An official website of the United States government
Abstract. Determining the timing and extent of Quaternary glaciations around the globe is critical to understanding the drivers behind climate change and glacier fluctuations. Evidence from the southern mid-latitudes indicates that local glacial maxima preceded the global Last Glacial Maximum (LGM), implying that feedbacks in the climate system or ice dynamics played a role beyond the underlying orbital forcings. To shed light on these processes, we investigated the glacial landforms shaped and deposited by the Lago Argentino glacier (50° S), an outlet lobe of the former Patagonian Ice Sheet, in southern Argentina. We mapped geomorphological features on the landscape and dated moraine boulders and outwash sediments using 10Be cosmogenic nuclides and feldspar infrared stimulated luminescence (IRSL) to constrain the chronology of glacial advance and retreat. We report that the Lago Argentino glacier lobe reached more extensive limits prior to the global LGM, advancing during the middle to late Pleistocene between 243–132 ka and during Marine Isotope Stage 3 (MIS 3), culminating at 44.5 ± 8.0 and at 36.6 ± 1.0 ka. Our results indicate that the most extensive advance of the last glacial cycle occurred during MIS 3, and we hypothesize that this was a result of longer and colder winters, as well as increased precipitation delivered by a latitudinal migration of the Southern Westerly Winds belt, highlighting the role of local and regional climate feedbacks in modulating ice mass changes in the southern mid-latitudes.
more »
« less
Midlatitude land surface temperature impacts the timing and structure of glacial maxima: LAND TEMPERATURE IMPACTS GLACIAL MAXIMA
- PAR ID:
- 10030604
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 44
- Issue:
- 2
- ISSN:
- 0094-8276
- Page Range / eLocation ID:
- 984 to 992
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract. We used mapping of bedrock lithology, bedrock fractures, and lake density in Inglefield Land, northwestern Greenland, combined with cosmogenic nuclide (10Be and 26Al) measurements in bedrock surfaces, to investigate glacial erosion and the ice sheet history of the northwestern Greenland Ice Sheet. The pattern of eroded versus weathered bedrock surfaces and other glacial erosion indicators reveal temporally and spatially varying erosion under cold- and warm-based ice. All of the bedrock surfaces that we measured in Inglefield Land contain cosmogenic nuclide inheritance with apparent 10Be ages ranging from 24.9 ± 0.5 to 215.8 ± 7.4 ka. The 26Al/10Be ratios require minimum combined surface burial and exposure histories of ∼ 150 to 2000 kyr. Because our sample sites span a relatively small area that experienced a similar ice sheet history, we attribute differences in nuclide concentrations and ratios to varying erosion during the Quaternary. We show that an ice sheet history with ∼ 900 kyr of exposure and ∼ 1800 kyr of ice cover throughout the Quaternary is consistent with the measured nuclide concentrations in most samples when sample-specific subaerial erosion rates are between 0 and 2 × 10−2 mm yr−1 and subglacial erosion rates are between 0 and 2 × 10−3 mm yr−1. These erosion rates help to characterize Arctic landscape evolution in crystalline bedrock terrains in areas away from focused ice flow.more » « less
