2000 NOAA/GLERL Milestone Report



PM: Develop better tools, predictive models and understanding related to water quality and coastal ecosystems management

Milestone: Complete the first field year of the 6-year NOAA-NSF Coastal Ocean Program "the Impact of Episodic Events on the Great Lakes" and report results to NOAA-COP, NSF, and on the web (Scientists: B. Eadie and D. Schwab)

Scientists: B. Eadie and D. Schwab; GLERL (734) 741-2281 and 741-2120

NOAA-GLERL, NOAA-Coastal Ocean Program and the National Science Foundation-Coastal Ocean Processes are conducting a jointly funded program to examine the impacts of massive storm events in late winter-early spring on sediment resuspension and transport of particles and associated materials and on subsequent spring ecology in Lake Michigan. This program, Episodic Events: Great Lakes Experiment (EEGLE), is being coordinated by NOAA-GLERL and is scheduled to include a pilot field year, two full field years and two years of subsequent interpretation and product development. We have just completed the pilot and first full field efforts. EEGLE program components include a retrospective analysis of satellite imagery, water intakes, and other historical data, process and survey cruises, moored current meters, traps and data acquisition instruments and coupled hydrodynamic/sediment transport/ecological modeling. There are presently 41 investigators from 17 institutions participating in this interdisciplinary project.

During this pilot year, the program was fortunate to have the opportunity to examine a very large event (figure 1). Only once before, in its 39 years of intake turbidity records, did the St. Joseph water treatment plant (on the southeastern shore of the lake) experience an event of similar magnitude. Although not scheduled to be a full field year, efforts were made to exploit the opportunity of examining this rare event. Cruises were conducted on four different vessels, with activities shown in table 1. A one day Coast Guard helicopter drifter deployment flight was also conducted. While it appears that the winter-spring storms occur annually, there is a large range in scale. As illustrated in figure 1, the 1999 storm event was much smaller than the very large 1998 storm event. The two images of AVHRR reflectance (channel 1 - channel 2) illustrate the approximate maximum of each years' event. A longer-term estimate of the scale of the event is illustrated by the yearly maximum of the 10 day running mean of winter-spring turbidity from the St Joseph, MI Water Treatment Plant. The last bar represents 1999 and shows it to be somewhat below the average. The 1998 bar is similar to 1973 and they are the largest events for this 39 year period. Other water intake (and wind/wave) data are being accumulated for similar long-term evaluations. The relatively small 1999 event allows for an interesting contrast to the large 1998 event. During 1999, we've had successful survey cruises before, during and after the event, along with a number of process cruises. Water sample and Plankton Survey System (PSS) tows will continue on a monthly basis throughout the year. Table 1 shows program activities. There is one more field year, which should be similar in effort to 1999.

Preliminary findings from our efforts include: 1) high particle fluxes associated with the event and synchronized throughout the basin, 2) elevated phosphorus concentrations, low primary production (due to light limitation), elevated heterotrophic rates, elevated Th-234 activity (its use as a tracer looks promising), and elevated PCB concentrations within the plume region. Examination of the meteorological conditions during the storm that generated the March 1998 turbidity plume suggests the existence of a mesoscale atmospheric vortex above southern Lake Michigan coinciding with the generation of the observed eddy. Measured currents and the bulge in the nearshore turbidity pattern are consistent with the hypothesis that longshore convergence in the current field can generate sufficient offshore transport of fine-grained sediments to account for the visible features.

Special sessions have been convened at three international scientific meetings and the program has made an effort to communicate with the interested public via presentations, newspaper articles and radio. In order to promote interdisciplinary activities, the program has held an annual all-hands meeting each fall. The NSF-CoOP Steering Committee, and their invited experts, attended our last meeting in Minneapolis and provided some feedback -- virtually all was positive. For more on EEGLE, please visit our extensive website: www.glerl.noaa.gov/eegle.

Total Days22109166
Water Samples12144294
Plankton Survey Tows-2253
Traps samples12205178
ROV Dives-120253
Current meters-1127
Drifter days-40350
Papers & reports218
Presentations - Public112012
Presentations - Professional2935
Visits to EEGLE web-19,37621,678

Special Sessions at:

EEGLE All-hands meetings (3 day workshops)

Fig 1. Maximum (10 day running average) turbidity at the St Joseph, MI Water Intake (*)