Alongshore variability over the inner continental shelf observed using fiber-optic distributed temperature sensing

Circulation patterns over the inner continental shelf are spatially complex and highly variable in time. Significant fluxes of water, heat and other tracers may be associated with alongshore variability, especially in regions where the coastline and isobaths are not straight. Under stratified conditions, sustained subsurface observations are needed to characterize three-dimensional patterns of circulation, even in shallow water. To observe multiple scales of alongshore variability, a distributed temperature sensing system (DTS) was deployed within a larger-scale mooring array south of Martha's Vineyard, MA. A fiber-optic cable oriented in the alongshore direction was used to collect bottom temperature measurements with 5 m horizontal resolution, over a distance of 4.9 km. Although temperature gradients are generally stronger in the cross-shelf direction, significant variability is observed in the along-shelf direction. Along the 15 m isobath, rapid cooling events are observed with greater regularity and magnitude at locations closer to irregular bathymetry. The DTS observations show that fronts travel away from this region of strong tidal and bathymetric variability with an alongshore component. Lack of uniformity in magnitude and frequency of cooling events, at sites separated by less than 5 km in the alongshore direction, indicates that alongshore differences are present at short time scales of less than a day. Thus, the characteristics of high-frequency temperature variability at one location are therefore not necessarily representative of other nearby locations along the same isobath.

Raw project data is available by contacting [e-mail]