Non-invasive, Highly Resolved Observations of Sea-ice Biomass Dynamics: A Link Between Biogeochemistry and Climate

Christopher Krembs1, Klaus Meiners2, Dale Winebrenner3

1Polar Science Center, University of Washington, 1013 NE 40th Street, Seattle, WA, 98105-6698, USA, Phone 206 6850272, Fax 206-616-3142, ckrembs@apl.washington.edu

2Department of Geology and Geophysics, Yale University, Box 208109, New Haven, CT, 06520-8109, USA, Phone 203-432-6616 , Fax 203-432-3134 , klaus.meiners@yale.edu

3Polar Science Center, University of Washington, 1013 NE 40th Street, Seattle, WA, 98105-6698, USA, Phone 206-543-1393, Fax 206-616-3142, dpw@apl.washington.edu

Climatic changes in high latitudes sensitively affect the persistence and dynamic of sea ice. Covering around 12 million square km, sea ice constitutes an ecologically important, transient interface between the atmosphere and the polar ocean. The build up of autotrophic biomass inside sea ice commences early in the season in response to the availability of light and nutrients, at a time when productivity in the water is typically low. Its release constitutes a concentrated pulse of energy to winter starved organisms and increases the vertical organic carbon flux. Sea ice primary productivity estimates range between 30% and 50% of the Arctic marine primary production. Biomass estimates are, however, based on invasive, scattered ice-core observations of low vertically resolution in particular across the ice water interface.

A thin pronounced layer of algae at the sea ice-water interface spatially occurs where fluctuations of sea-ice mass, energy transfer and phase transitions are greatest. Due to the extremely transient nature of the ice water interface, highly temporally resolved data are needed to assess the significance of event-driven export processes from the ice. The vulnerability of sea-ice biomass to temperature anomalies is amplified by melt-water runoff and exposure to the water column. Pelagic populations of grazers respond sensitively to the timing, availability and distribution of food, such as algae micro-layers at the bottom of the ice. Current field methods lack the resolution to understand the causal relations of short-term sea-ice export events and resulting population fluctuations. Sediment traps allow integrated information over time and water volumes but do not reflect ambient food concentrations at the ice water interface and hence lack the sensitivity to resolve event driven deviations from annual means, which matter in the survival of species.

We describe the seasonal in situ evolution of autotrophic biomass along highly spatially resolved vertical profiles in and across the ice water-interface, by means of a new in situ fluorescence system inside fast-ice of the Chukchi Sea during a 7 month deployment. Algae growth commenced very early (January) with distinct colonization patterns leading to a biomass peak at the end of April and export to the water.

Our in situ system illustrates the advantages of a non-intrusive approach in describing the response of biomass to climatic disturbances at the ice-water interface. These achievements lay the foundation of an autonomous biological sea-ice buoy information system which integrates with existing Arctic climatic and physical sea-ice recording systems allowing a investigation of feedback mechanisms between Arctic climate, marine food webs, and biogeochemical fluxes directly below sea ice.

 

Abstract Categories: Biological Feedbac