Glacier fluctuations in the northern Patagonian Andes (44°S) imply wind-modulated interhemispheric in-phase climate shifts during Termination 1

Abstract

The Last Glacial Termination (T1) featured major changes in global circulation systems that led to a shift from glacial to interglacial climate. While polar ice cores attest to an antiphased thermal pattern at millennial timescales, recent well-dated moraine records from both hemispheres suggest in-phase fluctuations in glaciers through T1, which is inconsistent with the bipolar see-saw paradigm. Here, we present a glacier chronology based on 30 new ¹⁰Be surface exposure ages from well-preserved moraines in the Lago Palena/General Vintter basin in northern Patagonia (~ 44°S). We find that the main glacier lobe underwent profound retreat after 19.7 ± 0.7 ka. This recessional trend led to the individualization of the Cerro Riñón glacier by ~ 16.3 ka, which underwent minor readvances at 15.9 ± 0.5 ka during Heinrich Stadial 1, during the Antarctic Cold Reversal with successive maxima at 13.5 ± 0.4, 13.1 ± 0.4, and 13.1 ± 0.5 ka, and a minor culmination at 12.5 ± 0.4 ka during Younger Dryas time. We conclude that fluctuations of Patagonian glaciers during T1 were controlled primarily by climate anomalies brought by shifts in the Southern Westerly Winds (SWW) locus. We posit that the global covariation of mountain glaciers during T1 was linked to variations in atmospheric CO₂ (atmCO₂) promoted by the interplay of the SWW-Southern Ocean system at millennial timescales.

Figure 1

Glacial geomorphology and chronology of the (a) Lago Palena/General Vintter ice lobe with ¹⁰Be ages (n = 4) obtained from the innermost moraine ridge (PV6) and (b) the Cerro Riñón valley glacier with ¹⁰Be ages (n = 26) obtained from CR1-CR5 moraine complexes and the additional perched boulder. On top of the boxes the mean moraine age is acompanied by 1 standard deviation (σ) and the Standard Error of the Mean (SEM) including a 3% propagated production rate error (Table 1). Individual ages are presented along with internal uncertainty and sample ID. One age in red italics is considered an outlier. Inset maps with the location of sites mentioned in the text. Black dots correspond with glacial chronologies from RG: Río Guanaco; SUE: Seno Última Esperanza. Red dots correspond to paleovegetation reconstruction. LL: Lago Lepué. CP: Canal de la Puntilla. HM: Huelmo mire. Green dot is the location of ODP1233 sediments core. White outlines represent Northern (NPI) and Southern (SPI) Patagonian Icefields and Cordillera Darwin Icefield (CDI). This figure was created on ESRI ArcGIS v10.4 software (www.esri.com).

Figure 2

Glacier chronology of the Lago Palena/General Vintter basin and selected species from Canal de la Puntilla and Huelmo mire from the Chilean Lake District (CLD) and Lago Lepué pollen record from Isla Grande de Chiloé (IGC). Blue bars highlight pollen-based cold/wet intervals and yellow bars denote pollen-based warm/dry periods within T1.

Figure 3

Paleoclimate proxies spanning T1. (a) Records from the North Greenland Ice Core Project (NGRIP): δ¹⁸O; winter temperatures in purple; summer temperatures in yellow. (b) Glacier length of the Lago Palena/General Vintter ice lobe (this study). Yellow triangles are bracketing radiocarbon ages for the final glacial advance (100% length) of the LGM in the Chilean Lake District. (c) Glacier-derived temperatures from Rakaia Valley, New Zealand^,. (d) Planktonic δ¹⁸O from marine core ODP-1233. (e) Opal flux from marine core TN057-13PC. (f) Integrated δ¹³C from Talos Dome (TALDICE) and EPICA Dome C (EDC). (g) Records from the central West Antarctica Ice Core (WAIS): CO₂ in light blue and δ¹⁸O in red. Blue bars highlight cold/wet intervals and yellow bars denote warm/dry periods inferred from palynological analyses.