Wave impact on surface Lagrangian movement under high wind events: an observation and process model study

Yan Jia, University of Connecticut, Connecticut Institute for Resilience & Climate Adaptation (CIRCA), Groton, CT, United States, James O'Donnell, University of Connecticut, Department of Marine Sciences, Groton, CT, United States, Yaprak Onat, University of Connecticut, Connecticut Institute for Resilience & Climate Adaptation (CIRCA), Groton, United States and Michael M Whitney, University of Connecticut, Marine Sciences, Groton, CT, United States
Abstract:
A westerly front passed over the northern Mid-Atlantic Bight during Aug 6-7, 2018. Buoy observations show that winds were from the southwest and over 9 ms-1 on Aug 6. The next day brought northeast winds at over 13 ms-1. Surface drifters on the inner shelf off Long Island to southern New Jersey shelf break showed consistent ‘reversed C’ trajectories during down-shelf (south and west) movement. The average offshore displacement was ~15 km during Aug 6, with maximum speed ~0.4 ms-1, several times the values observed in weak or no wind conditions. On Aug 7, strong northeast winds brought the drifters back onshore. During this period the significant wave height (SWH) was ~1.6 m at the inner shelf and over 2.1 m at the shelf break. The observations show high SWH continued for 6 hours after the wind speed decreased. For the inner shelf drifter, the time of its maximum speed (>1 ms-1) coincided with the time of the maximum wind speed. However, for the drifter on shelf break, the time of its maximum speed (>1.4 ms-1) occurred after the maximum wind and coincided with the maximum of SWH. This suggests that wave induced Stokes drift may impact the surface Lagrangian movement. We report the results of a process model to estimate the magnitude of the Stokes transport on drifter trajectories to better understand cross-shelf exchange mechanisms.
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