Resolving a persistent offshore surface temperature maximum in Lake Superior using an autonomous underwater glider

Abstract

In November 2009, an autonomous underwater glider (AUG) was deployed for a period of 12 days on the Wisconsin Shelf of Lake Superior. During this period, the AUG made repeated cross-shelf transects from 3 km to 13 km offshore, making 26 cross-shelf transects in all, during which time temperature was measured. Each of these transects displayed a mid-shelf temperature maximum roughly 8 km offshore, with cooler waters both inshore and offshore of this. This is hypothesized to be due to a balance of persistent cooling at the surface and vertical mixing of cooler sub-thermocline waters offshore.