Land-ocean coupling in Young Sund (2011-12)
Background and relevance to the GEM Strategy 2011-15
The impact of potentially increasing freshwater discharge from Greenland to the sea is poorly understood. Increased precipitation and glacial melt-water stand to greatly influence coastal but also potentially oceanic ecosystems. The larger supply of freshwater from land to sea will influence hydrography, biogeochemistry, and underwater light environment which in turn combined will change the biological productivity of these waters. Young Sund provides a unique location to study this coupling between land and ocean. Nowhere else do we have the logistical support, the background knowledge, the time series and the detailed information about the quantity of freshwater entering the fjord, including its content of carbon, inorganic particles and nutrients. This project will address these research themes in close collaboration with the newly established Greenland Climate Research Center by capitalizing on the ideal conditions for doing arctic marine research in Young Sund. The participants are thus a mix of specialists bringing knowledge and very sophisticated equipment to Young Sund and scientists with a long-term knowledge of the physical and biological conditions in the fjord.
The proposed project consists of three closely linked components. The central idea is to use the gradient in Young Sund, with its heavy input of glacial melt water in the inner part and more oceanic conditions in the outer part, to study the impacts of freshwater on the marine ecosystem. Studies along this east-west gradient can to some extent also give a hint about conditions in the future, with current conditions in the inner part of the fjord being expected to extend further seaward as the Greenland Ice Sheet continues to melt.
The project has three interrelated components:
A. Physical aspects of water mixing and stratification induced by melt water in the fjord.
New profiling instruments will be used to produce very high resolution profiles of fine scale turbulence in the fjord. Data will be used to identify the physical processes controlling vertical mixing and stratification and thus ultimately the supply of nutrients to the photic zone.
B. Quantification of light conditions with focus on the influence of inorganic particles and dissolved organics.
New optical instruments will be used to describe the light conditions for primary producers in the fjord and quantify how inorganic particles and dissolved organic carbon from land influence the light conditions. The new data will be part of a model for light attenuation in Greenlandic waters being developed as part of a Greenland Climate Research Centre project and will extend the utility of the light data currently collected in the Marine Basis program
C. Primary production of the Subsurface Fluorescence Maximum
In this part of the project we will bring new instruments that allow the activity of the phytoplankton to be assessed through depth profiles. This gives us - for the first time - an opportunity to look at the spatial variation in primary production. New sensors for oxygen, fluorescence and light (PAR) will also be installed on the permanent mooring in the fjord to provide new information of the seasonal dynamics of the phytoplankton.
In addition to the project(s) described above, at least four additional projects (spinoff projects) are interested in supporting the activities described above. These four projects are financed from other sources but are dependent on the data generated by the current project(s).
The four additional projects project focus on: 1) Pelagic-benthic coupling, i.e. the fate of primary production in the water column and how that is transported to the sea bottom. 2) Oxygen dynamics of the sea floor using new in situ instrumentation. 3) Air-sea flux of CO2 using direct flux measurement by eddy correlation techniques (DEFROST). 4) Characterization of Greenland melt water, to help interpretation of tracing freshwater in the East Greenland Current (DSF project NAACOS, with collaboration with Norwegian Polar Institute)