Holocene glacier and ice cap fluctuations in southwest Greenland inferred from two lake records

QUATERNARY SCIENCE REVIEWS

卷:246

Article

Larocca, Laura J.¹  Axford, Yarrow¹  Woodroffe, Sarah A.²  Lasher, G. Everett^1,3  Gawin, Barbara¹ 

[1] Northwestern Univ, Dept Earth & Planetary Sci, 2145 Sheridan Rd, Evanston, IL 60208 USA

[2] Univ Durham, Dept Geog, Lower Mountjoy South Rd, Durham DH1 3LE, England

[3] Univ Pittsburgh, Dept Geol & Environm Sci, 4107 OHara St, Pittsburgh, PA 15260 USA

关键词: Greenland;    Lake sediments;    Holocene;    Paleoclimate;    Glaciers and ice caps;    Equilibrium-line altitudes;    Isolation basins;   

DOI  :  10.1016/j.quascirev.2020.106529

来源: Elsevier

【 摘 要 】

Glaciers and ice caps (GICs) respond rapidly to changes in temperature and precipitation. Thus, records of their past fluctuations yield valuable information on past climate. However, relatively little is known about the long-term, Holocene history of Greenland's local GICs, peripheral to the Greenland Ice Sheet. Here we report sediment records of Holocene glacier activity from two distally fed glacial lakes near Buksefjord, southwest Greenland. The two lakes' watersheds host modern GICs of contrasting size. The Pers Lake (informal name) watershed drains part (3 km(2)) of a single small ice cap. In contrast, nearby Lake T3's (informal name) watershed drains numerous GICs totaling 100 km(2) . At the time it emerged from the sea similar to 8.6 ka BP, Pers Lake was receiving no glacial meltwater input. Sediment physical and geochemical properties indicate persistent meltwater input and regrowth of the ice cap within the Pers Lake catchment beginning at similar to 1.4 ka BP, after almost 3000 years of sporadic meltwater input beginning similar to 4.3 ka BP. The ice cap above Pers Lake reached a maximum late Holocene extent during the final phase of the Little Ice Age (LIA), similar to 0.1 ka BP. The complementary Lake T3 sediment record suggests continued meltwater input from the larger suite of upstream GICs from the time of the lake's isolation from the sea similar to 8.4-7.5 ka BP through to the present. This indicates that some GICs here probably survived the Holocene Thermal Maximum (HTM), although were significantly reduced in size for an extended period (of unknown age and duration). Combined with evidence from Pers Lake and prior studies that show GICs at low and intermediate elevations in this region melted away completely during the HTM, and evidence for GIC presence at Lake T3, we provide lower and upper bounds on regional HTM equilibrium-line altitudes (ELAs). We estimate that regional ELAs were between similar to 1370 and 1470 m above sea level in the early-to-middle Holocene. From the middle to late Holocene, our results, along with other regional GIC studies, indicate progressive lowering of regional glacier ELAs in response to Neoglacial summer cooling of similar to 2.7 degrees C, assuming no change in precipitation. (C) 2020 Elsevier Ltd. All rights reserved.

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