Significant sea ice formation occurred in the Arctic earlier than previously thought is the conclusion of a study published this week in Nature.
"The results are also especially exciting because they suggest that sea ice formed in the Arctic before it did in Antarctica, which goes against scientific expectation," says scientific team member Dr Richard Pearce of the University of Southampton's School of Ocean and Earth Science based at the National Oceanography Centre, Southampton (NOCS).
The international collaborative research team led by Dr Catherine Stickley and Professor Nalân Koç of the University of Tromsø and Norwegian Polar Insitute (Tromsø) analysed oceanic sediment cores collected from the Lomonosov ridge in the central Arctic by Integrated Ocean Drilling Program Expedition 302 ('ACEX'). Previous analyses of cores drilled in this region revealed ice-rafted debris dating back to the middle Eocene epoch, prompting suggestions that ice appeared in the Arctic about 46 million years ago. But records of ice-rafted debris do not differentiate sea ice from glacial (continental) ice, which is important because sea ice influences climate by directly affecting ocean–atmosphere exchanges, whereas land-based ice affects sea level and consequently ocean acidity.
Instead of focusing solely on ice-rafted debris, Stickley and her colleagues also garner information about ancient climate by analysing fossilised remains of tiny single-celled plants called diatoms in the sediment cores. Today, different living diatom species are adapted to particular environmental conditions. Assuming that this was also true in the past – for which there is ample evidence – the presence of particular diatom species in sediment cores is diagnostic of conditions prevailing at the time.
Coincident with ice-rafted debris in the cores, the researchers found high abundances of delicately silicified diatoms belong to the genus Synedropsis. "We were astonished by this", said team member Richard Pearce of NOCS, who imaged the samples using a scanning electron microscope at the NOCS: "Weakly silicified diatoms are preserved only under exceptional circumstances, so to find fossilised Synedropsis species so well preserved and in such abundance is truly remarkable." In fact, the ACEX Synedropsis species represent the earliest known fossil record of sea-ice diatoms.
The researchers attribute the presence of Synedropsis fossils in these sediments to the presence of sea ice, and silica-enriched waters that favour their preservation. They propose that, like Synedropsis species found in polar regions today, the ACEX species were also sea-ice specialists uniquely adapted for surviving the lengthy polar darkness and freezing temperatures. "These diatoms provide the most compelling evidence for ancient sea ice, as they rely on this medium for their survival," said Catherine Stickley. Moreover, their analysis of quartz grain textural characteristics further supports sea ice as the dominant transporter of ice-rafted debris at this time.
"It is likely that sea ice formed in autumn and winter and melted in spring and summer, as seasonal sea ice does today," they say. Synedropsis species probably over-wintered within the sea ice and then bloomed there in the spring when there was enough sunlight. They would have been released into stratified surface waters as the ice melted, rapidly sinking to the sea bottom as aggregates, leaving other diatom species to dominate summer production. And, indeed, these seasonal changes can be discerned in the sediment cores.
The researchers conclude from their analysis, which cover a two-million year period, that episodic sea ice formation in marginal shelf areas of the Arctic started around 47.5 million years ago, about a million years earlier than previous estimates based on ice-raft debris evidence only. This appears to have been followed half a million years later by the onset of seasonal sea-ice formation in offshore areas of the central Arctic, and about 24 million years before major ice-sheet expansion in the region.
The findings have potentially important implications for climate. Spring sea ice and summer cloud formation would have reduced oceanic heat loss to the atmosphere and increased the amount of solar radiation reflected back out into space. "A stable sea-ice regime also suggests the possibility of concomitant glacial ice," say the researchers, and indeed they find some evidence for the presence of small isolated glaciers at the time.
Furthermore, their data indicate that sea ice formed in the Arctic before it did in Antarctica. Atmospheric levels of the greenhouse gas carbon dioxide were declining in the middle Eocene, one of the reasons postulated in causing the Earth to cool. However, the new findings imply that the threshold for sea-ice formation was first crossed in the Arctic, which, say the authors, is "a hypothesis opposite to that modelled for glacial ice, whereby Antarctica is shown to glaciate much earlier (that is, at higher levels of carbon dioxide) than circum-Arctic continents."
For more information contact the NOCS Press Officer Rory Howlett on +44 (0)23 8059 8490 Email: email@example.com
Images are available from the NOCS Press Office (Tel. 02380596100).
Dr Richard Pearce: Telephone +00 44 23 8059 6477 or +00 44 23 8059 6518; Email firstname.lastname@example.org
Notes to Editors:
The paper, 'Evidence for middle Eocene Arctic sea ice from diatoms and ice-rafted debris', is published by Nature on 16 July 2009.
This research used samples and data provided by the Integrated Ocean Drilling Program (IODP) and was supported by VISTA (Norwegian Academy of Science and Letters and StatoilHydro) and the Research Council of Norway.
The authors are: Catherine Stickley (University of Tromsø and Norwegian Polar Institute), Kristen St John (James Madison University), Nalân Koc (U. Tromsø and NPI),, Richard Jordan (Yamagata University), Sandra Passchier (Montclair State University), Richard Pearce (National Oceanography Centre, Southampton) & Lance Kearns (JMU).
The National Oceanography Centre, Southampton is the UK's focus for ocean science. It is one of the world's leading institutions devoted to research, teaching and technology development in ocean and earth science. Over 500 research scientists, lecturing, support and seagoing staff are based at the centre's purpose-built waterside campus in Southampton along with over 700 undergraduate and postgraduate students.
The National Oceanography Centre, Southampton is a collaboration between the University of Southampton and the Natural Environment Research Council. The NERC royal research ships RRS James Cook and RRS Discovery are based at NOCS as is the National Marine Equipment Pool which includes Autosub and Isis, two of the world's deepest diving research vehicles.
Dr. Rory Howlett | EurekAlert!
Further reports about: > ACEX > Antarctica > Arctic > Earth's magnetic field > Integrated Ocean Drilling Program > NOCS > Nature Immunology > Oceanography > Pacific Ocean > Science TV > Southampton > Synedropsis > carbon dioxide > diatom species > glacial ice > polar region > sea ice > sediment cores > surface water
Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie
Modeling magma to find copper
13.01.2017 | Université de Genève
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Materials Sciences
17.01.2017 | Architecture and Construction