Cascade Lake in southwestern Alaska. The lake is fed by glaciers in the Ahklun Mountains. Glacier meltwater enters the lake on the left in this picture. The amount of sediment delivered to the lake can vary with the intensity of the summer melt season and is registered in sediment cores through changes in depositional rates and other indicators.
Sediment cores were taken as part of a study, supported primarily by the National Science Foundation (NSF), that indicates arctic temperatures suddenly increased during the last 50 years of the period from A.D. 1 to the year 2000. Because this warming occurred abruptly during the 20th century while atmospheric greenhouse gases were accumulating, these findings provide additional evidence that humans are influencing climate.
The study was led by Darrell Kaufman of Northern Arizona University. To learn more, see the NSF press release The Arctic Offers More Evidence of Human Influences on Climate Change. [NSF has supported climate change research in Alaska by Kaufman and his students since 1991. Recent awards include: "Holocene climatic variability in southern Alaska" (grant ATM 03-18341), "Accessing climate and lake monitoring equipment, southern Alaska" (grant EAR 08-20363), "Coupled glacial and lacustrine evidence for decadal- to millennial-scale variability in the climatologic Aleutian Low, southern Alaska" (grant EAR 08-23522), and "A synthesis of the last 2000 years of climatic variability from arctic lakes" (grant ARC 04-55043).]
(Date of Image: July 2004)
Credit: Darrell Kaufman, Northern Arizona University