@article {denton_zealandia_2021,
	title = {The Zealandia Switch: Ice age climate shifts viewed from Southern Hemisphere moraines},
	journal = {Quaternary Science Reviews},
	volume = {257},
	year = {2021},
	month = {04/2021},
	pages = {106771},
	abstract = {Two fundamental questions about the ice-age climate system await satisfactory resolution. First, if summer solar radiation intensity truly controls the orbital signature of the last glacial cycle, then why were major climatic shifts, including the last termination, globally synchronous? Second, what caused the millennial-scale climate oscillations superimposed on this cycle? We address these questions from a Southern Hemisphere perspective focused on mid-latitude mountain ice fields. We put particular emphasis on the last glacial termination, which involved both orbital-scale and millennial-scale climate elements and has generally well-resolved chronological control. Sustained retreat of mountain glaciers, documented by detailed mapping and chronology of glacial landforms in the Southern Alps and southern Andes, marked the termination of the last ice age, beginning \~{}18 kyrs ago and involved a change from glacial to near-interglacial atmospheric temperature within a millennium or two. A rapid poleward shift of the Subtropical Front, delineating the northern margin of the Southern Ocean, \~{}18 kyrs ago implies a concurrent poleward shift of the austral westerlies and leads us to hypothesize a southern origin for the dominant phase of the last glacial termination. Together with interhemispheric paleoclimate records and with results of coupled ocean-atmosphere climate modeling, these findings suggest a big, fast, and global end to the last ice age in which a southern-sourced warming episode linked the hemispheres. We posit that a shift in the Southern Ocean circulation and austral westerly wind system, tied to southern orbital forcing, caused this global warming episode by affecting the tropical heat engine and hence global climate. Central to this hypothesis, dubbed the {\textquoteleft}Zealandia Switch{\textquoteright}, is the location of the Australia and Zealandia continents relative to Southern Hemisphere oceanic and atmospheric circulation. Coupled ocean-atmosphere climate modeling shows that the locus of the austral westerlies, whether in a more equatorward position representing a glacial-mode climate or in a poleward-shifted position marking interglacial-mode climate, has profound effects on oceanic and associated atmospheric linkages between the tropical Pacific and the Southern Ocean. Shifts in the austral westerlies have global climatic consequences, especially through resulting changes in the greenhouse gas content of the atmosphere and altered heat flux from the tropical Pacific into the Northern and Southern Hemispheres. We suggest that the last glacial termination was a global warming episode that led to extreme seasonality in northern latitudes by stimulating a flush of meltwater and icebergs into the North Atlantic from adjoining ice sheets. This fresh-water influx resulted in widespread North Atlantic sea ice that caused very cold boreal winters, thus amplifying the annual southward shift of the Intertropical Convergence Zone and the monsoonal rain belts. We further suggest that muted manifestations of the Zealandia Switch mechanism were responsible for smaller, recurring millennial-scale climate oscillations within the last glacial cycle.},
	keywords = {Climate dynamics, Climate modeling, Cosmogenic isotopes, Geomorphology, Glacial, Glaciation, paleoclimatology, Quaternary, South Pacific Ocean, Southern Hemisphere westerlies, Southern Ocean},
	issn = {0277-3791},
	doi = {10.1016/j.quascirev.2020.106771},
	url = {https://www.sciencedirect.com/science/article/pii/S0277379120307332},
	author = {Denton, George H. and Putnam, Aaron E. and Russell, Joellen L. and Barrell, David J. A. and Schaefer, Joerg M. and Kaplan, Michael R. and Strand, Peter D.}
}
@article {39,
	title = {Holocene glacier history of the Lago Argentino basin, Southern Patagonian Icefield},
	journal = {Quaternary Science Reviews},
	volume = {101},
	year = {2014},
	pages = {124-145},
	abstract = {We present new geomorphic, stratigraphic, and chronologic data for Holocene glacier fluctuations in the Lago Argentino basin on the eastern side of the southern Patagonian Andes. Chronologic control is based on 14C and surface-exposure 10Be dating. After the Lateglacial maximum at 13,000 cal yrs BP, the large ice lobes that filled the eastern reaches of Lago Argentino retreated and separated into individual outlet glaciers; this recession was interrupted only by a stillstand or minor readvance at 12,200 cal yrs BP. The eight largest of these individual outlet glaciers are, from north to south: Upsala, Agassiz, Onelli, Spegazzini, Mayo, Ameghino, Perito Moreno, and Grande (formerly Fr{\'\i}as). Holocene recession of Upsala Glacier exposed Brazo Cristina more than 10,115 {\textpm} 100 cal yrs BP, and reached inboard of the Holocene moraines in Agassiz Este Valley by 9205 {\textpm} 85 cal yrs BP; ice remained in an inboard position until 7730 {\textpm} 50 cal yrs BP. Several subsequent glacier readvances are well documented for the Upsala and Fr{\'\i}as glaciers. The Upsala Glacier readvanced at least seven times, the first being a relatively minor expansion {\textendash} documented only in stratigraphic sections {\textendash} between 7730 {\textpm} 50 and 7210 {\textpm} 45 cal yrs BP. The most extensive Holocene advances of Upsala Glacier resulted in the deposition of the Pearson 1 moraines and related landforms, which are divided into three systems. The Pearson 1a advance occurred about 6000{\textendash}5000 cal yrs BP and was followed by the slightly less-extensive Pearson 1b and 1c advances dated to 2500{\textendash}2000 and 1500{\textendash}1100 cal yrs BP, respectively. Subsequent advances of Upsala Glacier resulted in deposition of the Pearson 2 moraines and corresponding landforms, also separated into three systems, Pearson 2a, 2b, and 2c, constructed respectively at \~{}700, >400, and <300 cal yrs BP to the early 20th century. Similar advances are also recorded by moraine systems in front of Grande Glacier and herein separated into the Fr{\'\i}as 1 and Fr{\'\i}as 2a, 2b, and 2c. The Onelli and Ameghino glacier valleys also preserve older Holocene moraines. In the Agassiz, Spegazzini, and Mayo valleys, ice of the late-Holocene advances appears to have overridden landforms equivalent in age to Pearson 1. Perito Moreno Glacier is an extreme case in which ice of historical (Pearson 2c) advances overrode all older Holocene moraines. Based on the distribution and number of moraines preserved, we infer that the response to climate differed among the Lago Argentino outlet glaciers during the Holocene. This led us to examine the effects of climatic and non-climatic factors on individual glaciers. As a consequence, we detected an important effect of the valley geometry (hypsometry) on the timing and magnitude of glacier response to climate change. These results indicate that caution is needed in correlating moraines among glacier forefields without firm morpho-stratigraphic and age control. Finally, we note important similarities and differences between the overall moraine chronology in the Lago Argentino basin and that in other areas of southern South America and elsewhere in the Southern Hemisphere.},
	issn = {0277-3791},
	doi = {10.1016/j.quascirev.2014.06.026},
	url = {http://www.sciencedirect.com/science/article/pii/S0277379114002558},
	author = {Strelin, Jorge A. and Kaplan, Michael R. and Vandergoes, Marcus J. and Denton, George H. and Schaefer, Joerg M.}
}
