Glacier and terrestrial ecosystem evolution in the Chilotan archipelago sector of northwestern Patagonia since the Last Glacial Termination
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Date
2022
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Abstract
We examine the glacier, terrestrial ecosystem, and climate evolution since the Last Glacial Termination (T1) based on glacial sediments/landform assemblages and palynological data from the Chilotan archipelago (41°30′S-43°30′S), northwestern Patagonia. Deglacial warming drove recession of the Golfo Corcovado glacier lobe from the Last Glacial Maximum moraines in the interior of Isla Grande de Chiloé (IGC) before ∼17.8 ka, along with a rapid and irreversible trend toward arboreal dominance. Subsequent glacier stabilization led to deposition of the innermost moraines in eastern IGC and adjacent islands sometime between ∼17.5–16.9 ka, followed by an acceleration in glacial retreat that vacated the Chilotan Interior Sea in ∼200 years or less. Early successional cold-tolerant shade-intolerant trees prevailed during the initial stages of T1, followed by temperate rainforests dominated by thermophilous shade-tolerant species between ∼15–14.5 ka. A mixed forest with cold-tolerant hygrophilous conifers established between ∼14.5–12.6 ka, implying cooler climate and stronger Southern Westerly Wind (SWW) influence during the Antarctic Cold Reversal. Stand-replacing fires favored early successional shade-intolerant trees, shrubs, and herbs between ∼12.6–10.8 ka in response to milder temperatures and weaker SWW during Younger Dryas time. The early Holocene (∼10.8–7.5 ka) features a maximum in shade-intolerant thermophilous trees, absence of conifers, and peak fire activity, signaling a warm/dry interval with minimum SWW influence. Cooler/wetter conditions have prevailed over the last ∼7500 years driven by strong SWW influence. We conclude that Patagonian glaciers and terrestrial ecosystems responded simultaneously to climate changes at regional, hemispheric, and global scales multiple times since T1. We adhere to the concept that millennial-scale variations in the SWW linked the response of the hydro- bio and cryosphere across the southern mid- and high southern latitudes, and were teleconnected with northern hemisphere events through the atmospheric concentration of greenhouse gases, latitudinal shifts in the Intertropical convergence zone, and deep ocean circulation.
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Glacier, Vegetation and fire history, Northwestern Patagonia, Southern Westerly, Winds, Last Glacial Maximum, Last Glacial Termination, Holocene