Causes and Consequences of Air-Ocean Energy Fluxes During Arctic Freeze-Up

Ola P G Persson, CIRES/University of Colorado, Boulder, CO, United States, Byron Blomquist, University of Colorado at Boulder, Boulder, CO, United States, Sharon Elisabeth Stammerjohn, University of Colorado Boulder, Boulder, CO, United States, Peter Staples Guest, Naval Postgraduate School, Monterey, CA, United States, William Rogers, Naval Research Laboratory, Stennis Space Center, MS, United States, Chris W Fairall, NOAA/ESRL/PSD, CO, United States, James M Thomson, Applied Physics Laboratory University of Washington, Seattle, WA, United States and Stephen F Ackley, University of Texas at San Antonio, San Antonio, TX, United States
Abstract:
This presentation will use atmospheric and ocean mixed-layer observations from three cruises during the past two years to examine the magnitude and variability of the air-ocean energy fluxes, the sources of the variability, the impact of the fluxes on the ocean mixed-layer thermal structure, and how these surface energy fluxes impact the initial ice formation. The measurements were made during the ACSE, Mirai, and Sea State field programs, the first two obtaining measurements near the ice edge in the Laptev and Chukchi Seas in September 2014 and the last along the advancing ice edge in the Beaufort/Chukchi Sea in October 2015. These time periods include the onset of continuous ocean heat loss, the initial episodic ice formation, and the core period for southward advance of the ice. Frequent atmospheric soundings and continuous remote-sensor measurements provide the vertical kinematic and thermodynamic structure in the lower troposphere. Broadband radiometers, turbulent flux sensors, surface temperature sensors, surface characterization instruments, and basic meteorological instrumentation provide continuous measurements of all surface energy flux terms (shortwave/longwave radiation, sensible/latent turbulent heat fluxes), allowing the quantification of the total energy exchange between the ocean and the atmosphere. Furthermore, each cruise provided continuous measurements of the upper-ocean temperature and salinity and frequent CTD measurements of the ocean temperature and salinity profiles, providing estimates of upper-ocean energy evolution. Various methods for characterizing the ocean surface (open ocean, ice cover, ice thickness, wave state, etc.) allow linking energy changes with changes in ocean surface conditions.

Initial analyses of the September conditions show persistent ocean heat loss after Sep. 15 because of the reduction of downwelling shortwave radiation and impacts of off-ice airflow on turbulent heat fluxes and downwelling longwave radiation. Associated ocean thermal changes occurred primarily in the upper few meters, with temperatures reaching the freezing point in the top 4-10 m at the same time as substantial pancake ice forms on the ocean surface. The presentation will provide further surface energy-flux and process-interaction analyses from all three cruises.

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