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Abstract:
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Much of the ongoing discussion regarding synchrony or bipolar asynchrony of paleoclimate events has
centered on the timing and structure of the last glacial termination in the southern mid- latitudes, in
particular the southwestern Patagonian region (50 e55 S). Its location adjacent to the Drake Passage and
near the southern margin of the southern westerly winds (SWW) allows examining the postulated links
between the Southern OceaneSWW coupled system and atmospheric CO2 variations through the last
glacial termination. Results from two sites located in the Última Esperanza area (52 S) allow us to infer
SWW-driven changes in hydrologic balance during this critical time interval. These findings indicate
peatland development under temperate/wet conditions between 14,600 and 14,900 cal yr BP, followed
by cooling and a lake transgressive phase that led to a shallow lake during the early part of the Antarctic
Cold Reversal (ACR, 13,600e14,600 cal yr BP), followed in turn by a deeper lake and modest warming
during Younger Dryas time (YD, w11,800e13,000 cal yr BP), superseded by terrestrialization and forest
expansion at the beginning of the Holocene. We propose that the SWW (i) strengthened and shifted
northward during ACR time causing a precipitation rise in northwestern and southwestern Patagonia
coeval with mid- and high-latitude cooling and a halt in the deglacial atmospheric CO2 rise; (ii) shifted
southward during YD time causing a precipitation decline/increase in NW/SW Patagonia, respectively,
high-latitude warming, and invigorated CO2 release from the Southern Ocean; (iii) became weaker
between w10,000 and 11,500 cal yr BP causing a precipitation decline throughout Patagonia, concurrent
with peak mid- and high-latitude temperatures and atmospheric CO2 concentrations. |