Rescuing important ocean climate observations for the Coordinated Arctic Acoustic Thermometry Experiment (CAATEX)

Once again, the ice breaker KV Svalbard has set course for the Arctic Ocean. Onboard are NERSC researchers Hanne Sagen and Espen Storheim who plan to retrieve equipment from the CAATEX-project to prevent data loss. This mission was planned on short notice – exceptional circumstances made it necessary. 

 

Scientists from Nansen Environmental and Remote Sensing Center (NERSC), Scripps Institution of Oceanography (SIO), Woods Hole Oceanographic Institution (WHOI), Institute of Oceanology Polish Academy of Sciences (IOPAN) and Norwegian Meteorological Institute (METNO) are taking part in a 5-week long expedition with the coast guard ship KV Svalbard into the Arctic Ocean. The main mission is to recover three moorings in the Beaufort Sea North of Alaska which carry acoustic and oceanographic instruments. The instruments in the moorings bring important measurements to observe the ocean climate change. The moorings are part of a trans Arctic observing system measuring the mean ocean temperature across the whole Arctic Basin using acoustic thermometry. The new observations will be compared to similar measurements made in the 1990s. This is a unique opportunity to quantify how much the ocean under the ice has warmed during the last 20 years.

 

First mooring recovery was made for the INTAROS mooring North of Svalbard. This recovery was made in open water and relatively calm sea. Jim Ryder from WHOI and Espen Storheim from NERSC are taking care of the profiling instrument on deck.: Photo: Hanne Sagen, NERSCFirst mooring recovery was made for the INTAROS mooring North of Svalbard. This recovery was made in open water and relatively calm sea. Jim Ryder from WHOI and Espen Storheim from NERSC are taking care of the profiling instrument on deck.: Photo: Hanne Sagen, NERSCSound propagates faster in warm water than in cold water. The acoustic thermometry concept builds on measuring how fast the sound signals propagate. These measurements require accurate time keeping. During the experiment one clock is running continuously. This clock is not as accurate as needed, and a very accurate atomic clock is turned on once a day to provide accurate times to correct the less accurate clock. The atomic clock draws a lot of energy and will stop this winter. If the clock stops it will not be possible to do the clock corrections properly, and the accuracy of the measurements is severely reduced. To rescue these important measurements, it is urgent to recover the moorings before the batteries are empty. This is the mission of the ongoing scientific expedition to the Beaufort Sea.

 

So why was this job not done earlier this summer? Well, the plan was to recover the moorings in September with USCG Healy. However, due to a fire in one of the engines, the cruise was cancelled just after the ice breaker left the harbor in Alaska. As soon as the situation occurred a request for assistance was sent from NERSC to the Norwegian Coast Guard. Based on a risk assessment the Coast Guard decided to help the CAATEX project to get back their moorings in the Beaufort Sea using their ice breaker KV Svalbard.

 

Agnieszka Beszczynska-Möller (IOPAN) downloading ocean data from the instruments in her mooring recovered North of Svalbard. Matthew Dzieciuch from SIO sitting in the background: Photo: Hanne Sagen, NERSCAgnieszka Beszczynska-Möller (IOPAN) downloading ocean data from the instruments in her mooring recovered North of Svalbard. Matthew Dzieciuch from SIO sitting in the background: Photo: Hanne Sagen, NERSCKV Svalbard and the Norwegian coast guard have previously supported the CAATEX project in 2019 and 2020 respectively, to deploy and recover similar moorings in the Nansen Basin. KV Svalbard is now on its way to the mooring locations in the Beaufort Sea. It is an experienced ship crew and team of researchers on board who know the operations well, but they are also prepared for challenges during transit and during the operations caused by darkness and fast-growing ice. The success of the expedition depends on routinely up-dated sea ice information, including ice charts, satellite images and forecast models. The data is gathered from different providers in Norway, USA and Russia and collated and delivered to the ship by METNO in files suitable for the limited bandwidth available on the ship.

 

During the transit the researchers and crew onboard are helping out other projects. The oceanographic mooring operated by IOPAN in the south western Nansen Basin was successfully recovered on October 24th from the Norwegian Coast Guard KV Svalbard. The mooring was deployed in 2019 as part of the Integrated Arctic Observation System project INTAROS. Year-long measurements of ocean temperature, salinity and currents covering the entire water column were collected to study the variability of the Atlantic inflow to the Arctic Ocean.

 

In support of the International Arctic Buoy Program (IABP) and the Global Drifter Program (NOAA), ten surface drifting buoys and two ice buoys will be deployed during the cruise. The buoys are measuring sea surface temperature, atmospheric pressure and their position for estimation of the near surface ocean currents. The data are delivered in real time and used by scientific community active in forecasting systems. In addition, in-situ sea ice observations will be collected throughout the cruise as part of the Ice Watch program, currently run by METNO.