The ARCtic Tracer Release EXperiment (ARCTREX): Initial results from the release of passive tracers in the Chukchi Sea.

The initial results of three passive tracer experiments in the Chukchi Sea are presented to characterize and quantify advective processes and diapycnal mixing in the Chukchi Sea. 55 kg of Rhodamine dye was injected in the surface layer of on three occasions, September 10, 2014 (release 1), September 15, 2014(release 2), and September 9, 2015(release 3). The dye was subsequently tracked using a shipboard flow through system and a towed undulating vehicle equipped with Rhodamine fluorometers. Release 1 was carried out in a moderately quiescent, highly stratified region and quickly dispersed throughout the mixed layer to a depth of ~15m. Over the next 3-4 days variability in the patch was characterized by weak advection and mixing by weak (~0.1 PSU) horizontal frontal features that steered and strained the dye patch. In contrast to release 1, a highly energetic region near a strong (1 PSU) frontal feature was chosen for release 2. Release 2 also quickly mixed to 15-20m, then advected north at 30 cm/s. After approximately 4.5 hours it vanished from the surface layer and subducted along downward sloping isohalines. Release 2 was subsequently strained into a thin subsurface layer between the 31 and 31.2 PSU isohalines. It remained subsurface for the next 1.5 days. Release 3 was also injected near a front, albeit less energetic than release 2 and was tracked for 2 days. As in release 1 the dye mixed across a weak persistent front for the duration it was tracked. While the patch advected slowly initially, a wind event strained the dye patch horizontally and quickly advected it to the southwest. The salinity of the dye increased by ~.1 PSU over the course of release 1. These results suggest dispersion due horizontal advection/stirring processes are important in addition to vertical shear processes.