Comparison between glider-derived geostrophic velocities and shipboard ADCP measurements

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

On the continental shelf of the west Antarctic Peninsula (WAP), waters below the permanent pycnocline are strongly influenced by intrusions of water masses shed from the Antarctic Circumpolar Current. These intrusions carry relatively warm water toward the coast and to glacier grounding lines, but intrusion locations, mechanisms, and pathways by which this water moves on the shelf are still poorly understood. Dozens of deployments of autonomous underwater vehicles (gliders) in the vicinity of Palmer Deep, a biologically productive canyon on the WAP, have collected temperature and salinity data at extremely high spatial resolution. These data can be used to calculate geostrophic currents in the across-glider-track direction, and this would provide an extensive dataset to study circulation on the WAP shelf, but the relative importance of the geostrophic component to the total current field must first be determined. Here, we present a comparison between one ADCP transect and several repeat glider transects along the same line. Velocities measured by the ADCP are difficult to compare to geostrophic velocities because the shallowest ADCP bin is 46 m below the surface, while geostrophic velocities are referenced to dead-reckoned velocities with a significant contribution from surface currents. Despite limitations, depth-averaged geostrophic currents show promise in being a useful proxy for total depth-average currents on the WAP. The depth-averaged currents from glider deployments show significant day-to-day variability in both magnitude and direction, but the glider transect timed most closely to the ADCP transect showed a similar pattern. Vertical shear is predominantly directed onshore, and measurements of shear below the permanent pycnocline are small compared to those at the surface.

Original languageEnglish (US)
Title of host publicationOCEANS 2016 MTS/IEEE Monterey, OCE 2016
PublisherInstitute of Electrical and Electronics Engineers Inc.
ISBN (Electronic)9781509015375
DOIs
StatePublished - Nov 28 2016
Event2016 OCEANS MTS/IEEE Monterey, OCE 2016 - Monterey, United States
Duration: Sep 19 2016Sep 23 2016

Publication series

NameOCEANS 2016 MTS/IEEE Monterey, OCE 2016

Other

Other2016 OCEANS MTS/IEEE Monterey, OCE 2016
CountryUnited States
CityMonterey
Period9/19/169/23/16

All Science Journal Classification (ASJC) codes

  • Instrumentation
  • Oceanography
  • Ocean Engineering

Keywords

  • Antarctic
  • Geostrophic velocity
  • Glider
  • Thermal wind
  • Vertical shear

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