Sea Surface Height Variability in Drake Passage
[19-Nov-2015] Donohue, K.A., Watts, D.R., and Kennelly, M. .
Presented at the 2015 Aquarius/SAC-D Science Team Meeting
The cDrake experiment (2007-2011) studied the Antarctic Circumpolar Current using an array of current and pressure recording inverted echo sounders (CPIES). The array consisted of a transport line spanning Drake Passage and a local dynamics array, centered on the eddy kinetic energy maximum. Monitoring and analysis of long-term variability will likely utilize satellite altimeter products; the cDrake data set offers a unique opportunity to examine the constituents of sea surface height variability (SSHA) and compare altimetry with in situ measurements. The CPIES SSHA barotropic contribution varied between 19% and 72% of the total variance. High-frequency signals (HF), above the 1/20 cpd Nyquist frequency of Jason-2, are not a large part of the total SSHA variance, exceeding 18% of the total variance only at handful of sites. The AVISO HF correction significantly underestimates the signal. Moreover, for most of the sites, HF steric SSHA dominates the signal. The fraction of aliased energy, for most sites, is less than 25% for frequencies longer than 1/50 cpd. Measured and AVISO mapped SSHA compare favorably, especially in regions of high SSH variance. Low correlations are found along the northern boundary and at southern sites, south of the Shackleton Fracture Zone where SSH variance is relatively low.