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Under-ice observations of water column temperature, salinity and spring phytoplankton dynamics: Eastern Bering Sea shelf

P. J. Stabeno,1 J. D. Schumacher,1 R. F. Davis2 and J. M. Napp3

1NOAA, Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE, Seattle, Washington  98115
2Department of Oceanography, Dalhousie University, Nova Scotia, Canada
3NOAA, Alaska Fisheries Science Center, 7600 Sand Point Way NE, Seattle  98115

Journal of Marine Research, 56, 239–255, 1998.
This paper is not subject to U.S. copyright. Published in 1998 by the Journal of Marine Research


The inundation of two moored platforms by sea ice in late winter and early spring of 1995 provided unique time series of water column temperature, salinity, estimated chlorophyll-a, and phytoplankton fluorescence under advancing and retreating sea ice. One platform was located at 72 m in the weakly advective middle shelf regime. Here, chlorophyll-a concentrations began increasing shortly after the arrival of the ice (March) during the period of weak stratification and continued to increase while wind actively mixed the water column to > 60 m. Changes in water column structure and properties resulted from an event of strong advection rather than vertical fluxes. During winter, such advective events can replenish the nutrients required to support the rich blooms that occur over the middle shelf during spring. The advancing ice was associated with the coldest waters and a deep (>50 m) mixed layer. The ice melt enhanced the two-layer system previously established by advection. A second mooring was located at the 120 m isobath on the more advective outer shelf. The ice reached this site on April 6, and chlorophyll-a concentrations increased as the sea ice melted. At the third mooring, located on the shelf farther south beyond the range of ice, the spring bloom began on ~May 9.

1. Introduction
2. Background
3. Methods
a. Shipboard measurements
b. Surface moorings
c. Acoustic Doppler Current Profiler
d. Winds
4. Results
a. Ice
b. Shipboard Measurements
c. Middle Shelf: Mooring 2
d. Outer Shelf: Mooring 3
e. Mixed Layer Depth
5. Conclusions and Acknowledgments

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