What have we learned from FOSTER-LIS so far?

(Figure above:) Observed flow over a tidal cycle. Currents are averaged vertically using all sampled depths. Six non-sequential crossings were selected, from a period of many days, to nearly uniformly span a 12.4-hour tidal cycle: delay relative to most recent high tide is about (a) 0, (b) 2, (c) 4, (d) 6, (e) 8, (f) 10 hours. Purple-green hatch line is ferry path. Colored lines are constant-depth contours (blue 20m, red 40 m, etc.) to show seafloor depth variation.

(Figure above:) Residual currents are non-tidal net drift, an average over at least several tidal cycles-- in this case, about 2500 ferry crossings spanning two years. Currents in the along-estuary (roughly east-west) direction are shown, more red where directed eastward out of the estuary and more blue where directed westward in to the estuary. Currents shallower than 7 meters deep are not measured by the ferry and have been inferred by assuming the simplest spatial structure and matching total inward and outward flow to conserve volume. An across-estuary vertical slice from Orient Point at left to New London at right is seen, looking westward, with the black vertical line at Plum Island.

(Figure above:) Ferry-observed 2005-2006 seasonal cycle of near-surface temperature, salinity, and chlorophyll concentration, color-coded by position across the sound (blue nearest Orient Point in the south, and red nearest New London to the north; upper legend shows station names as in map). Observations from 2010-2011 (not shown) of temperature and salinity share similar features and also support the conclusions listed below.