Southern Hemispheric Westerlies control sedimentary processes of Laguna Azul (south-eastern Patagonia, Argentina)

Abstract

Multiproxy investigations of lacustrine sediments from Laguna Azul (52 °S) document multi-millennial Holocene influences of Southern Hemispheric Westerlies (SHW) on the hydroclimatic variability of southeastern Patagonia. During the last 4000 years, this hydroclimatic variability is overprinted by centennial warm/dry periods. A cool/wet period from 11,600-10,100 cal. BP is succeeded by an Early Holocene dry period (10,100-8300 cal. BP) with a shallow lake, strong anoxia, methanogenesis and high salinity. Between 8300 and 4000 cal. BP the influence of SHW weakened, resulting in a freshwater lake considered to be related to less arid conditions. Since 4000 cal. BP, regional temperature decreased accompanied by re-intensification of SHW reaching full strength since 3000 cal. BP. Centred around 2200, 1000 cal. BP and in the 20 th century, Laguna Azul experienced century-long warm/dry spells. Between these dry periods, two pronounced moist periods are suggested to be contemporaneous to the "Dark Age Cold Period" and the "Little Ice Age". Different from millennial SHW variations, centennial fluctuations appear to be synchronous for South America and the Northern Hemisphere. Changes in solar activity, large volcanic eruptions and/or modulations of ocean circulation are potential triggers for this synchronicity.

Environmental and coastline changes controlling Holocene carbon accumulation rates in fjords of the western Strait of Magellan region

“…At these latitudes, recent studies from eastern Patagonia, which presents an inverse correlation between precipitation and zonal wind intensities (Garreaud et al, 2013), indicate a humid phase in the early Holocene between ca. 11.2 to 10.1 kyr BP while increased SWW intensity occurred from ca.10.1-8.3 kyr BP (Zolitschka et al, 2019). Composite analysis of pollen data from sites east of the Andes support the hypothesis that storm tracks weakened throughout Patagonia (41 � -55 � S) between ca.13-10 kyr BP, followed by stronger storm tracks in southern Patagonia than in northern Patagonia between ca.10-7 kyr BP (Nanavati et al, 2019).…”

Holocene variability in climate and oceanic conditions in the winter rainfall zone of South Africa—inferred from a high resolution diatom record from Verlorenvlei

“…5A). Greater frequencies of Nothofagus pollen, an indicator of enhanced precipitation, are recorded at Laguna Azul, southern Patagonia, from 3000 cal a bp (Zolitschka et al ., 2018). Changes in pollen influx at Fan Lake, South Georgia suggested a shift toward a cooler, albeit variable climate from 2700 cal a bp (Strother et al , 2015).…”

Testing lake-level reconstructions based on rock magnetic proxies for the sediment record of Laguna Cháltel (Patagonia, Argentina)

“…In this sense, the only regional strengthening of the SHW recorded by magnetic parameters for the central part of the lake is around 3650 cal yr BP. Zolitschka et al (2019) have proposed an expansion of the SHW belt, with stronger winds at the margins of the SHW belt and weaker winds in the central part. Taking this into account, Laguna Cháltel would be part of the northern margin of the SHW belt.…”