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GLERL 1999 Milestone Reports
GOAL: DOCUMENT, PREDICT, & ASSESS DECADAL-TO-CENTENNIAL CHANGE
OBJECTIVE: Ensure a Long-term Climate Record
PM: Results of 90% of the Research Activities Are to Be Cited in the Year-2000 IPCC Third Assessment of Climate Change.
MILESTONE: The 1998 Laurentian Great Lakes ice cover in historical perspective
Scientists: R.A.
Assel
Purpose
The major goal of this research is to document the anomalous 1998 Great Lakes ice cover and place it in historical perspective relative to the existing ice cover and winter severity climatology. Documentation of the 1998 ice cover is useful in assessing Great Lakes winter climate extremes during the 20th century and providing information useful for assessing climate change during the 20th and 21st centuries. This research thus contributes to our understanding of regional climate variation on decadal-to-centennial time scales.
Efforts
Several collaborators (from: the National Weather Service in
Cleveland, OH., the National Ice Center in Suitland, MD, the
National Center for Environmental Prediction in Silver Spring,
MD, and the GLERL) completed a study to document winter 1997-98
Great Lakes ice cover and winter severity. The annual maximum ice
cover of this benchmark winter is quantified to place it in a
historical perspective. The synoptic atmospheric circulation
pattern associated with the winter weather, winter air
temperatures, and the seasonal progression of ice cover are
documented. Lake-averaged seasonal progression of ice cover is
compared to a 20-winter (1960-1979) normal and to winter 1983
(Fig. 1), one of the strongest El Niño events of this
century. The impacts of this mild winter on U.S. Coast Guard
assistance to shipping during winter, on Great Lakes water
levels, and on some aspects of the winter lake ecology are also
discussed .
Figure 1. Ice concentration for the combined area of the 5 Great Lakes
Customers
Results of this study are of interest to the National Ice Center, the National Snow and Ice Data Center, the United States Coast Guard, the U.S. Army Corps of Engineers, the Canadian Ice Services, the National Weather Service, the Lake Carriers Association (Cleveland, Ohio) as well as to other researchers who consider Great Lakes ice cover and its variation as an important parameter in their studies.
Significance
Winter 1998 has one of the lowest ice covers of the 20th century (Fig. 2). Lower limits were set for annual maximal ice cover over the past 35 winters for several of the Great Lakes. Winter severity for 1998 ranked as one of the mildest over the past two centuries. That winter occurred during one of the strongest El Niño of this century and provides evidence (Assel 1998) that Great Lakes ice cover is generally below normal during extremely strong El Niño events.
Figure 2. Ice Cover near time when combined ice cover for Great Lakes was near its seasonal maximum
Success
Preliminary results of this study were presented at the 79th Annual Meeting of the American Meteorological Society (Assel et al 1999). A more detailed paper has been completed and submitted for journal publication (Assel et al 2000)
Next Steps
We will continue to document anomalous Great Lakes ice covers in the future.
References
Assel, R. A. 1998. The 1997 ENSO event and implications for North American Laurentian Great Lakes Winter Severity and Ice Cover. Jol. Geophysical Research Letters 25(5):1031-1033.
Assel, R..A., J. E. Janowiak, D. C. NORTON, and C. O' Connors. Climate perspective of the 1997-98 Laurentian Great Lakes ice cover. Proceedings, 10th Symposium on Global Change Studies, 79th Annual Meeting of the American Meteorological Society, Dallas, TX, 73-76 (1999).
Assel, R.A. et al., 2000: Laurentian Great Lakes ice and weather conditions for the 1998 El Nino winter. (in review: Bulletin of the American Meteorological Society - July,1999)
Last updated: July 9, 2002 mbl