Task 3.5: Carbon Cycling in the Arctic Ocean outflow

Main objective: To investigate carbon cycling and lower trophic level ecosystem functions on the East Greenland shelf to evaluate the physical forcing and sensitivity to climate change for the fate of biogenic matter.
  • Background
    Arctic productivity, biogeochemical cycling and ecosystem functions are tightly coupled to the physical environment and are therefore expected to be very sensitive to climatic changes (Sakshaug, 2004, Wassmann et al., 2004, Olli et al., 2007). The main Arctic productivity takes place on the Arctic shelves and margins and they are also the key sites for the expected changes caused by retreating ice-cover off-shelf, through predicted up-welling along the shelf-breaks and onto the shelves (Carmack and Chapman, 2003). While the inflow shelves, the Chukchi- and Barents Seas, have been subject to large ecosystem and process studies during the past few years through programs like the US initiative SBI (http://sbi.utk.edu/)  and the Norwegian “CABANERA” project (http://www.nfh.uit.no/cabanera) and knowledge about how these inflow shelves function is emerging  (i.e.Grebmeier and Harvey, 2005, Wassmann, 2006) little is known about carbon cycling and ecosystem functioning in the Fram Strait and on the East Greenland shelf. Ecosystem function and partitioning of carbon flow between export production and grazing on the east Greenland shelf has only been investigated in the NEW Polynya and Young Sound (Tremblay et al., in press, Rysgaard and Nielsen, in press.). The impact of  biogenic export from the Arctic Ocean and the composition of and carbon flow through the lower trophic levels in this Arctic Ocean outflow are examples on the basic information lacking in this region. Only through a synoptic field campaign where we start to fill our gaps in knowledge and learn how physical factors regulate the carbon cycling and ecosystem functions, will we be able to investigate consequences of climate change for ecosystems and biogeochemical cycling in this Arctic outflow-shelf ecosystems.

    Major outcome of the task
    The proposed investigation will quantify, comprehend and describe the regulation of the biogenic C flux in order to address the effect of ice cover, biodiversity and food webs out from the Arctic Ocean along the East Greenland coast. The results will improve our understanding of C cycling in Arctic waters by comparison with the well investigated Barents- and Chukchi Shelf Seas and the potential effects of climate change on the Arctic Ocean.  The investigation will also provide validation data for future physical-biological coupled modelling necessary to investigate dynamics and sensitivity of the carbon cycling and ecosystem functioning.

    Proposed activity
    To answer these questions we suggest synoptic investigation strictly coupled to those of physical oceanography. A team of biologists will sample and conduct experiments during an ice drift out of the Arctic Ocean through the Fram Strait (with KV Svalbard, Task 1.8).

    We will carry out investigations of suspended standing stocks of biota (bacteria, phyto-, micro- and mesozooplankton) as well as bio-elements (POC/PON, pigments) and pelagic production through bacterial-, primary- and secondary production (3H, O2, and grazing/egg- /faecal pellet production, respectively). In addition, vertical flux of biogenic matter will be measured at selected stations when 24hrs in situ-sampling is possible. Selected mesozooplankton species will be sampled for studies of population dynamics.

    These data will provide the basis for Task 3.5 aiming to compare the present results with the well investigated Barents Sea shelf to evaluate physical forcing of plankton community composition, production rates and key processes structuring the carbon cycling. Basic research questions are:
    •    Identification of key species, groups and processes for C-cycling in lower trophic levels on the East Greenland shelf
    •    How will processes that regulate C-flow vary on Arctic Ocean in- and outflow shelves?
    •    What is the role of east Greenland shelf for the C-cycling as compared to the better-known Barents Sea shelf?
    •    How much and how is C-cycling influenced by the melting ice exported from the Arctic Ocean?
    All the gathered data will in addition provide validation data for future physical-biological coupled ecosystem modelling, like the existing coupled physical-biological model (SINMOD), validated for the North-Atlantic Margins and the Barents Sea (Slagstad et al., 1999, Wassmann et al., 2006). This model has recently been expanded to include the Fram Strait region and shelf break north of the Barents Sea inside the frame of the NFR supported project CABANERA.

    Links
    Data sampled here will provide validation data for future physical-biological coupled modelling activity. The drift stations with KV Svalbard along the East Greenland shelf will benefit from existing observations and provide additional process- and productivity measurements to the ongoing observation system established by Zackenberg Ecological Research Station and Grønlands Naturinstitutt through close co-operations with responsible for Marin Basis, Prof. Søren Rysgaard (see included letter of support).