Late Pleistocene and Holocene palaeoclimate and glacier fluctuations in Patagonia

Abstract

This paper presents the evidence for Late Pleistocene and Holocene palaeoclimate and glacier fluctuations of the two major icefields in Patagonia, the Hielo Patagónico Norte (47°00′S, 73°39′W) and the Hielo Patagónico Sur (between 48°50′S and 51°30′S). The palaeoenvironmental evidence suggests that glaciers still covered large areas of Patagonia at approximately 14,600 14C years BP. Uniform and rapid warming took place after 13,000 14C years BP, with no unequivocal evidence for climate fluctuations equivalent to those of the Northern Hemisphere Younger Dryas cooling event (the Younger Dryas Chronozone, dated to 11,000–10,000 14C years BP (12,700–11,500 cal. years BP). During the early Holocene (10,000–5000 14C years BP) atmospheric temperatures east of the Andes were about 2 °C above modern values in the period 8500–6500 14C years BP. The period between 6000 and 3600 14C years BP appears to have been colder and wetter than present, followed by an arid phase from 3600 to 3000 14C years BP. From 3000 14C years BP to the present, there is evidence of a cold phase, with relatively high precipitation. West of the Andes, the available evidence points to periods of drier than present conditions between 9400–6300 and 2400–1600 14C years BP. Holocene glacier advances in Patagonia began around 5000 14C years BP, coincident with a strong climatic cooling around this time (the Neoglacial interval). Glacier advances can be assigned to one of three time periods following a ‘Mercer-type’ chronology, or one of four time periods following an ‘Aniya-type’ chronology. The ‘Mercer-type’ chronology has glacier advances 4700–4200 14C years BP; 2700–2000 14C years BP and during the Little Ice Age. The ‘Aniya-type’ chronology has glacier advances at 3600 14C years BP, 2300 14C years BP, 1600–1400 14C years BP and during the Little Ice Age. These chronologies are best regarded as broad regional trends, since there are also dated examples of glacier advances outside these time periods. Possible explanations for the observed patterns of glacier fluctuations in Patagonia include changes related to the internal characteristics of the icefields, changes in the extent of Antarctic sea-ice cover, atmospheric/oceanic coupling-induced climate variability, systematic changes in synoptic conditions and short-term variations in atmospheric temperature and precipitation.