Researchers identify Greenland meltwater in the ocean

Oct 19, 2018

As yet no impact on Gulf Stream circulation by influx from Greenland

An iceberg near Greenland. The submarine meltwater produced here has affected sea level, but so far has had no effect on the Gulf Stream circulation. Photo: MARUM – Center for Marine Environmental Sciences, University of Bremen; V. Diekamp

Bremen researchers have demonstrated that submarine meltwater from Greenland has not yet advanced into the key regions of Gulf Stream circulation. The Gulf Stream is analogous to a domestic climate-control system, transporting warm water to the north and cold water to the south. If this system is disturbed the Gulf Stream circulation will weaken and accelerate the impacts of climate change. The study, financed by the German Research Foundation (DFG – Deutsche Forschungsgemeinschaft), has been published in the journal Geophysical Research Letters.

Over the past 20 years, the melting rate of the Greenland Ice Sheet has almost quadrupled, thus significantly contributing to the global rise in sea level. There are two general causes for the acceleration of glacial-ice melting. Firstly, the atmosphere is warming. The second reason is that the warmer waters of the Gulf Stream are flowing into fiords with glaciers – melting them from below the sea surface. Scientists call the resulting effluent submarine meltwater. This freshwater could then contribute to a weakening of Gulf Stream circulation, which is very relevant to climate development.

Scientists rely on modelling results to study how this additional meltwater influences the Gulf Stream circulation in the North Atlantic Ocean. The rates and directions of meltwater dispersion are vital to these models. This submarine meltwater has now been positively identified in the ocean for the first time.

“Ice contains air bubbles. When glaciers melt, the inert gases helium and neon from the bubbles are dissolved in ocean water and their concentrations are multiplied significantly,” explains Prof. Dr. Monika Rhein of the Institute for Environmental Physics and MARUM – Center for Marine Environmental Sciences at the University of Bremen. Meltwater concentrations of less than one part per thousand can be detected from this signal. The highest concentrations of submarine meltwater – at 0.6 per cent, or six parts per thousand – were identified on the shelf margin near Greenland and Canada. So far, no meltwater has been detected in the central Labrador Sea between Greenland and Canada, the key region of Gulf Stream circulation.

Contact:
Prof. Dr. Monika Rhein
Institut für Umweltphysik, MARUM – Zentrum für Marine Umweltwissenschaften der Universität Bremen
Phone: 0049 421 218 62160
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Using state-of-the-art methods and through participation in international projects, MARUM investigates the role of the ocean in the Earth’s system, particularly with respect to global change. It quantifies the interactions between geological and biological processes in the ocean and contributes to the sustainable use of the oceans.

Inert gas measurements were carried out in Bremen with a special high-sensitivity mass spectrometer. Photo: University of Bremen

Original Publication:

Rhein, M., Steinfeldt, R., Huhn, O. Sültenfuß., J., & Breckenfelder, T. (2018).Greenland submarine melt water observed in the Labrador and Irminger Sea. Geophysical Research Letters, 45. DOI: 10.1029/2018GL079110

Additional information on the function of Gulf Stream circulation