New data on Atlantic inflow to the Arctic Ocean reveal effects on sea ice and marine ecosystems

 

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Deck of RV Lance seen from main mast. Photo: Amy Cooper, Woods Hole Oceanographic Institute. Front photo: Deploying hydrographic instrument and water sampling device. Photo: Vladimir Pavlov, Norwegian Polar Institute. Click on frame for full wiew.

By Arild Sundfjord, Norwegian Polar Institute and Flagship leader Sea ice in the Arctic Ocean, technology and agreements

Atlantic Water flows into the Arctic in two branches near Svalbard. One branch follows the outer perimeter of the Yermak Plateau north-west of Svalbard and then turns eastward, flowing as a wide, slow and semi-deep current along the outer, deep part of the continental slope. The other branch is warmer, faster and is found near the surface, following the upper part of the slope north of Svalbard. This large current system carries an enormous amount of heat and salt into the region – of similar magnitude as the Barents Sea Branch but with higher temperature when it enters the Arctic Ocean proper. It also brings a continuous supply of nutrients for primary production (phytoplankton growth) and transports living organisms of lower-latitude Atlantic origin into the area.

Understanding

The primary objective of this project, funded by the Fram Centre “Arctic Ocean” flagship, is to understand how heat from the Atlantic Water influences the Arctic Ocean sea ice cover, but also to provide data for understanding the playing field for some of the key actors in the ecosystem, and components of the carbon system. A-TWAIN (Long-term variability and trends in the Atlantic Water inflow region) was established to gain understanding on how the inflowing current system is distributed at different depths along the continental slope, how it responds to local, short lived atmospheric changes, and how it varies on seasonal and inter-annual timescales.

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Preparing hydrographic instrument and water sampling device. Photo: Vladimir Pavlov, Norwegian Polar Institute.

Sensors

In the first year, a total of nine instrument moorings were deployed (see map). The moorings all contain current meters plus salinity and temperature sensors, which together allow us to calculate fluxes of heat and salt. Some of the moorings also have sensors for chlorophyll, organic material and the key nutrient nitrate. Three moorings were provided through the Fram Centre Arctic Ocean project funding for A-TWAIN. Two moorings were deployed by the Institute of Oceanology, Polish Academy of Science (IOPAS), and four by Woods Hole Oceanographic Institution (WHOI), USA. The latter were deployed to obtain a first coverage of the outer branch of the Atlantic Water current, and had funding for only one year. Three A-TWAIN moorings were redeployed in 2013, along with one from IOPAS. Together these moorings will cover the innermost Atlantic Water branch also in the coming year. We hope to continue this data collection in the future, as it is the only data series covering the actual inflow of Atlantic Water into the Arctic Ocean via Fram Strait – the warmer of the two main pathways.

Profiles

To complement and fill in the spatial gaps between the mooring locations, we collected a substantial number of vertical profiles of hydrography and current, and took water samples for analysis of a much broader set of biological and biogeochemical parameters. This was done both during the first deployment cruise in September 2012 and during the recovery and redeployment cruise in autumn 2013, where six institutes participated (UiT – Arctic University of Norway, Institute of Marine Research, Norwegian Polar Institute, University of Bergen, IOPAS, and WHOI).

Forecast

We are currently processing the data from the first year-long series and from the cruises. The first joint publications from the project should be published in the coming year. Processed and averaged data will be made publicly available in appropriate databases. We believe that the data will be used both for fundamental research, for operational purposes such as tuning forecast models of ice and ocean, and for evaluation and improvement of climate model performance.

The project was recently presented at the annual meeting of the Forum for Arctic Ocean Modeling and Observational Synthesis, in Woods Hole, USA. The community was enthusiastic about the successful completion of the first year of measurements, and the continuation of the program. Several institutes have since that meeting indicated their intentions of becoming partners by providing instrumentation and personnel for cruises from next year.

Data

The data will be used for evaluating simulation performance of the sea ice-ocean-ecosystem model established within the Fram Centre Arctic Ocean flagship project Modeling of ice, ocean and ecology of the Arctic Ocean.

This consists of a setup that gives 4 km horizontal resolution for the entire Arctic Ocean and Nordic Seas, and an even finer-resolution model of 800 m which covers the Svalbard area including Fram Strait and the mooring area at 30° East.

The dataset will also be used in the project Carbon Bridge, led by the Arctic University of Norway and funded by the National Research Council’s NRC Polar Program. Carbon Bridge has the A-TWAIN area as its focal point for three cruises in 2014.

The initiative Arctic in Rapid Transition, endorsed by the International Arctic Science Committee, will use the A-TWAIN line as focal point for a cruise with RV Polarstern in 2015. The data will also be useful for understanding the oceanographic conditions during the RV Lance freeze-in drift project which will take place in the first six months of 2015 (see article on page X). Furthermore we aim to use the data in collaboration with the new Nansen and Amundsen Basin Observing System project, run by the International Arctic Research Center, Fairbanks, USA, and the Arctic and Antarctic Research Institute (AARI), St. Petersburg, Russia, and for the Laptev Sea Systems project (Alfred Wegener Institute/AARI).

More information:

The project “Long-term variability and trends in the Atlantic Water inflow region” (A-TWAIN) is led by Vladimir Pavlov of the Norwegian Polar Institute and Randi Ingvaldsen of the Institute of Marine Research, working with colleagues Marit Reigstad (UiT – Arctic University of Norway), Frank Nilsen (University Centre in Svalbard) and others. See more at www.whoi.edu/warmingarctic/. For more information please contact vladimir.pavlov@npolar.no

Read rich illustraded article in Fram Forum 2014

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