Contrasting precipitation and temperature patterns in the Southern Andes related to the recent shift in the Antarctic Oscillation Index

SRUR, ANA; MASIOKAS, MARIANO; VILLALBA, RICARDO; RIVERA, JUAN; PITTE, P.; ARANEO, DIEGO

Berlín

Conferencia; Conference and Workshop: Climate Impacts on Glaciers and Biosphere in Fuego-Patagonia; 2017

Marked changes in the Antarctic Oscillation Index (SAM) have recently been recorded. Following persistent positive trends since early 2014, an abrupt shift to negative SAM values occurred in October-November 2016 and persisted to early February 2017. Based on the SAM-Marshal Index, January values varied from +3.13 in 2016 to -1.12 in 2017. This contrasting shift provides a good opportunity to determine the temperature and precipitation variations across southern Patagonia associated with SAM phases. We recorded substantial changes in January temperatures between 2016 (warm) and 2017 (cool) over the Andes between 45° and 49°S. At Cochrane, a difference of 3.9°C was recorded between mean January temperatures in 2016 and 2017. Differences were lower to the south (0.6° and 0.2°C at Punta Arenas and Ushuaia, respectively) and in eastern directions, where opposite trends between January 2016 (cool) and 2017 (warm) were recorded at San Julian (-0.4°C) and C. Rivadavia (-0.3°C) on the Atlantic coast. Recorded changes in precipitation were also larger across the southern Andes. Extremely drier conditions in January 2016 contrast with abundant rainfalls during January 2017. On the eastern side of the Southern Patagonian Icefield, rainfall in January 2017 was ten times greater than in January 2016. At C. Masilla and Villa O?Higgins, January rainfalls varied from 5.6 to 110.1mm and 7.9 to 108.3 mm, for January 2016 and 2017, respectively. This rainfall pattern extended north at least to 46°S, where total January precipitations at Balmaceda of 0.2mm in 2016 contrast with 57 mm in 2017. These changes in precipitation decreased comparatively to the south. At Puerto Natales, January precipitation in 2017 (38.2 mm) was approximately three times larger than during the same month in 2016 (12.5 mm) and less than double farther south at Puerto Williams in Tierra del Fuego (51.6 and 90.6 in January 2016 and 2017, respectively). We emphasize the need to document the temperature and precipitation changes related to SAM across southern South America to properly identify the spatial patterns of climate variability associated with this major mode of climate variability at high latitudes in the Southern Hemisphere.