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The timing and effect of the earliest human arrivals in North America 期刊论文
NATURE, 2020
作者:  Lorena Becerra-Valdivia;  Thomas Higham
收藏  |  浏览/下载:27/0  |  提交时间:2020/08/09

The peopling of the Americas marks a major expansion of humans across the planet. However, questions regarding the timing and mechanisms of this dispersal remain, and the previously accepted model (termed '  Clovis-first'  )-suggesting that the first inhabitants of the Americas were linked with the Clovis tradition, a complex marked by distinctive fluted lithic points(1)-has been effectively refuted. Here we analyse chronometric data from 42 North American and Beringian archaeological sites using a Bayesian age modelling approach, and use the resulting chronological framework to elucidate spatiotemporal patterns of human dispersal. We then integrate these patterns with the available genetic and climatic evidence. The data obtained show that humans were probably present before, during and immediately after the Last Glacial Maximum (about 26.5-19 thousand years ago)(2,3)but that more widespread occupation began during a period of abrupt warming, Greenland Interstadial 1 (about 14.7-12.9 thousand years beforead 2000)(4). We also identify the near-synchronous commencement of Beringian, Clovis and Western Stemmed cultural traditions, and an overlap of each with the last dates for the appearance of 18 now-extinct faunal genera. Our analysis suggests that the widespread expansion of humans through North America was a key factor in the extinction of large terrestrial mammals.


A Bayesian age model suggests that human dispersal to the Americas probably began before the Last Glacial Maximum, overlapping with the last dates of appearance for several faunal genera.


  
Ice retreat in Wilkes Basin of East Antarctica during a warm interglacial 期刊论文
NATURE, 2020, 583 (7817) : 554-+
作者:  T. Blackburn;  G. H. Edwards;  S. Tulaczyk;  M. Scudder;  G. Piccione;  B. Hallet;  N. McLean;  J. C. Zachos;  B. Cheney;  J. T. Babbe
收藏  |  浏览/下载:21/0  |  提交时间:2020/08/09

Uranium isotopes in subglacial precipitates from the Wilkes Basin of the East Antarctic Ice Sheet reveal ice retreat during a warm Pleistocene interglacial period about 400,000 years ago.


Efforts to improve sea level forecasting on a warming planet have focused on determining the temperature, sea level and extent of polar ice sheets during Earth'  s past interglacial warm periods(1-3). About 400,000 years ago, during the interglacial period known as Marine Isotopic Stage 11 (MIS11), the global temperature was 1 to 2 degrees Celsius greater(2)and sea level was 6 to 13 metres higher(1,3). Sea level estimates in excess of about 10 metres, however, have been discounted because these require a contribution from the East Antarctic Ice Sheet(3), which has been argued to have remained stable for millions of years before and includes MIS11(4,5). Here we show how the evolution of(234)U enrichment within the subglacial waters of East Antarctica recorded the ice sheet'  s response to MIS11 warming. Within the Wilkes Basin, subglacial chemical precipitates of opal and calcite record accumulation of(234)U (the product of rock-water contact within an isolated subglacial reservoir) up to 20 times higher than that found in marine waters. The timescales of(234)U enrichment place the inception of this reservoir at MIS11. Informed by the(234)U cycling observed in the Laurentide Ice Sheet, where(234)U accumulated during periods of ice stability(6)and was flushed to global oceans in response to deglaciation(7), we interpret our East Antarctic dataset to represent ice loss within the Wilkes Basin at MIS11. The(234)U accumulation within the Wilkes Basin is also observed in the McMurdo Dry Valleys brines(8-10), indicating(11)that the brine originated beneath the adjacent East Antarctic Ice Sheet. The marine origin of brine salts(10)and bacteria(12)implies that MIS11 ice loss was coupled with marine flooding. Collectively, these data indicate that during one of the warmest Pleistocene interglacials, the ice sheet margin at the Wilkes Basin retreated to near the precipitate location, about 700 kilometres inland from the current position of the ice margin, which-assuming current ice volumes-would have contributed about 3 to 4 metres(13)to global sea levels.


  
Distributed Acoustic Sensing of Seismic Properties in a Borehole Drilled on a Fast-Flowing Greenlandic Outlet Glacier 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2020, 47 (13)
作者:  Booth, Adam D.;  Christoffersen, Poul;  Schoonman, Charlotte;  Clarke, Andy;  Hubbard, Bryn;  Law, Robert;  Doyle, Samuel H.;  Chudley, Thomas R.;  Chalari, Athena
收藏  |  浏览/下载:10/0  |  提交时间:2020/06/09
Distributed Acoustic Sensing (DAS)  Vertical Seismic Profile (VSP)  Greenland Ice Sheet  anisotropy  subglacial sediment  borehole surveying  
The Spatiotemporal Variability of Cloud Radiative Effects on the Greenland Ice Sheet Surface Mass Balance 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2020, 47 (12)
作者:  Izeboud, M.;  Lhermitte, S.;  Van Tricht, K.;  Lenaerts, J. T. M.;  Van Lipzig, N. P. M.;  Wever, N.
收藏  |  浏览/下载:9/0  |  提交时间:2020/06/09
cloud radiative effect  Greenland ice sheet  cloud impact  
Warm Temperature Extremes Across Greenland Connected to Clouds 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2020, 47 (9)
作者:  Gallagher, Michael R.;  Chepfer, Helene;  Shupe, Matthew D.;  Guzman, Rodrigo
收藏  |  浏览/下载:6/0  |  提交时间:2020/07/02
Greenland ice sheet  cloud impacts  energy budget  warming events  Arctic climate  
Direct Observation of Winter Meltwater Drainage From the Greenland Ice Sheet 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2020, 47 (9)
作者:  Pitcher, Lincoln H.;  Smith, Laurence C.;  Gleason, Colin J.;  Miege, Clement;  Ryan, Johnny C.;  Hagedorn, Birgit;  van As, Dirk;  Chu, Winnie;  Forster, Richard R.
收藏  |  浏览/下载:15/0  |  提交时间:2020/07/02
Greenland Ice Sheet  subglacial hydrology  meltwater retention  meltwater storage  surface melt  winter  
Greenland Ice Sheet Contribution to 21st Century Sea Level Rise as Simulated by the Coupled CESM2.1-CISM2.1 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2020, 47 (9)
作者:  Muntjewerf, Laura;  Petrini, Michele;  Vizcaino, Miren;  da Silva, Carolina Ernani;  Sellevold, Raymond;  Scherrenberg, Meike D. W.;  Thayer-Calder, Katherine;  Bradley, Sarah L.;  Lenaerts, Jan T. M.;  Lipscomb, William H.;  Lofverstrom, Marcus
收藏  |  浏览/下载:16/0  |  提交时间:2020/07/02
Greenland Ice Sheet  Sea level rise  21st century  
Continuity of Ice Sheet Mass Loss in Greenland and Antarctica From the GRACE and GRACE Follow-On Missions 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2020, 47 (8)
作者:  Velicogna, Isabella;  Mohajerani, Yara;  Geruo, A.;  Landerer, Felix;  Mouginot, Jeremie;  Noel, Brice;  Rignot, Eric;  Sutterley, Tyler;  van den Broeke, Michiel;  Wessem, Melchior;  Wiese, David
收藏  |  浏览/下载:9/0  |  提交时间:2020/07/02
Antarctica  Greenland  GRACE  mass balance  climate change  glaciology  
Calving Seasonality Associated With Melt-Undercutting and Lake Ice Cover 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2020, 47 (8)
作者:  Mallalieu, Joseph;  Carrivick, Jonathan L.;  Quincey, Duncan J.;  Smith, Mark W.
收藏  |  浏览/下载:8/0  |  提交时间:2020/07/02
calving  glacial lake  Greenland  outburst flood  structure-from-motion  time-lapse  
Eurasian Ice Sheet collapse was a major source of Meltwater Pulse 1A 14,600 years ago 期刊论文
NATURE GEOSCIENCE, 2020, 13 (5)
作者:  Brendryen, Jo;  Haflidason, Haflidi;  Yokoyama, Yusuke;  Haaga, Kristian Agasoster;  Hannisdal, Bjarte
收藏  |  浏览/下载:9/0  |  提交时间:2020/05/13