Influences of Weather and Surface Variability on Sensible Heat Fluxes in Terra Nova Bay, Antarctica

Schick, Kelly E.

Graduate Thesis Or Dissertation

Influences of Weather and Surface Variability on Sensible Heat Fluxes in Terra Nova Bay, Antarctica Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/m613mx873

Abstract

Terra Nova Bay is home to a persistent polynya generated by frequent and intense wind events. Understanding atmospheric processes that influence the sensible heat flux in this region is key to understanding the contribution of the Terra Nova Bay polynya to regional ice production and ultimately Antarctic deep water formation. Automatic weather station (AWS) wind speed and temperature data from Inexpressible Island and surface temperature information is obtained from MODIS Aqua satellite observations over the polynya for the winter season (April to September). Wind speed and temperature data from the years 2003, 2005 and 2012-2017 are used to estimate sensible heat fluxes in Terra Nova Bay using the Coupled Ocean Atmosphere Response (COARE) bulk flux algorithm. Calculated sensible heat fluxes are compared to the input variables of air- surface temperature difference, wind speed, air temperature and surface temperature using rank correlation (ρ). The air−surface temperature difference (ρ =−0.80) and the wind speed (ρ =0.67) explain a moderate amount of the variance in sensible heat flux with air and surface temperature explaining slightly less (ρ =−0.41 and ρ = 0.53 respectively). To examine the influence of changing downwind conditions, sensible heat fluxes are then calculated at 10, 20 and 30 km downwind. In order to best modify the AWS observations to correspond with the downwind distances, gradients of air temperature and wind speed are calculated using Unmanned Aerial System (UAS) observations made over Terra Nova Bay in September 2009 and 2012. The resulting average hourly upward heat flux decreases from 457.8 W m^-2 at the coast to 163.6 W m^-2 30 km downwind. Monthly mean sensible heat flux varies from 328.9 W m^-2 in September to 511 W m^-2 in August. The incidence of statically unstable conditions decreases over that same distance from 89% to 78%. Hourly sensible heat fluxes were used to estimate hourly ice growth rates which decrease from 0.8 cm h^-1 near the coast to 0.3 cm h^-1 30 km downwind. These hourly rates convert to seasonal ice growth estimates of 30 m near the coast and 9m 30 km downwind from the coast.

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