A geometric model for the Beaufort/Chukchi Sea thermohaline structure

Abstract

A geometric model has been developed for analyzing observed Beaufort/Chukchi Sea temperature and salinity profiles based on their geometric features. It contains four major components: (a) a nonhomogeneous mesh difference scheme for second derivatives partial differential2T(z(k))/partial differentialz2 and partial differential2(z(k))/partial differentialz2 at each data point (Z(k), T(k), S(k)); (b) a set of key depths (depths of mixed layer, upper and lower thermoclines and haloclines, and deep layers) determined mostly by the geometric features of profiles, such as depths of minimum and maximum of partial differential2T(z(k))/partial differentialz2 and partial differential2S(z(k))/partial differentialz2 for shelf water and upper portion deep water; (c) modeled profiles T(z(k)) and S(z(k)), which are linearly interpolated from observed T, S values at the key depths; and (d) statistical tests for accepting [T(z(k)), S(z(k))] as a good representative of (z(k), T(k), S(k)). The output of this geometric model is a set of major characteristics of each profile: sea surface temperature (salinity), mixed layer depth, upper- and lower-thermocline (halocine) depths, thermocline (halocline) temperature (salinity) gradient, and deep layer stratification. Analyzing 3562 Beaufort/Chukchi Sea historical (1970-93) temperature and salinity profiles from the Naval Oceanographic Office's Master Oceanographic Observation Data Set by this geometric model, the Beaufort/Chucki Sea thermohaline field reveals a dual structure: one layer (vertically uniform) on the continental shelf (depth < 150 m) during winter and multiple layers (mixed layer, thermocline/halocline, sublayer) during summer. Strong seasonal variations were also found in mixed layer depth, upper thermocline/halocline depth, and strength.