An initial view of subsurface Lagrangian observations in Lake Champlain: General patterns, cross-lake flow and coastal currents

Subsurface free-drifting floats operating in the Main Lake of Lake Champlain in 2002 and 2004 showed the presence of 1) small circular to elliptical motion away from coastal boundaries, 2) linear to curvilinear motion associated with alongshore currents and 3) subsurface westward cross-lake flow located within the base of the epilimnion and upper metalimnion (10–16 m) followed by large displacements up to 48 km by a coastal current. This subsurface westward flow is believed to be driven by linked upwelling and downwelling regimes on either side of the lake. Subsurface moorings deployed for ~ 34 days in 2007 and within 1 km of Whallon Bay's (NY) western shore showed that Kelvin wave dynamics and a high-speed subsurface jet located above the metalimnic core and > 600 m offshore could account for these large southerly transports. This subsurface jet may be linked to the cross-lake flow due to similar vertical positioning. The southern concave shape of Whallon Bay also appears to be the cause of high-speed northward-flowing currents within 400 m of the shore.

► New subsurface Lagrangian floats used in Lake Champlain circulation studies.
► Three circulation systems observed.
► A 6 m thick subsurface cross-lake flow at boundary of epilimnion and metalimnion.
► Cross-lake flow linked with Ekman dynamics.
► Large float displacements indicate Kelvin wave and high-speed subsurface currents.