Onset and Evolution of Southern Annular Mode-Like Changes at Centennial Timescale

Moreno, Patricio I.; Vilanova, Isabel; Villa-Martínez, Rodrigo; Dunbar, Robert B.; Mucciarone, David A.; Kaplan, Michael R.; Garreaud, René D.; Rojas, Maisa; Moy, Christopher; Pol‐Holz, Ricardo De; Lambert, Fabrice

doi:10.1038/s41598-018-21836-6

Cited by 118 publications

(168 citation statements)

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“…This study is based on sediment cores from Lago Cipreses (cores PS0710SC1 + PS0710AT1-3, 365 cm depth) reported in Moreno et al (2018), Lago Guanaco (cores PS0404SC + PS0711GT1-7, 519 cm depth) reported in Moreno et al (2010), and Vega Ñandú (cores PS0405RC1A + PS0303AT1-4, 400 cm depth) reported in Villa-Martínez and . These consist of organic silts in the case of Lago Cipreses and Lago Guanaco, and various transitions from organic mud and peat in the case of Vega Ñandú.…”

Section: Resultsmentioning

confidence: 99%

“…In the case of Vega Ñandú we obtained the upper meter with a D-section Russian corer and the remaining section with a Wright square-rod piston corer. All sedimentary material was sent to the Quaternary paleoecology laboratory at Universidad de Chile and stored in a cold room at 4 • C. We documented the core stratigraphies with the aid of X-radiographs and textural descriptions of the sediments (Villa-Martínez and Moreno et al, 2010Moreno et al, , 2018.…”

Section: Methodsmentioning

confidence: 99%

“…The records from Lago Cipreses span uninterrupted since ∼14.3 ka (ka = 1,000 cal. yr BP) (Moreno et al, 2018). Lago Guanaco (51 • 52 ′ S, 72 • 52 ′ W, 200 m.a.sl.)…”

Section: Study Sitesmentioning

confidence: 99%

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Modulation of Fire Regimes by Vegetation and Site Type in Southwestern Patagonia Since 13 ka

et al. 2018

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The degree to which vegetation and site type have influenced fire regimes through the Holocene has not been investigated in detail in the temperate ecosystems of southern Patagonia. Here we present a first attempt using a paired-basin approach to study the evolution of fire regimes in sectors dominated by humid Nothofagus forests and the xeric Patagonian steppe in the Magallanes region of Chilean Patagonia (51 • S). We analyzed sediment cores from two small lakes and a bog located within the same climate zone on opposite sides of the forest-steppe ecotone, ∼28 km apart. The position of this biological boundary east of the Andes is controlled by the strength and position of the southern westerly winds, which constitute the sole source of precipitation throughout western Patagonia. Our results indicate that fires have occurred in the study region repeated times over the last ∼13,000 years at bi-and tridecadal timescales. Sectors currently dominated by Patagonian steppe feature high frequency and low magnitude of local fires, and vice versa in humid forests. Climate-driven expansion of Nothofagus scrubland/woodland into steppe environments over the last ∼4,200 years increased the magnitude and lowered the frequency of fire events, culminating with peak Nothofagus abundance, fire magnitude and frequency during the last millennium. We also detect divergences between lake-based vs. bog-based paleofire histories among paired sites located within the Patagonian steppe, ∼12 km apart, which we attribute to local burning of the bog at times of lowered water table. This divergence suggests to us that bog-based vegetation and fire histories exacerbate a local, azonal, signal blurring extra-local or regional regimes, thus accounting for some discrepancies in the Quaternary paleovegetation/paleoclimate literature of southern Patagonia.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Modulation of Fire Regimes by Vegetation and Site Type in Southwestern Patagonia Since 13 ka

et al. 2018

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“…Other SAM indices (or SH pressure / wind estimates) have been reconstructed over much longer time periods, many spanning back to AD 1000, using midlatitude proxy data such as tree rings and lake sediments (J. M. Jones & Widmann, 2003; Moreno et al, 2018; Villalba et al, 2012), ice core proxy data from Antarctica (I. D. Goodwin et al, 2014; I. D. Goodwin et al, 2004; Yang & Xiao, 2018), or multiproxy reconstructions based on a combination of midlatitude and Antarctic data (Abram et al, 2014; Zhang et al, 2010). Notably, as seen in South American (G. Silvestri & Vera, 2009) and Antarctic (G. J. Marshall et al, 2011, 2013) temperatures, recent work also suggests that many paleo–proxy relationships with the SAM are likely to be nonstationary, although this relationship varies regionally (Dätwyler et al, 2018).…”

Section: Past Characteristics Of the Sammentioning

confidence: 99%

The Southern Annular Mode: Variability, trends, and climate impacts across the Southern Hemisphere

Fogt

Marshall

2020

WIREs Climate Change

240

169

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The Southern Annular Mode (SAM) is the leading mode of extratropical Southern Hemisphere climate variability, associated with changes in the strength and position of the polar jet around Antarctica. This variability in the polar jet drives large fluctuations in the Southern Hemisphere climate, from the lower stratosphere into the troposphere, and stretching from the midlatitudes across the Southern Ocean to Antarctica. Notably, the SAM index has displayed marked positive trends in the austral summer season (stronger and poleward shifted westerlies), associated with stratospheric ozone loss. Historical reconstructions demonstrate that these recent positive SAM index values are unprecedented in the last millennia, and fall outside the range of natural climate variability. Despite these advances in the understanding of the SAM behavior, several areas of active research are identified that highlight gaps in our present knowledge. This article is categorized under: Paleoclimates and Current Trends > Earth System Behavior

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“…During this phase of moderate/higher temperatures, the reconstructed Southern Annular Mode (SAM) [119] has also exhibited less negative values. The core zone of the Southern Hemispheric Westerlies is located between 50 and 55 • S. In a positive phase of the SAM, this windbelt contracts towards the pole and weakens the winds between 40 and 50 • S, and vice versa [1,123]. After 1350 A.D., a significant decrease in the reconstructed temperature and also a prolonged period of exceptionally negative SAM indices can be considered to mark the (climatological) onset of the LIA.…”

Section: Late Holocene Glacial Oscillations In Southernmost Americamentioning

confidence: 99%

Late Holocene Glacial Fluctuations of Schiaparelli Glacier at Monte Sarmiento Massif, Tierra del Fuego (54°24′ S)

et al. 2019

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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 ±59 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.

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Onset and Evolution of Southern Annular Mode-Like Changes at Centennial Timescale

Cited by 118 publications

References 50 publications

Modulation of Fire Regimes by Vegetation and Site Type in Southwestern Patagonia Since 13 ka

Modulation of Fire Regimes by Vegetation and Site Type in Southwestern Patagonia Since 13 ka

The Southern Annular Mode: Variability, trends, and climate impacts across the Southern Hemisphere

Late Holocene Glacial Fluctuations of Schiaparelli Glacier at Monte Sarmiento Massif, Tierra del Fuego (54°24′ S)

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