Early results from an array across the tidally mixed front on southern Georges Bank

R. Schlitz and K. Smith

A seven element closely-spaced current array centered at the 60 m isobath across the southern flank of Georges Bank was set in March, 1999 and recovered in August, 1999. There were two settings, first from ~20 March to 20 June and second from ~20 June to 1 September. The second setting was moved toward the west about 8 nm due to opening of Closed Area II for scalloping. All moorings in the array were recovered except one tripod which will be returned 8-10 November using a ROV system.

In addition, sampling to examine physical and biological processes in the frontal area was completed on each of three cruises, including CTD, MOCNESS/VPR, and nutrients. On the March cruise there were 23 MOC/VPR tows and 3 CTD sections with nutrients. On the June cruise there were 19 MOC/VPR tows and 8 CTD sections with nutrients. Finally on the August cruise there were 8 MOC/VPR tows and 5 CTD sections with nutrients. MOC/VPR tows were primarily designed to provide a time series at the mean position of the front. CTD/nutrient sections were generally closely-spaced along the array.

Data are presented in the form of a video loop. The three-dimensional structure of currents along the array of current meters during the unstratified season from March-June, 1999 are dominated by high variability. Alongshelf jets have time scales of days and the spatial scale is ~3 km horizontally. There are energetic events in the secondary, i.e. in the across shelf plane, that appear related to the alongshelf structure. There has not yet been any quantitative analyses of these data at this early date.