Abstract
AbstractArctic sea ice incorporates and transports sediment, releasing it back into the water column during the melting season. This process constitutes an important aspect of marine sediment transport and biogeochemical cycling. Sediment incorporation into sea ice is considered to occur mainly through underwater interaction between frazil ice and resuspended sediment, referred to as suspension freezing. However, harsh environmental conditions have greatly limited field observations of this phenomenon. Analysis of mooring data from a coastal polynya in the northeastern Chukchi Sea, in conjunction with coastal ice radar and meteorological data, indicates that suspension freezing is a key mechanism for sediment entrainment into sea ice. During polynya episodes, acoustic backscatter data obtained by an Acoustic Doppler Current Profiler showed the presence of frazil ice from the surface down to 20‐ to 25‐m depth, coinciding with in situ and potential supercooling. Underwater frazil ice persisted over 1 week under windy, turbulent water column conditions. A combination of the turbidity and Acoustic Doppler Current Profiler backscatter data revealed upward sediment dispersion associated with strong currents during the polynya episodes. The fact that frazil ice and resuspended sediment were detected at the same depth and time strongly suggests the interaction between ice crystals and sediment particles, that is, suspension freezing.
Highlights
All Rights Reserved.Sediment‐laden sea ice, referred to as dirty ice, is a common occurrence throughout coastal and offshore regions in the Arctic Ocean (Darby et al, 2011; Eicken et al, 1997, 2005, 2000; Nürnberg et al, 1994; Osterkamp & Gosink, 1984)
On 30 December, 8, 10, 11, 12, and 14 January, frazil ice was detected by the ADCP down to bin 1 (32–33 m), but optical turbidity obtained by the turbidity sensor was not enhanced (Figures 3d and 3f)
This study examines the process of sediment incorporation into sea ice based on the mooring data obtained in a coastal polynya in the northeastern Chukchi Sea
Summary
Sediment‐laden sea ice, referred to as dirty ice, is a common occurrence throughout coastal and offshore regions in the Arctic Ocean (Darby et al, 2011; Eicken et al, 1997, 2005, 2000; Nürnberg et al, 1994; Osterkamp & Gosink, 1984). Sediment incorporated into sea ice is transported with ice drift and released into the ocean during ice melt. These processes contribute significantly to sediment deposition and redistribution, dispersal of pollutants, and transport of organic carbon (Cooper et al, 1998; Eicken et al, 2005; Pfirman et al, 1995; Sakamoto et al, 2005). In sea ice regions, massive phytoplankton blooms have been found to occur during
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