Glacial recession in northern Patagonia during HS1 and HS0 stadial

SOTERES, RODRIGO L.; SAGREDO, ESTEBAN; KAPLAN, MICHAEL; MATEO MARTINI; PABLO UGALDE; REYNHOUT, SCOTT; SCHAEFER, J.M.

Congreso; Actas del Séptimo Congreso Argentino de Cuaternario y Geomorfología; 2018

For morethan two decades, it has been recognized that the overall warming patternobserved in both Polar hemispheres during the Last Glacial-InterglacialTransition (LGIT: ~18 - ~11.7 ka: thousands of years BP) followed a steppedsequence. In Antarctica, the warming tendency was interrupted between ~14.5 and~12.9 Ka by the so-called Antarctic Cold Reversal (ACR). While Greenlandreturned to quasiglacial conditions during two stages, the Heinrich Stadial 1(HS1) between ~18 and ~15 ka and, the Heinrich Stadial 0 (HS0) between ~12.9and ~11.7 ka.In SouthAmerica, recent transient paleoclimate simulation and pollen analysis suggestthat the Antarctic deglaciation signature reached areas as far north as 41°S.However, the northernmost reconstruction of glacial fluctuations during this period only reaches47.5° S, precluding the identification of the deglaciation signature of theregion.Decipheringthe chronology of glacial 􀁅luctuations in northern Patagonia provides anopportunity to assess the interhemispheric phasing of millennial climate eventsoccurred during the LGIT. Determining the sequence of past abrupt climate eventin both hemispheres will contribute to identify internal forcings during globalclimate reorganizations. Here, wepresent new geomorphic and chronological data from a tributary glacier of the Palena/GeneralVintter glacial lobe (43.5° S), in Northern Patagonia. Twenty-five new cosmogenic 10Be exposure ages from the Nikkita valley provide a comprehensive glacialrecord of the mid-latitudes of South America, which constrain the timing andspatial extent of glacial fluctuations during the last deglaciation, allowingus to differentiate the pattern between polar signatures. Ourrecord from Nikkita valley indicates that the ice withdrew to a nearpresent-day limit before ~16.1±0.8 ka. Then, Nikkita glacier readvanced at 13.6±0.6ka during the ACR. Two additional inboard moraine complexes exhibitstatistically undistinguishable ages, indicating repeated glacier expansions duringthis event. Finally, ice retreated to the headwalls of the Andes after a minorglacial pulse at 12.5±0.2 ka.Our findings indicate that the footprint of theAntarctica climate signature reached at least ~43.5°. Glaciers in NorthernPatagonia withdrew signi􀁅icantly during both North Atlantic HS1 and HS0cooling, interrupted by a period of glacial expansion coeval with the ACR. Ourchronology from Nikkita glacier matches glacier records from New Zealand (43°S),suggesting a uniform glacier-climate response to the Antarctic deglacialsignature across the southern mid-latitudes.