Skip to comments.A CLIMATE SHIFT TO COOLER CONDITIONS?
Posted on 04/30/2003 10:13:58 PM PDT by Mike Darancette
In an important and insightful paper published earlier this year in Science, Chavez et al. (2003) reviewed the physical and biological evidence for climatic fluctuations "with periods of about 50 years that are particularly prominent in the Pacific Ocean," reporting that "instrumental data provide evidence for two full cycles: cool phases from about 1900 to 1925 and 1950 to 1975 and warm phases from about 1925 to 1950 and 1975 to the mid-1990s."
Based upon this cyclical temperature history, Chavez et al. suggest that not only is a climate regime shift to cooler conditions likely sometime soon, it may already be in progress. In reference to the 1976-77 regime shift in the Pacific, for example, they note that "it took well over a decade to determine that a regime shift had occurred in the mid-1970s" and, hence, they suggest that "a regime or climate shift may even be best determined by monitoring marine organisms rather than climate."
So what's their evidence for thinking we may already be in the early stages of a major cool-down? Among other things, Chavez et al. cite "dramatic increases in baitfish (including northern anchovy) and salmon abundance off Oregon and Washington," as well as "increases in zooplankton abundance and changes in community structure from California to Oregon and British Columbia, with dramatic increases in northern or cooler species."
Physical data to complement these biological observations were presented by Freeland et al. (2002), who describe a recent "invasion of subarctic water" in the northern California Current. Subsurface waters in an approximate 100-meter-thick layer located between 30 and 150 meters depth off central Oregon were, in the words of the authors, "unexpectedly cool in July 2002." Specifically, mid-depth temperatures over the outer continental shelf and upper slope were more than 0.5°C colder than the historical summer average for the period 1961-2000. At the most offshore station, in fact, the authors report that "the upper halocline [was] >1°C colder than normal and about 0.5°C colder than any prior observation [our italics]."
Much the same thing was noted along the line that runs from the mouth of Juan de Fuca Strait to Station Papa at 50°N, 145°W in the Gulf of Alaska. There, as they describe it, "conditions in June 2002 [were] well outside the bounds of all previous experience [our italics again]," while in the summer of 2001 conditions were "already at the lower bound of previous experience." Based on these several observations, Freeland et al. concluded that "the waters off Vancouver Island and Oregon in July 2002 were displaced about 500 km south of their normal summer position."
Recent observations on the other side of North America point to a similar invasion of abnormally cold water. In a news item in the 24 April 2003 issue of Nature, Hoag (2003) reports that "more than 700 tonnes of Atlantic cod have frozen to death in chilly waters off eastern Newfoundland." How chilly you ask? Hoag says that in early April "the temperature of the water column in Smith Sound fell to -1.7°C" and that "historical temperature profiles from the region indicate that such temperatures are very unusual for the sound." Indeed, to find a comparable "fish freeze," Hoag had to hearken all the way back to 1882, when millions of warm-water tilefish died off the northeastern coast of the United States.
These remarkable marine water cooling events on both sides of North America draw our attention to what happened to the continent's great inland fresh waters in March of 2003. As reported in our Editorial of 16 April 2003, three of the five Great Lakes -- Superior, Huron and Erie -- all froze over completely. The last time this 100% triple-freeze occurred was, well, never ... at least over the period for which reliable data are available, i.e., 1963 to the present.
Yes, something dramatic is definitely in the works, as we opined at the conclusion of our review of the Freeland et al. paper, where we suggested it could well be a return to cooler conditions in the Pacific. Now we are wondering if it might not be a return to cooler conditions over an even wider area.
References Chavez, F.P., Ryan, J., Lluch-Cota, S.E. and Niquen C., M. 2003. From anchovies to sardines and back: multidecadal change in the Pacific Ocean. Science 299: 217-221.
Freeland, H.J., Gatien, G., Huyer, A. and Smith, R.L. 2002. Cold halocline in the northern California Current: An invasion of subarctic water. Geophysical Research Letters 30: 10.1029/2002GL016663.
Hoag, H. 2003. Atlantic cod meet icy death. Nature 422: 792.
Copyright © 2003. Center for the Study of Carbon Dioxide and Global Change
Thought you might find this interesting.
The one thing predictable about weather is that it changes :O)
Thanks for the heads up.