Time dependent bio-optical and temperature measurements beneath Arctic pack ice

Friday, 19 December 2014
Victoria J Hill, Old Dominion Univ, Norfolk, VA, United States, Michael Steele, Univ Washington, Seattle, WA, United States and Bonnie Light, University of Washington, Seattle, WA, United States
As part of the Arctic Observing Network, a new ice-tethered buoy has been developed for monitoring under-ice light and temperature fields. A 20 to 50 m string supports sensors both within and below the ice for the collection of hourly estimates of vertically resolved downwelling irradiance (412, 443, 555 nm and PAR), temperature, chlorophyll a (Chl a) backscatter, and colored dissolved organic material (CDOM) fluorescence. Two buoys are currently operating. Buoy 1 was deployed in the Beaufort Sea in March 2014 and buoy 2 was deployed at the Barneo ice camp in collaboration with the North Pole Environmental observatory in April 2014.

At both locations, attenuation of light in the uppermost 20 – 50 m of the water column was dominated by CDOM in the early spring. Buoy 1 drifted into the Chukchi Sea in June and experienced a switch from CDOM to phytoplankton dominated absorption. Buoy 2 has continued to drift south, but remains in the central basin. It has moved into water with reduced light attenuation properties, indicating low CDOM and low Chl a concentrations. Both buoys have observed water column temperature increases without associated increases in absorbed energy, indicating proximal open water. These buoys offer a unique opportunity to observe the seasonal evolution of the light field and associated warming of the upper water column in ice-covered seas.