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Scientists investigate climate change impact on Arctic Ocean's dense water cascades

Climate change is touching all corners of the planet, both above and below the Earth's surface. One of the areas most sensitive to changes in temperature is the Arctic, but scientists hope to provide insight into how to best protect this region. One of the teams active in the ...

Climate change is touching all corners of the planet, both above and below the Earth's surface. One of the areas most sensitive to changes in temperature is the Arctic, but scientists hope to provide insight into how to best protect this region. One of the teams active in the field is using EU funding to investigate the relationship between the area's dense water cascading phenomenon and climate change in a region west of the Svalbard Islands, located between Norway and the North Pole. Their research is funded in part by the HERMIONE ('Hotspot ecosystem research and Man's impact on European seas') project, which received EUR 8 million under the Environment Theme of the EU's Seventh Framework Programme. The team is led by the University of Barcelona (UB) in Spain, and is hoping to expand knowledge of how deep-sea ecosystems work, determine how they contribute to the production of goods and services, and pinpoint how human activity affects the ocean floor. Cooling or evaporating surface waters form dense water cascades, which frequently transfer matter and energy to the seabed, effectively carrying oxygen and nutrients to areas far below the ocean's surface. When surface waters fail to cool adequately, triggered by environmental factors like global warming, the transfer process could stop, which would in turn impact the equilibrium of deep-sea ecosystems. 'Thousands of metres below the surface, the cascading mechanism is yet more proof of the creeping influence of climate change,' said lead author Miquel Canals, head of UB's Marine Geosciences Research Group The Arctic Ocean is one of the best areas to study the cascading phenomenon. The team, aboard the RV Jan Mayen research cruise that is operated by the University of Tromso in Norway, installed a series of state-of-the-art instruments on the seabed to record data on dense water cascades and evaluate their impact on the marine ecosystem and deep-sea areas. 'Our aim is to understand the dynamics of cascading in polar latitudes and to study environmental changes that the phenomenon could bring about on the ocean floor,' explained Anna Sànchez-Vidal, a researcher from UB's Department of Stratigraphy, Palaeontology and Marine Geosciences. 'To obtain data, we have installed four mooring lines with current meters and sediment traps at depths of 1,000, 1,250, 1,500 and 2,000 metres,' she added. Oceanographic and geochemical data will be recorded at regular intervals. This data will be collected next summer. 'The data will give us a time series of measurements showing the properties of water masses at different times (speed and direction of current, temperature, salinity, turbidity etc) and the sediment transport profile,' Dr Sànchez-Vidal pointed out. Tests on microorganisms will add value to the data, particularly because they are key indicators of environmental changes in deep-sea ecosystems. While the Mediterranean Basin has been a popular site for research into the cascading phenomenon, the Arctic offers scientists a diverse series of conditions. 'The surface of the Arctic Ocean is divided between one part that remains frozen throughout the year and another, much larger part that freezes during the winter, which leads to a different pattern of cascading,' explained Dr Antoni Calafat, a geologist also from UB's Department of Stratigraphy, Palaeontology and Marine Geosciences. 'Ice is a good thermal insulator. In addition, in the Arctic we also find polynas, which are areas of open water surrounded by surface ice, where the wind cools surface water masses and accelerates the formation of dense water,' he added. 'However, this process is dependent on seasonal conditions and can vary from year to year. The relief of the ocean floor is also different in the Arctic to that of the Mediterranean Basin, and the cascading process could drag large quantities of organic matter to deeper areas.' Commenting on how the relief of the ocean floor impacts current dynamics during cascading, UB's Ruth Duran said: 'The morphological parameters of the Svalbard Islands are very different to those of the Mediterranean Basin. We know that morphology, as in the case of Cap de Creus, determines the intensity and direction of currents in the Mediterranean. So during the expedition we produced detailed maps of the ocean floor in the study area - covering some 2,600 square kilometres - that had not been fully charted until then, and this enabled us to determine the precise locations to install the mooring lines.' Scientists from France, Italy, Norway and Spain contributed to the study.

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Spain, France, Italy, Norway

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