Drifter Event G During late June 1999, a large Gulf Stream warm-core ring was located southeast of Georges Bank, centered near 40.8N, 65W. As this ring moved southwest along the southern flank of the bank, AVHRR imagery shows the ring begin to pull off cooler shelf water, forming a large clockwise streamer of shelf water around the northeastern half of the ring (Figure G1). During the first half of July, several drifters deployed on the bank were entrained in the developing streamer. The wind stress on the bank during late June through July was generally weak (less than 0.05- 0.1 N/m^2) and oriented towards the northnortheast (Figure G2). As a result, the drifter motions observed during this period were not noticably influenced by wind-forcing, and provide some insight into the Lagrangian kinematics of streamer formation. In order to investigate the vertical structure of the Lagrangian flow on the bank, some drifters drogued at 40 m were deployed during 1999 along with the standard drifters drogued at 10 m. On June 21, three pairs of 10-m and 40-m drifters were launched in a line across the northern flank near 42.1N, 66.9W (panel 1, Figure G2). These drifters joined six additional 10-m drifters and three 40-m drifters already located on the southern flank. During the next 3-5 days, two of the three 10-m drifters deployed on the northern flank moved quickly (~20-25 cm/s) off the bank to the east and did not return. The remaining 10-m drifter from the northern flank moved more slowly (~9-12 cm/s) south over the next 8 days, turning to the southwest on June 28 between 66.5-67W. The three 40-m drifters moved slightly faster (~13-16 cm/s) towards the southeast over the eastern tip of the bank. During this period, the 10- m drifter near the 60-m isobath continued to move southwest alongbank, and the three 40-m drifters also moved towards the southwest until about June 25-26, when two reversed direction, and the net southwest movement slowed. the two 10-m drifters just inside the the 60-isobth on the southwest corner moved very little. During June 29 - July 4 (panel 2, Figure G1), the three 40-m drifters on the eastern flank turned and moved southwestward. The two shallower drifters moved at similar speeds (~12 cm/s) initially and then slowed on the 4th, while the outermost drifter followed the 100-m isobath at a faster speed (~20 cm/s) until the 4th when it accelerated and turned counterclockwise to the southeast and crossed the 2000-m. One of the three nearby 10-m drifters moved to near the 60-m isobath and moved southwest (~12 cm/s) while the other two moved south across the shelf at similar speeds, with the eastern most reaching the 100-m isobath on the 4th. The three 10-m drifters near the 60-m isobath to the southwest continued to move generally towards the southwest slowly (vector speed ~3-8 cm/s). The three 40-m drifters near 67.6W moved in a complex clockwise pattern, with the more onbank drifter turning south on July 1 and accelerating (to ~35 cm/s) as it moved more southwestward, with the other drifters turning east over the next two days. During July 4 - July 9 (panel 3, Figure G2), one 40-m and two 10-m drifters were carried off the shelf in the streamer near 66.5W. The group of three 40-m drifters initially near 67.6W moved eastward until the 6th when the shallowest drifter turned west, the next drifter turned north, and the deepest drifter continued to accelerate eastward, crossing the 2000-m isobath on the 7th at ~70 cm/s as it entered the streamer. The 10-m drifter near the 60-m isobath near 68.1W turned southeast on the 5th, and moved rapidly to the 100-m isobath and turned east at speeds above 50 cm/s to cross the 2000-m isobath into the streamer on the 9th. The 10-m drifter already near the 100-m isobtah near 66.5W continued to accelerate towards the southeast as it moved into the streamer. The 40-m drifter near the 2000-m isobath on the 4th continued to move southeast and began a small cyclonic path centered near 40.05N, 65.95W. During July 9 - July 19 (panel 4, Figure G2), the one 10-m drifter starting near 40.95N,66.8W moves slowly (~5-10 cm/s) southeast across the upper slope until rapidly accelerating eastward on the 11th. While this 10-m drifter passed within 10 km of a 40-m drifter, the one 10-m and four 40-m drifters remaining on the southern flank continue to move along bank towards the southwest, with all but one of the 40-m drifters eventually turning north through the Great South Channel. The one 40-m drifter caught in a small cyclonic eddy (rough estimate of v/rf ~ 0.3) made two circuits before joining the streamer. The drifter data taken during this streamer formation and warm-core ring entrainment event suggests the following interpretation. Near-surface water may been drawn from as shallow as the 60-m isobath into a streamer, while the source region for subsurface water near 40-m depth appears to be restricted to the outer shelf, perhaps as deep as the 100- m isobath. Several other entrainment events on the southern flank were captured by drifters during the 1995-99 field effort. These events exhibit similar behavior, although none were sampled as well as this July 1999 event. Analysis of hydrographic data collected during the 1983 Warm Core Ring Experiment suggests that the shelf water found in streamers originates over the outer shelf (Schlitz, 2001). Additional measurements are needed to see if the source region for entrained water is such a sharp function of depth. Figure G1. AVHRR image of event. perhaps sequence. Figure G2. Drifter tracks for June 19 - July 19, 1999. Each panel shows drifter tracks over a 10-day or 5-day 5-d period. The 10-m drifter tracks are shown in blue, with a black spot at the head; the 40-m drifter tracks in red, with a black spot at the head. The panel-average wind stress vector is plotted at the center of the bank, with a 0.1 N/m^2 scale vector shown in the upper left for comparison. [use gb_plotG to make figure]