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COMPARISON OF OBSERVED AND INDEPENDENTLY-DERIVED UPPER OCEAN CURRENTS AT STATION ALOHA

For studies of oceanic particle transport and ecosystem variability, information about upper-ocean currents is necessary. Long-term in-situ measurements of ocean flow are available at relatively few locations. Two readily available derived current products are the 1/3° Ocean Surface Current Analysis Real-time (OSCAR) and the data-assimilating 1/12° global Hybrid Coordinate Ocean Model (HYCOM) datasets. These products are compared to a 10-year continuous record of high-temporal resolution ocean currents and co-located winds measured by the Woods Hole Hawaii Ocean Time-series Site (WHOTS) mooring at Station ALOHA (22°45’N 158°W). WHOTS ADCP and current meter observations are used to describe the vertical and temporal variability of upper-ocean currents from 2004 – 2014, and reveal surprisingly little vertical variation (< 3 cm s-1) in mean currents from 4 to 105 m depth, and a NW to SW counterclockwise rotation with depth. This, and high correlation (~0.98) between ADCP depth bins in the top 40 m, imply that upper-ocean WHOTS velocity measurements are a useful proxy for surface currents, and may therefore compare well to surface current products. Comparisons of surface velocity between OSCAR and WHOTS, however, yielded correlations below ~0.6, with a sharp drop-off in coherence at periods shorter than ~30 days. Comparisons to HYCOM gave correlations of ~0.5. Unresolved tidal velocities, mapping and assimilation procedures, and altimeter sampling frequencies in the derived products; and mooring motion in the observations may be possible causes of the unfavorable comparisons.

Authors

Rosburg, K. C., University of Hawaii at Manoa, USA, krosburg@hawaii.edu

Potemra, J. T., University of Hawaii at Manoa, USA, jimp@hawaii.edu

Santiago-Mandujano, F., University of Hawaii at Manoa, USA, santiago@hawaii.edu

Lukas, R., University of Hawaii at Manoa, USA, rlukas@hawaii.edu

Weller, R. A., Woods Hole Oceanographic Institution, USA, rweller@whoi.edu

Plueddemann, A. J., Woods Hole Oceanographic Institution, aplueddemann@whoi.edu

Details

Poster presentation

Session #:040
Date: 03/01/2017
Time: 15:30 - 16:30
Location: Poster/Exhibit Hall

Presentation is given by student: No

PosterID: 347