Sunspots Drive Glacier Movement
Fossilized stumps and chunks of logs left jumbled in rubble reveal that glaciers in British Columbia's Coast Mountains have been anything but static and stable over the last thousand years. In Garibaldi Park, located adjacent to Whistler, about 70 kilometres north of Vancouver BC, these and other clues collected from nine glaciers provide one of the most extensive records ever discovered of ice expansion and retreat.
Colder temperatures beginning sometime after 1000 AD caused the park's glaciers to advance between 1150 and 1270 AD. They then shrunk almost to their present-day size. More advances occurred in the 14th and 15th centuries. The ice cover reached its largest expanse of the last millennium at around 1700 AD. A series of retreats and smaller growth spurts occurred five times in the 19th and early 20th centuries, each advance leaving behind a moraine.
The ice occasionally moved at a pace that was not at all glacial. Helm Glacier galloped forward 380 metres in 62 years during the 1400s. At times, spreading ice tongues mowed down forests that were 250 to 300 years old.
The ebb and flow chronicled for Garibaldi's glaciers coincides with patterns detected in glaciers of the Canadian Rockies, the states of Washington and Alaska, Europe, South America and New Zealand. Ice accumulated when cold climates prevailed and melted when weather warmed.
This synchrony around the world suggests that the climatic fluctuations were on a global scale. Glacier activity seems ultimately driven by the frequency of sunspots, which influences how much solar radiation reaches earth. Expansions of ice in Garibaldi Park took place during periods of few sunspots, specifically AD 1020-1080, 1290-1370, 1460-1550, 1645-1715 and 1795-1825.
Johannes Koch, John J. Clague and Gerald D. Osborn. 2007. Glacier fluctuations during the past millennium in Garibaldi Provincial Park, southern Coast Mountains, British Columbia. Canadian Journal of Earth Sciences. 44(9): 1215-1233.