage and accommodated around 130 scientists from six countries on the three legs. The last stage took them through the central Arctic Ocean and the Polarstern also reached the North Pole. One of the most important research questions was: Did sea ice melt to a greater extent this summer, making it thinner than in past years?

To answer it, the sea ice physicists headed by Dr. Marcel Nicolaus and Dr. Stefan Hendricks employed a measuring instrument called “EM Bird”. This nearly four-metre-long, torpedo-shaped probe is flown over the ice with a helicopter and measures the ice thickness by means of an electromagnetic induction method. In this way the sea ice physicists created an ice thickness profile of the central Arctic over a total distance of more than 2,500 flown kilometres. Their conclusion is: at sites where the sea ice was mainly composed of old, thicker ice floes in the past decades there is now primarily one-year-old ice with an average thickness of 90 centimetres. Only in the Canadian Basin and near the Severnaya Zemlya island group in northern Siberia did the sea ice physicists encounter significant amounts of several-year-old ice. As a rule, this old ice is between two and five metres thick.

Compared to their measurements from 2007, when the extent of the sea ice had diminished to a record minimum of 4.3 million square kilometres, the researchers have not yet found any differences, however. “The ice has not recovered. This summer it appears to have melted to exactly the same degree as in 2007. Yes, it is exactly as thin as in the record year,” says Hendricks.

The researchers detected significant differences in places where ice was lacking this summer – in the Laptev Sea, for example. “On our expedition in 2007 we encountered thin, newly formed ice in the Laptev Sea in September. This time, however, there was no sign of ice formation anywhere. The water temperature at a depth of ten metres was three degrees Celsius – that is how much the sun had heated the ice-free water surface,” says Prof. Dr. Ursula Schauer, scientific head of the leg through the central Arctic. However, this warming is restricted only to the top layers. In the depths of the Arctic Ocean colder water from the Atlantic currently provides for falling water temperatures.

The sea ice physicists also made major advances in connection with the question of how much sunlight penetrates through the ice. For this purpose they utilised for the first time an underwater vehicle with remote control via cable. The so-called ROV (Remotely Operated Vehicle) dived to a depth of 100 metres below the ice and made large-scale recordings of the distribution of sunlight under the ice using a spectral radiometer. “Our measurements have shown that the quantity of light under the ice depends to a considerable extent on the type of ice. Several-year-old ice lets the least amount of light through because it has few melt ponds and a thick layer of weathered ice on its surface,” says Nicolaus. One-year-old ice, by contrast, is more pervious to light, especially in areas with many melt ponds. The researchers measured the greatest amounts of light under new ice. “From these results we can conclude that the observed change from a several-year-old ice cover to a seasonal Arctic ice cover will lead to an increase in light in the Arctic Ocean, particularly in summer and autumn,” states Nicolaus.

Changes in sea ice thickness and extent also have direct consequences for the ecosystem of the Arctic Ocean. The reason is that the marginal ice zone is sort of like a “Garden of the Arctic Ocean”. Due to the melting of sea ice, algae are released from the ice into the sea. In addition, the freshwater in the ice mixes with the seawater. Since the former has a lower density than seawater, a stable stratification of the surface water occurs. As a result, the algae remain in the topmost, light-flooded water layer and start to grow. So-called algal bloom results. These algae, in turn, form the beginning of the Arctic food webs. Currently it is scientifically controversial, however, whether the Arctic Ocean will become “more productive” because of the decline in ice and the related increase in light.

Scientists like Dr. Ilka Peeken therefore investigated the biology of the algae not only in the sea ice, but also in the melt ponds and in the water column under the ice. The initial results point to regional differences: in the Atlantic part of the central Arctic the algae biomass and carbon intake, both in the ice and in the melt ponds and water column, were significantly higher than in the Pacific section.

This applies similarly to the climate-relevant trace gas methane, which may form during algal bloom. Measurements by the biogeochemists headed by Dr. Ellen Damm showed that the formation and release of the greenhouse gas are influenced by which region of the Arctic Ocean is seasonally ice-free. In addition, the researchers succeeded for the first time in verifying how much methane is oxidised to carbon dioxide in the ice.

The scientists now want to compare these and many other snapshots of the situation in summer 2011 with their results from 2007 as well as with data from the two Arctic long-term observatories of the Alfred Wegener Institute in the Fram Strait. The so-called “mooring” and the deep-sea observatory HAUSGARTEN were the destinations of the first two expedition legs. Their various measuring devices have to be replaced at regular intervals, the data must be read out on board the Polarstern and the sensors have to be recalibrated. Only in this way is it possible to record environmental changes in detail.

The Polarstern is currently at the Lloyd shipyard for routine maintenance work and is expected to set off on the next expedition to the Antarctic on 28 October 2011.

The Alfred Wegener Institute conducts research in the Arctic, Antarctic and oceans of the high and middle 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.

Ralf Röchert | idw
Further information:
http://www.awi.de
http://www.geo.de

More articles from Earth Sciences:

nachricht NASA sees the end of ex-Tropical Cyclone 02W
21.04.2017 | NASA/Goddard Space Flight Center

nachricht New research unlocks forests' potential in climate change mitigation
21.04.2017 | Clemson University

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

Im Focus: Quantum-physical Model System

Computer-assisted methods aid Heidelberg physicists in reproducing experiment with ultracold atoms

Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...

Im Focus: Glacier bacteria’s contribution to carbon cycling

Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.

A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

New quantum liquid crystals may play role in future of computers

21.04.2017 | Physics and Astronomy

A promising target for kidney fibrosis

21.04.2017 | Health and Medicine

Light rays from a supernova bent by the curvature of space-time around a galaxy

21.04.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>