September 18, 2017

Collecting unique data where the Atlantic Water meets the Arctic Ocean: A-TWAIN2017

Posted by larryohanlon

By Gwénaëlle Hamon and Amélie Meyer, Norwegian Polar Institute

A-TWAIN is a long-term project monitoring since 2012 the variability and trends of the Atlantic Water inflow in the Svalbard region of the Arctic, led by the Norwegian Polar Institute, and funded by the Fram Centre ‘Arctic Ocean’ flagship. Every other year, an A-TWAIN cruise takes place in the autumn to gather data and service moorings for the project. Water that flows northward from the Atlantic Ocean into the Arctic Ocean plays a crucial role for environmental conditions there. A-TWAIN collects unique data on the Atlantic Water that enters the Arctic Ocean north of Svalbard, mainly through time series from moorings and high-resolution CTD (conductivity, temperature, and depth) measurements.


RV Lance docked for loading at Kullkaia in Longyearbyen, Svalbard, on September 14, 2017. Photo credit: Gwénaëlle Hamon, Norwegian Polar Institute

The 2017 cruise (A-TWAIN2017) departed from Longyearbyen (78°N), Svalbard, on September 14, 2017, to head out Northeast of Svalbard. It is meant to come back to Longyearbyen on September 26, 2017. The Svalbard archipelago is the closest point to the North Pole on the European side, which makes it a good and well-used logistic centre for Arctic research. In addition to the crew, fifteen people joined the cruise on board the Norwegian Research Vessel Lance (RV Lance), including scientists and engineers from the Norwegian Polar Institute (NPI), the Norwegian Institute of Marine Research (IMR), the University of Tromsø (UiT), the Scottish Association for Marine Science (SAMS), the Institute of Oceanology of the Polish Academy of Science (IOPAN), the University of Bergen (UiB), the Bjerknes Center for Climate Research, as well as a staff member from the WCRP CliC-Climate and Cryosphere Project office (hosted at NPI) and a TYT filming crew from Los Angeles. 


Longyearbyen, September 2017. Photo credit Gwénaëlle Hamon, Norwegian Polar Institute

Ocean moorings work as remote observatories. They are platforms that are left in the marine environment and can hold instruments along a cable anchored to the seafloor. They can thus provide long-term views of the ocean processes. The first A-TWAIN moorings were deployed in September 2012, during a cruise where a large survey of hydrography was undertaken. In 2013, the moorings were recovered, and a new spatial mapping of water masses was done. Moorings were deployed again from 2013 to 2015, and redeployed again from 2015 to 2017. During the A-TWAIN2017 campaign, three new moorings are being deployed and three from 2015 recovered. 


September 17, 2017, Recovery of an A-TWAIN mooring deployed in 2015. Photo credit: Gwénaëlle Hamon, Norwegian Polar Institute

Another instrument used during the cruise is the ship CTD rosette, which measures how the salinity and temperature of the ocean water changes relative to depth. Salinity combined with temperature, can be used to determine seawater density, a primary driving force for major ocean currents. The rosette is a large metal frame, which holds the CTD, water sampling bottles, and many other instruments. During A-TWAIN2017, two main CTD transects are being conducted as well as additional CTD stations throughout the cruise. The rosette is sent down in the water column, collecting data all along and taking water samples at several predefined depths. 


September 16, 2017, preparation of a CTD rosette before it goes down in the water column. Photo credit: Gwénaëlle Hamon, Norwegian Polar Institute

During A-TWAIN2017, microstructure data will also be collected. Such data provide information about the turbulence and mixing intensity in the water column. A microstructure profiler will be deployed either from the RV Lance or from a smaller boat to cover the upper 150 m of the ocean. Having measurements of turbulence will allow the scientists to better understand how warm Atlantic Water that is flowing in the Arctic is mixed with surrounding Arctic waters and also how much of its heat reaches the ocean surface and the sea ice.

All of these data collected at sea and the daily life on the ship would not be possible without the nine very welcoming crew members on board RV Lance. The Captain, Chief Officer, and deck crew work very closely with the scientists and engineers to help them day and night with their work. Crew members have been working on the ship for up to twelve years. Thanks to the stewardesses and cook, life on board RV Lance is very ‘koselig’ (cosy in Norwegian). Meals are served at fixed hours in the mess three times a day and coffee is always brewing.