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 Naln Ko of the University of Troms and Norwegian Polar Insitute (Troms) 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 oceanatmosphere 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
|Contact: Dr. Rory Howlett|
National Oceanography Centre, Southampton (UK)