No abstract

We present the first estimate of green snow algae community biomass and distribution along the Antarctic Peninsula. Sentinel 2 imagery supported by two field campaigns revealed 1679 snow algae blooms, seasonally covering 1.95 × 10 6 m 2 and equating to 1.3 × 10 3 tonnes total dry biomass. Ecosystem range is limited to areas with average positive summer temperatures, and distribution strongly influenced by marine nutrient inputs, with 60% of blooms less than 5 km from a penguin colony. A warming Antarctica may lose a majority of the 62% of blooms occupying small, low-lying islands with no high ground for range expansion. However, bloom area and elevation were observed to increase at lower latitudes, suggesting that parallel expansion of bloom area on larger landmasses, close to bird or seal colonies, is likely. This increase is predicted to outweigh biomass lost from small islands, resulting in a net increase in snow algae extent and biomass as the Peninsula warms.

25Southern South America contains a glacial geomorphological record that spans 26 the past million years and has the potential to provide palaeoclimate information 27 for several glacial periods in Earth's history. In central Patagonia, two major 28 outlet glaciers of the former Patagonian Ice Sheet carved deep basins ~50 km 29 wide and extending over 100 km into the Andean plain east of the mountain 30 front. A succession of nested glacial moraines offers the possibility of 31 determining when the ice lobes advanced and whether such advances occurred 32 synchronously. The existing chronology, which was obtained using different 33 methods in each valley, indicates the penultimate moraines differ in age by a full 34 glacial cycle. Here, we test this hypothesis further using a uniform methodology 35 that combines cosmogenic nuclide ages from moraine boulders, moraine cobbles 36 and outwash cobbles. 10 Be concentrations in eighteen outwash cobbles from the 37 Moreno outwash terrace in the Lago Buenos Aires valley yield surface exposure 38 ages of 169-269 ka. We find 10 Be inheritance is low and therefore use the oldest 39 surface cobbles to date the deposit at 260-270 ka, which is indistinguishable 40 from the age obtained in the neighbouring Lago Pueyrredón valley. This 41 suggests a regionally significant glaciation during Marine Isotope Stage 8, and 42 broad interhemispheric synchrony of glacial maxima during the mid to late 43Pleistocene. Finally, we find the dated outwash terrace is 70-100 ka older than 44 the associated moraines. On the basis of geomorphological observations, we 45 suggest this difference can be explained by exhumation of moraine boulders. 46 47 48

The timing and magnitude of glacial advances throughout a glacial cycle can give insight on the underlying drivers of climate change. Our knowledge of glacial activity early in a glacial cycle, however, is limited by incomplete preservation of the geomorphological record. Here, we present a 10 Be-dated glacial chronology from early in the last glacial cycle from the Belgrano valley, east of Monte San Lorenzo in central Patagonia. Our chronology reveals the

The spatial-temporal footprint of millennial-scale climate events during the last glacial-interglacial transition can yield insights into the underlying drivers of climate change, but remains poorly resolved in Patagonia. Here, we assess the glacier response to abrupt cold events and palaeolake evolution using geomorphological mapping along with 10 Be ages and optically stimulated luminescence ages from near Lago Belgrano (47.9 • S) on the eastern side of Monte San Lorenzo. The former Belgrano glacier was sustained by a climatically sensitive ice cap, making the site ideal for investigating the glacier response to abrupt cold reversals. Our data reveal an extensive readvance at 13.1 ± 0.6 ka, consistent with cooling and increased precipitation during the Antarctic Cold Reversal (ACR). Subsequently, ice retreated by