ARCUS | Arctic Research Consortium of the United States

6th Annual ARCUS Award for Arctic Research Excellence


Submitted by   Aaron Stierle
Authors   Aaron P. Stierle and H. Eicken
Category   Physical Science
Title   Sedimentary inclusions in Alaskan coastal sea ice: Spatial distribution, interannual variability and entrainment requirements
Affiliation   Department of Geology and Geophysics, University of Alaska Fairbanks, Fairbanks, AK, USA

Abstract

We investigated the spatial characteristics of sedimentary inclusions and elucidated processes controlling their spatial and temporal variability in the fast ice cover of the shallow-marine environment of Elson Lagoon near Barrow, AK. This was accomplished by examining the frazil ice layer of sea ice cores representing the 1998, 1999 and 2000 fall freeze-up periods and comparing the results with a sediment resuspension model. Sediments occurred exclusively as aggregates of clay to fine-silt sized particles that were confined to brine inclusions in the frazil ice. The average cross-sectional area of these aggregates was positively correlated with sediment concentration of the frazil ice (R2=0.82, P<0.01). The minimum distance between aggregates was also positively correlated with sediment concentration (R2=0.78, P<0.01). However, there was little correlation between the number of aggregates and sediment concentration. Sediment concentrations ranged from 24 mg/l to 1470 mg/l and sediment loads ranged from 2 g/m2 to 384 g/m2, with 1998 and 2000 sediment loads being one to two orders of magnitude smaller than 1999 sediment loads. We modeled the potential for bottom-sediment resuspension, and found it greater in 1999 than in 1998 and 2000 by more than a factor of two, consistent with the higher sediment loads observed in 1999. Resuspension potential was controlled spatially by the local bathymetry and interannually by wind speed and fetch. At small scales, increases in bottom sediment resuspension resulted in greater sea-ice sediment concentrations, larger aggregates and smaller minimum inter-particle distances.