Marko, M. D. University of Minnesota, mmarko@d.umn.edu
Ralph, E. D. University of Minnesota/LLO, eralph@d.umn.edu
Megard, R. O. University of Minnesota/EEB,

 
EVIDENCE OF A LATE SUMMER UPWELLING IN WESTERN LAKE SUPERIOR
 
Temperature, climatological, and zooplankton data demonstrate an upwelling occurred between August 1st and August 13th, 1997 along the North Shore of Lake Superior. Winds were continuous for 11 days from the north-northwest at 2-6 m/s. Before and after the upwelling, winds were from the south at 2-6 m/s. Surface water temperatures within one kilometer of the coast from Grand Marais, MN to Duluth, MN dropped on average from 14 deg. C to 6 deg. C. The minimum depth of the 4 deg. C isotherm rose from 50 m to 30 m within one km from shore and from 40 to 25 m within 5 km from shore. Both deep and surface water temperatures did not return to pre-upwelling values until August 21st. These upwellings are common in late Summer along the North Shore of Western Lake Superior and affect both the phytoplankton and zooplankton communities. Zooplankton communities were found to change in both species abundances and distributions as determined by net tows and acoustic measurements (at 192 kHz) and could be seen to extend 10 km from the coast.
 
Day: Thursday, Feb. 4
Time: 10:45 - 11:00am
Location: Hilton of Santa Fe
 
Code: SS52TH1045H