@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 {2646,
	title = {Abrupt mid-Holocene ice loss in the western Weddell Sea Embayment of Antarctica},
	journal = {Earth and Planetary Science Letters},
	volume = {518},
	year = {2019},
	month = {Jan-07-2019},
	pages = {127 - 135},
	abstract = {The glacial history of the westernmost Weddell Sea sector of Antarctica since the Last Glacial Maximum is virtually unknown, and yet it has been identified as critical for improving reliability of glacio-isostatic adjustment models that are required to correct satellite-derived estimates of ice sheet mass balance. Better knowledge of the glacial history of this region is also important for validating ice sheet models that are used to predict future contribution of the Antarctic ice sheet to sea level rise. Here we present a new Holocene deglacial chronology from a site on the Lassiter Coast of the Antarctic Peninsula, which is situated in the western Weddell Sea sector. Samples from 12 erratic cobbles and 18 bedrock surfaces from a series of presently-exposed ridges were analysed for cosmogenic Be-10 exposure dating, and a smaller suite of 7 bedrock samples for in situ C-14 dating. The resulting Be-10 ages are predominantly in the range 80-690 ka, whereas bedrock yielded much younger in situ C-14 ages, in the range 6.0-7.5 ka for samples collected from 138-385 m above the modern ice surface. From these we infer that the ice sheet experienced a period of abrupt thinning over a short time interval (no more than 2700 years) in the mid-Holocene, resulting in lowering of its surface by at least 250 m. Any late Holocene change in ice sheet thickness - such as re-advance, postulated by several modelling studies - must lie below the present ice sheet surface. The substantial difference in exposure ages derived from Be-10 and C-14 dating for the same samples additionally implies ubiquitous Be-10 inheritance acquired during ice-free periods prior to the last deglaciation, an interpretation that is consistent with our glacial-geomorphological field observations for former cold-based ice cover. The results of this study provide evidence for an episode of abrupt ice sheet surface lowering in the mid-Holocene, similar in rate, timing and magnitude to at least two other locations in Antarctica.},
	keywords = {Antarctica, cosmogenic dating in situ 14C, Holocene, Weddell Sea ice sheet},
	issn = {0012821X},
	doi = {10.1016/j.epsl.2019.05.002},
	url = {https://www.sciencedirect.com/science/article/pii/S0012821X19302638},
	author = {Johnson, Joanne S. and Nichols, Keir A. and Goehring, Brent M. and Balco, Greg and Schaefer, Joerg M.}
}
@article {2708,
	title = {Multiple independent records of local glacier variability on Nuussuaq, West Greenland, during the Holocene},
	journal = {Quaternary Science Reviews},
	volume = {215},
	year = {2019},
	month = {Jan-07-2019},
	pages = {253 - 271},
	abstract = {The sensitivity of mountain glaciers to small-scale climate fluctuations makes records of their past extent among the best proxies for identifying spatio-temporal climate variability. Here we build on the few existing Holocene records of local glacier change in Greenland by using three independent geochronological methods{\textemdash}proglacial lake sediment analysis, cosmogenic 10Be surface-exposure dating, and in situ 14C burial modeling{\textemdash}to reconstruct continuous records of Holocene glacier variability on Nuussuaq, West Greenland. 10Be ages of perched boulders indicate eastern Nuussuaq was deglaciated between \~{}11.0 and 10.5 ka. Radiocarbon-dated sediments from two lakes on Nuussuaq contain mineral-rich layers between \~{}9.6 and 9.0 and \~{}8.7{\textendash}8.0 cal ka BP that may be correlative with nearby ice sheet moraines deposited in the early Holocene. Multiple proxies for glacier size indicate frequent, high-amplitude glacier fluctuations superimposed on net glacier growth during the late Holocene, with significant ice expansion phases at \~{}3.7 ka, 2.8 ka, and throughout the past \~{}2 ka. Mean 10Be ages from five nested moraine crests confirm that local glacier extents on Nuussuaq culminated during both the Little Ice Age [\~{}1470 C.E. (n = 3) and 1750 C.E. (n = 3)] and the preceding centuries (\~{}520{\textendash}1320 C.E.; n = 11). Results reveal that local glaciers on Nuussuaq episodically advanced and retreated at centennial timescales throughout the Holocene, most likely in response to regional climate changes in West Greenland superimposed on the progressive insolation-driven cooling trend in the Northern Hemisphere. Our new 10Be moraine chronologies coupled with other glacier-size proxies corroborate an emerging pattern of significant summer cooling and glacier expansion in the centuries prior to the Little Ice Age in the Arctic.},
	keywords = {Cosmogenic 10Be, Cosmogenic in situ 14C, Greenland, Holocene, lake sediment, Mountain glaciers, Neoglaciation},
	issn = {02773791},
	doi = {10.1016/j.quascirev.2019.05.007},
	url = {https://www.sciencedirect.com/science/article/pii/S0277379118308771},
	author = {Schweinsberg, Avriel D. and Briner, Jason P. and Licciardi, Joseph M. and Bennike, Ole and Lifton, Nathaniel A. and Graham, Brandon L. and Young, Nicol{\'a}s E. and Schaefer, Joerg M. and Zimmerman, Susan H.}
}
@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.}
}
@article {2523,
	title = {Constraining Holocene 10Be production rates in Greenland},
	journal = {Journal of Quaternary Science},
	volume = {27},
	year = {2012},
	month = {Jan-01-2012},
	pages = {2 - 6},
	abstract = {The absence of a production rate calibration experiment on Greenland has limited the ability to link 10Be exposure dating chronologies of ice-margin change to independent records of rapid climate change. We use radiocarbon age control on Holocene glacial features near Jakobshavn Isbr{\ae}, western Greenland, to investigate 10Be production rates. The radiocarbon chronology is inconsistent with the 10Be age calculations based on the current globally averaged 10Be production rate calibration data set, but is consistent with the 10Be production rate calibration data set from north-eastern North America, which includes a calibration site nearby on north-eastern Baffin Island. Based on the best-dated feature available from the Jakobshavn Isbr{\ae} forefield, we derive a 10Be production rate value of 3.98 {\textpm} 0.24 atoms g a-1, using the {\textquoteleft}St{\textquoteright} scaling scheme, which overlaps with recently published reference 10Be production rates. We suggest that these 10Be production rate data, or the very similar data from north-eastern North America, are used on Greenland. Copyright {\textcopyright} 2011 John Wiley \& Sons, Ltd.},
	doi = {10.1002/jqs.1562},
	url = {http://doi.wiley.com/10.1002/jqs.1562},
	author = {Briner, Jason P. and Young, {\'a}s E. and Goehring, Brent M. and Schaefer, Joerg M.}
}
@article {444,
	title = {Regional beryllium-10 production rate calibration for late-glacial northeastern North America},
	journal = {Quaternary Geochronology},
	volume = {4},
	year = {2009},
	note = {id: 2034; PT: J; UT: WOS:000265163500003},
	pages = {93-107},
	abstract = {The major uncertainty in relating cosmogenic-nuclide exposure ages to ages measured by other dating methods comes from extrapolating nuclide production rates measured at globally scattered calibration sites to the sites of unknown age that are to be dated. This uncertainty can be reduced by locating production rate calibration sites that are similar in location and age to the sites to be dated. We use this strategy to reconcile exposure age and radiocarbon deglaciation chronologies for northeastern North America by compiling (10)Be production rate calibration measurements from independently dated late-glacial and early Holocene ice-marginal landforms in this region. 10Be production rates measured at these sites are 6-12\% lower than predicted by the commonly accepted global 10Be calibration data set used with any published production rate scaling scheme. In addition, the regional calibration data set shows significantly less internal scatter than the global calibration data set. Thus, this calibration data set can be used to improve both the precision and accuracy of exposure dating of regional late-glacial events. For example, if the global calibration data set is used to calculate exposure ages, the exposure-age deglaciation chronology for central New England is inconsistent with the deglaciation chronology inferred from radiocarbon dating and varve stratigraphy. We show that using the regional data set instead makes the exposure age and radiocarbon chronologies consistent. This increases confidence in correlating exposure ages of ice-marginal landforms in northeastern North America with glacial and climate events dated by other means. (c) 2008 Elsevier Ltd. All rights reserved.},
	issn = {1871-1014},
	doi = {10.1016/j.quageo.2008.09.001},
	author = {Balco, Greg and Briner, Jason and Finkel, Robert C. and Rayburn, John A. and Ridge, John C. and Schaefer, Joerg M.}
}
