Patagonian and southern South Atlantic view of Holocene climate

SCHAEFER, JOERG; ANDERSON, R. ; SCHWARTZ, ROSEANNE; MATEO MARTINI; STRELIN, JORGE; VANDERGOES, M.; TRAVIS, S.; NIELSEN, S.; KAPLAN, MICHAEL; DENTON, GEORGE; FINKEL, R.; GARCIA, J. L.

QUATERNARY SCIENCE REVIEWS

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2016 vol. 141 p. 112 - 125

0277-3791

We present a comprehensive 10Be chronology for Holocene morainesin the Lago Argentino basin, on the east side of the South Patagonian Icefield.We focus on three different areas, where prior studies show ample glaciermoraine records exist because they were formed by outlet glaciers sensitive toclimate change. The 10Be dated records are from the Lago Pearson,Herminita Península-Brazo Upsala, and Lago Frías areas, which span a distanceof almost 100 km adjacent to the modern Icefield. New 10Be agesshow that expanded glaciers and moraine building events occurred at least at6120 ± 390 (n = 13), 4450 ± 220(n = 7), 1450 or 1410 ± 110 (n = 18),360 ± 30 (n = 5), and 240 ± 20 (n = 8) years ago. Furthermore, other less well-dated glacier expansions of the UpsalaGlacier occurred between ~1400 and ∼1000 and ∼2300 and ∼2000 yearsago. The most extensive glaciers occurred over the interval from ∼6100 to ∼4500 yearsago, and their margins over the last ∼600 years were well within and lower than those in the middle Holocene. The10Be ages agree with 14C-limiting data for the glacierhistories in this area.We then link southern South American, adjacent South Atlantic, and otherSouthern Hemisphere records to elucidate broader regional patterns of climateand their possible causes. In the early Holocene, a far southward position ofthe westerly winds fostered warmth, small Patagonian glaciers, and reduced seaice coverage over the South Atlantic. Although we infer a pronounced southwarddisplacement of the westerlies during the early Holocene, these conditions didnot occur throughout the southern mid-high latitudes, an important exceptionbeing over the southwest Pacific sector. Subsequently, a northward locus and/orexpansion of the winds over the Patagonia-South Atlantic sector promoted thelargest glaciers between ∼6100 and ∼4500 yearsago and greatest sea ice coverage. Over the last few millennia, the SouthPatagonian Icefield has experienced successive century-scale advancessuperimposed on a long-term net decrease in size. Our findings indicate thatglaciers and sea ice in the Patagonian-South Atlantic sector of the SouthernHemisphere did not achieve their largest Holocene extents over the lastmillennium. We conclude that a pattern of more extensive Holocene ice prior tothe last millennium is characteristic of the Southern Hemisphere middlelatitudes, which differs from the glacier history traditionally thought for theNorthern Hemisphere.