April 12, 2010

Icing Up the Great Lakes

Congratulations to Boston College and Wisconsin for making it to the finals of the NCAA Men’s Hockey Tournament with Boston College dominating for the national title. College sports fans would generally agree that football is the #1 sport in terms of overall fan interest followed by men’s basketball. Picking the 3rd most popular sport is more difficult with fans in the Great Lakes and New England areas insisting hockey is #3 while fans throughout the Sun Belt insist that baseball is the clear #3. With the focus this week on the hockey finals played in Detroit by schools from the American hockey belt, we turned our attention specifically to the Great Lakes themselves.


Boston College Lovin’ the Ice!

Conduct a web search on “Global Warming and Great Lakes” and over 700,000 websites are located with all the horrible things that will happen as the region, and the lakes, warm due to the ongoing buildup of greenhouse gases. The water levels will drop causing massive problems for shipping, every ecosystem in any way related to the lakes will be in serious trouble, less ice will expose more liquid water to the atmosphere thereby creating incredible snowfalls downwind of the lakes, and on and on. One of the common predictions at nearly every site is that the lakes will see a reduction in ice cover – it is not very difficult to sell the idea that a warmer environment will lead to less ice.

A recent article in Eos, Transactions of the American Geophysical Union caught our eye given its startling title “Severe Ice Cover on Great Lakes During Winter 2008–2009.” We knew right away this one could be good.

The article was produced by a team of six scientists with the National Oceanic and Atmospheric Administration in Michigan as well as the University of Michigan; the work was supported by a National Research Council Fellowship at the National Oceanic and Atmospheric Administration’s Great Lakes Environmental Research Laboratory.

Wang et al. begin noting “The North American Great Lakes contain about 95% of the fresh surface water supply for the United States and 20% for the world. Nearly one eighth of the population of the United States and one third of the population of Canada live within their drainage basins. Because of this concentration of population, the ice cover that forms on the Great Lakes each winter and its year-to-year variability affect the regional economy. Ice cover also affects the lake’s abiotic environment and ecosystems in addition to influencing summer hypoxia, lake effect snow inland, water level variability, and the overall hydrologic cycle of the region”.

The global warming crusade will love to learn that “From the late 1990s to the early 2000s, the volume of lake ice cover was much lower than normal, which enhanced evaporation and led to a significant water level drop, as much as 1.3 meters.” This is it – less ice, more evaporation, lower lake levels – 1,000s of websites make this very prediction given the increase in atmospheric carbon dioxide.

The global warming alarmists are not going to like much else that they read in the Wang et al. article! We find “After a decade of little ice cover, from 1997–1998 to 2007–2008, the Great Lakes experienced extensive ice cover during the 2008–2009 winter. The area of Lake Superior covered by ice during the 2008–2009 winter reached 75,010 square kilometers on 2 March 2009, nearly twice the maximum average of nearly 40,000 square kilometers. By this time, Lake Superior was nearly completely ice covered, as were Lake Huron, Lake Erie, and Lake St. Clair, a small basin between Huron and Erie. Even northern Lake Michigan experienced severe ice cover.” As seen in their figure below, adding 2008-2009 to any time series of ice cover changes the picture entirely.

Let’s have a look at the three plots that appear below the satellite image of the frozen Great Lakes (Figure 1). The winter-season surface air temperatures (shown in red) reveal that the late 1970s were indeed cold in the area – old timers will recall that the severe cold of the mid-to-late 1970s produced the global cooling scare at the time. Otherwise, we see variability in the winter temperatures, but the expected trend upward is hard to find. Furthermore, since the late 1990s, the winter temperatures have declined slightly. The average ice cover (shown in black) shows a decline over the entire period, but the decline was confined to the period from the late 1970s to the late 1990s. Over the last decade, the trend has been toward higher average ice cover. Lastly, we look at the maximum ice cover extent (shown in green) and see a pattern highly correlated with the average ice cover. The trend upward over the past decade is far more pronounced for the maximum ice cover than the average ice cover.


Figure 1. (a) Maximum ice extent in the Great Lakes as pictured by the Moderate Resolution Imaging Spectroradiometer on board NASA’s Terra satellite on 3 March 2009. (b) Time series of maximum ice area (green curve), annual average ice area (black curve), and basin winter average surface air temperature (SAT) (red curve). The zero- lag correlation coefficients between the annual mean and maximum ice areas (r = 0.89), between annual mean ice area and SAT (r = –0.89), and between annual maximum ice area and SAT (r = –0.91) are also shown. (Source: Wang et al., 2010)

Wang et al. comment on these patterns noting “Previous studies show that Great Lakes ice cover had a significant downward trend, about ~1% per year, for the period between the onset of winter in 1972 and the end of winter in 2001. Nevertheless, during the entire period of the winters of 1972–1973 to 2008–2009, the downward trend disappears or even reverses. This indicates that (1) natural variability dominates Great Lakes ice cover and (2) the trend is only useful for the period studied.”

(Note: The current 2009-2010 ice season is a rather sparse one over the Great Lakes, and while the addition of this year’s data may temper these trends somewhat, there is still an upward trend since the late 1990s).

The bulk of the article deals with global scale teleconnections that influence weather and climate all over the world. Wang et al. observe “It is well known that the Great Lakes region can be significantly influenced by the El Niño – Southern Oscillation (ENSO) in the Pacific Ocean, via the Pacific – North America (PNA) pattern, the Arctic Oscillation (AO) or the North Atlantic Oscillation (NAO). Indeed, the teleconnections that led to severe ice cover in the 2008–2009 winter were caused by the combined effects of two phases in the shifting patterns of sea level pressure: an unusual positive AO and a LaNiña phase of ENSO.”

Wang et al. add “The drastic changes in lake ice cover over the past few decades imply that significant natural variability, caused by interactions with remote climate patterns (teleconnections), played a large role in what was observed and overshadowed the simple downward trend of lake ice caused by anthropogenic climate warming.”

This is hardly strong endorsement for the never-ending claims that global warming is quickly melting away the Great Lakes’ winter ice cover. In fact, natural variability seems to be running a power play while global warming sits idly in the penalty box. Bad news perhaps for global warming catastrophists, but good news for college hockey fans who love their world frozen!

Reference:

Wang, B.J., X. Bai, G. Leshkevich, M. Colton, A. Clites, and B. Lorgren. 2010. Severe Ice Cover on Great Lakes During Winter 2008–2009. Eos, Transactions of the American Geophysical Union, 91, 41-52.




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