Despite the high temperatures, geologists and climate researchers find evidence that there was sea ice at the North Pole during the last interglacial
Temperatures in the Arctic are currently climbing two to three times faster than the global average. The result - and, thanks to feedback effects, also the cause - is dwindling sea ice. In a study published in the actual volume of Nature Communications, geo- and climate researchers at the Alfred-Wegener Institute, Helmholtz Centre for Polar- and Marine Research (AWI) show that, in the course of our planet's history, summertime sea ice was to be found in the central Arctic in periods characterised by higher global temperatures - but less CO2 - than today.
Prognoses for the future of the Arctic can only be as reliable as the models and data they're based on. The scenarios projected by climate modellers vary greatly, and it remains unclear when we can expect to see the Arctic Ocean free of ice in the summer.
At the same time, there is considerable public interest in dependable predictions concerning Arctic sea ice development over the next few decades, so as to have a basis for long-term strategic planning.
Researchers at the Alfred Wegener Institute have now more closely analysed the glacial history of the central Arctic with the help of sediment core data and climate simulations. Their findings indicate that the region was home to sea ice during the last interglacial, between 115,000 and 130,000 years ago.
"Thanks to the sediment core data, we have clear evidence that, during the last interglacial roughly 125,000 years ago, the central Arctic Ocean was still covered with sea ice during the summer. In contrast, in an area to the northeast of Spitsbergen, the summertime sea ice virtually disappeared," explains Prof Rüdiger Stein, a geologist at the Alfred Wegener Institute and first author of the Nature Communications study, adding, "This is also confirmed by the climate simulations run by AWI modellers involved in the study."
However, comparing the results of the climate simulations for the most recent interglacial with scenario calculations for the future reveals substantial differences: thanks to the more intense solar radiation, back then the air temperatures at higher latitudes were also a few degrees higher than at present. However, the carbon dioxide concentration in the atmosphere - roughly 290 ppm (parts per million) - was ca. 110 ppm lower than the current level, as ice core data from the Antarctic shows.
For their scenario calculations, the AWI modellers plugged in atmospheric CO2 concentrations in excess of 500 ppm, a level in keeping with the forecasts released by the Intergovernmental Panel on Climate Change (IPCC). Under these conditions, a disproportionately rapid retreat of summertime sea ice in the central Arctic Ocean over the course of the next few decades, followed by its complete disappearance - depending on how quickly CO2 levels rise - roughly 250 years from now, is to be expected.
The outcomes of the study reveal the complexity of the processes shaping climate change in the Arctic and point to significant spatial and chronological variances in sea ice cover. To slow the warming of the Arctic and the permanent loss of sea ice, reducing the level of anthropogenic CO2 emissions in the atmosphere is vital.
For the purposes of their study, the researchers used what is referred to as "proxies" - indicators that contain information on past environmental conditions. They concentrated on organic proxies, also known as biomarkers. Some of these biomarkers are produced by certain species of algae, among which one group can only be found in open surface water, while the members of another group only live in sea ice (or did so in the Earth's distant past).
"When we confirm the presence of these algal biomarkers in our sediment layers, it allows us to draw conclusions on the depositional environment and the environmental conditions at the respective time," says Stein. Since the biomarker groups they investigated are based on algae - i.e., on plants that require light for photosynthesis - the absence of both groups is an important indicator of a very thick and largely contiguous ice cover. Such conditions would make photosynthesis impossible, both for the algae in the surface water directly under the ice and those dwelling deeper in the ice close to the ice-water interface.
In addition to these valuable new insights into sea ice distribution during the last interglacial, the study also produced another exciting finding, one concerning the extent of circum-Arctic ice sheets during the Saale glaciation. As Stein relates, "Towards the end of the Saale glaciation (roughly 140,000 to 150,000 years ago), the glaciers most likely extended beyond the outer shelf. They produced masses of cold air that blew out to sea as powerful fall winds (katabatic winds) and created large expanses of open water (polynyas) - a process still frequently observed around the Antarctic continent."
These conditions would seem to contradict the hypotheses put forward by international researchers (Jakobsson et al., 2016), who postulated in 2016 that the glaciers in North America and Eurasia expanded beyond the continental shelf during the Saale glaciation and into open water, covering the entire Arctic Ocean with a nearly kilometre-thick layer of solid ice. "Yet our biomarker data show acceptable living conditions for phytoplankton and sea ice algae, namely open waters and seasonal ice cover - a wide difference to kilometre-thick ice," says Rüdiger Stein.
However, the geologist goes on to explain, "That being said, a chronological sequence of extremely extended thick ice sheets (similar to what Jakobsson et al. have postulated) followed by sea ice formation with polynyas seems to be possible, as the initial results of our own investigations on the southern Lomonosov Ridge have shown. To finally approve this, however, further detailed investigations, especially of well dated sediment cores, are needed."
Ruediger Stein, Kirsten Fahl, Paul Gierz, Frank Niessen & Gerrit Lohmann: Arctic Ocean sea ice cover during the penultimate glacial and the last interglacial. Nature Communications. doi: 10.1038/s41467-017-00552-1.
Your scientific contact partner at the Alfred Wegener Institute is: Rüdiger Stein (Tel: +49 (0)471 4831 - 1576; E-Mail: firstname.lastname@example.org)
At the AWI's Communications and Media Relations department, Folke Mehrtens (Tel: +49 (0)471 4831 - 2007; E-Mail: email@example.com) will be pleased to help you with any questions.
The Alfred Wegener Institute pursues research in the Arctic, Antarctic and the oceans of the middle and high latitudes. It coordinates polar research in Germany, while also providing essential infrastructure for the international scientific community, including the research icebreaker Polarstern and stations in the Arctic and Antarctic. The Alfred Wegener Institute is one of the 18 Research Centres of the Helmholtz Association, the largest scientific organisation in Germany.
Ruediger Stein | EurekAlert!
Gas hydrate research: Advanced knowledge and new technologies
23.03.2018 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
New technologies and computing power to help strengthen population data
22.03.2018 | University of Southampton
Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.
The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
23.03.2018 | Event News
19.03.2018 | Event News
16.03.2018 | Event News
23.03.2018 | Materials Sciences
23.03.2018 | Agricultural and Forestry Science
23.03.2018 | Physics and Astronomy