Abstract
The Magallanes–Tierra del Fuego region, Southern Patagonia (53–56° S) features a plethora of fjords and remote and isolated islands, and hosts several thousand glaciers. The number of investigated glaciers with respect to the multiple Neoglacial advances is based on a few individual studies and is still fragmentary, which complicates the interpretation of the glacial dynamics in the southernmost part of America. Schiaparelli Glacier (54°24′ S, 70°50′ W), located at the western side of the Cordillera Darwin, was selected for tree-ring-based and radiocarbon dating of the glacial deposits. One focus of the study was to address to the potential dating uncertainties that arise by the use of Nothofagus spp. as a pioneer species. A robust analysis of the age–height relationship, missing the pith of the tree (pith offset), and site-specific ecesis time revealed a total uncertainty value of ±5–9 years. Three adjacent terminal moraines were identified, which increasingly tapered towards the glacier, with oldest deposition dates of 1749 ± 5 CE, 1789 ± 5 CE, and 1867 ± 5 CE. Radiocarbon dates of trunks incorporated within the terminal moraine system indicate at least three phases of cumulative glacial activity within the last 2300 years that coincide with the Neoglacial phases of the Southern Patagonian Icefield and adjacent mountain glaciers. The sub-recent trunks revealed the first evidence of a Neoglacial advance between ~600 BCE and 100 CE, which so far has not been substantiated in the Magallanes–Tierra del Fuego region.
Highlights
IntroductionThe subtropical high-pressure system (~35◦ S), leading to prevailing westerly winds by this synoptic constellation [1,2]
The region of Patagonia is situated between the subpolar low pressure trough (~60◦ S)and the subtropical high-pressure system (~35◦ S), leading to prevailing westerly winds by this synoptic constellation [1,2]
The exact dating of the glacial event is influenced by some uncertainties that must be taken into account [39,59,60]: (i) the pith of the tree was not reached or missed during sampling; the number of tree-rings that are lost when the tree is sampled at a distinct elevation above the ground; (iii) the timespan between deglaciation, moraine stabilization, soil development, and the colonization by the first trees; and (iv) the probability that the oldest tree was sampled
Summary
The subtropical high-pressure system (~35◦ S), leading to prevailing westerly winds by this synoptic constellation [1,2]. The mountain range of the Southern Andes forms an obstacle perpendicular to the zonal band of persistent westerlies, resulting in large amounts of precipitation caused by the orographic uplift of humid air masses on the windward side [1,3,4,5]. Though the Pacific Ocean causes moderate temperatures, the vast sum of precipitation nourishes more than 11,000 glaciers south of 45.5◦ S, covering an area of 22,636 ± 905 km in 2016/17 [8] (Figure 1A). While the Andes north of the Strait of Magallanes are striking north–south, the mountain range of the Cordillera (CD) Tierra delDarwin Fuego is(CD) predominantly. In addition to the mountain Darwin range of theon. The amount of precipitation exceeds several thousand millimeter per year [mma−1 ] on the western side, but decreases rapidly towards the east due to the foehn effect, forming one of the worlds sharpest moisture gradients [6,7].
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