Thickness of the mixed bottom layer in the Northern Atlantic

Abstract

The thickness of the mixed bottom boundary layer (BBL) has been analyzed based on the CTD data at transoceanic sections in abyssal waters of the Northern Atlantic. The measurements were carried out at two transoceanic sections approximately along 48° N (ASV-99) and 5° N (AI-2000) in 1999 and 2000. These data, and the WOCE data obtained at four zonal sections (AR7E and AR12 along 57° N, AR01 along 24.5° S, and A06 along 7.5° N), were used for the calculation of the statistical characteristics of the BBL’s thickness HB. The probability distribution function F(HB) was close to lognormal. The mean value 〈HB〉 at different latitudes was in the range from 30 to 60 m. The averaged BBL thickness = 46.1 m. The BBL’s thickness was about 1% of the ocean’s depth D; the ratio HB/D was the minimum (0.8%) near the equator and increased up to 1.6% in the polar latitudes.