Abstract
Abstract. Glaciers are frequently used as indicators of climate change. However, the link between past glacier fluctuations and climate variability is still highly debated. Here, we investigate the mid- to late-Holocene fluctuations of Gualas Glacier, one of the northernmost outlet glaciers of the Northern Patagonian Icefield, using a multi-proxy sedimentological and geochemical analysis of a 15 m long fjord sediment core from Golfo Elefantes, Chile, and historical documents from early Spanish explorers. Our results show that the core can be sub-divided into three main lithological units that were deposited under very different hydrodynamic conditions. Between 5400 and 4180 cal yr BP and after 750 cal yr BP, sedimentation in Golfo Elefantes was characterized by the rapid deposition of fine silt, most likely transported by fluvio-glacial processes. By contrast, the sediment deposited between 4130 and 850 cal yr BP is composed of poorly sorted sand that is free of shells. This interval is particularly marked by high magnetic susceptibility values and Zr concentrations, and likely reflects a major advance of Gualas glacier towards Golfo Elefantes during the Neoglaciation. Several thin silt layers observed in the upper part of the core are interpreted as secondary fluctuations of Gualas glacier during the Little Ice Age, in agreement with historical and dendrochronological data. Our interpretation of the Golfo Elefantes glaciomarine sediment record in terms of fluctuations of Gualas glacier is in excellent agreement with the glacier chronology proposed for the Southern Patagonian Icefield, which is based on terrestrial (moraine) deposits. By comparing our results with independent proxy records of precipitation and sea surface temperature, we suggest that the fluctuations of Gualas glacier during the last 5400 yr were mainly driven by changes in precipitation in the North Patagonian Andes.
Highlights
Understanding the response of terrestrial environments to past changes in climate is a fundamental aspect of paleoclimate research
Our results demonstrate that the Aniya-type chronology of glacier fluctuations, which was constructed from minimal radiocarbon ages obtained on SPI moraines, is valid for the western side of the NPI
Our results are consistent with a main advance of Gualas glacier at 4180–850 cal yr BP, which can be subdivided into three secondary advance/retreat cycles, as well as three short-term variations between 1750 and 1935 AD
Summary
Understanding the response of terrestrial environments to past changes in climate is a fundamental aspect of paleoclimate research. In this respect, very little is known about the Holocene fluctuations of the outlet glaciers of the Northern Patagonian Ice Field (NPI) and their climatic causes. Glacier fluctuations are frequently used as indicators of climate changes, the individual roles of the different climatic parameters that affect their mass balance (i.e. precipitation, temperature) remain highly debated. In Patagonia there is considerable evidence that glaciers and icefields have expanded and contracted during the Holocene. Most of the evidence comes from outlet glaciers of the Southern Patagonian Icefield (SPI; Glasser et al, 2004). Most authors have focused on quantifying changes in glacier length and area during recent decades (Aniya, 1992; Rivera et al, 2007; Lopez et al, 2010), or on dendrochronological records of moraines and trimlines formed during the last two centuries
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