The Experts below are selected from a list of 78267 Experts worldwide ranked by ideXlab platform
David Fink - One of the best experts on this subject based on the ideXlab platform.
-
The timing and nature of the Last Glacial cycle in New Zealand
Quaternary Science Reviews, 2019Co-Authors: James Shulmeister, David Fink, Glenn D. Thackray, Tammy M. Rittenour, Nicholas R. PattonAbstract:Abstract This paper constitutes a review of the Last (Otiran) glaciation in New Zealand, spanning marine isotope stages (MIS) 4-2. We highlight the nature of glaciation, which is characterised by exceptional sedimentation, relatively mild maritime climatic conditions and the widespread presence of water associated with proGlacial settings. These conditions produce Glacial systems characterised by extensive outwash fans and relatively small terminal moraines. Extensive recent geochronological work allows us to recognise at least eight Glacial advances during the Otiran. These occurred at 65 ± 3.25ka, 47.5 ± 3 ka, 38.5 ± 2 ka, 31.5 ± 3 ka, 26.5 ± 2 ka, 20.5 ± 2 ka, 17 ± 2 ka and 13 ± 1 ka, which we term the Otira 1 to 8 advances, respectively. Though the analytical uncertainty ranges for some of these advances overlap, all are independently distinguished through moraine morphologic relationships and/or stratigraphic relationships in outcrop. Major advances appear to be associated with climate influences such as periods of Southern Hemisphere insolation minima (65ka, and 31.5 ka advances), the Last Glacial maximum cooling (LGM) (20.5 ka) and periods of Antarctic cooling (13ka). The timing of greatest Glacial extent in the Last Glacial cycle is not simultaneous across New Zealand. The MIS 4 advance was the greatest in the southern South Island, while the MIS 3/2 advances (26.5 ka) were greatest in the central South Island. In the northern South Island and the North Island, MIS 4, MIS 3/2, and the Last Glacial maximum appear to be equivalent in extent. We attribute these spatio-temporal variations in the timing of maximum glaciation to precipitation changes related to a northward shift in the track of the westerlies.
-
Extensive glaciation in Transbaikalia, Siberia, at the Last Glacial Maximum
Quaternary Science Reviews, 2016Co-Authors: Martin Margold, David Fink, F. Preusser, John D. Jansen, Artem L. Gurinov, Alexandru T. Codilean, Natalya V. Reznichenko, Charles MifsudAbstract:Abstract Successively smaller Glacial extents have been proposed for continental Eurasia during the stadials of the Last Glacial period leading up to the Last Glacial Maximum (LGM). At the same time the large mountainous region east of Lake Baikal, Transbaikalia, has remained unexplored in terms of Glacial chronology despite clear geomorphological evidence of substantial past glaciations. We have applied cosmogenic 10Be exposure dating and optically stimulated luminescence to establish the first quantitative Glacial chronology for this region. Based on eighteen exposure ages from five moraine complexes, we propose that large mountain ice fields existed in the Kodar and Udokan mountains during Oxygen Isotope Stage 2, commensurate with the global LGM. These ice fields fed valley glaciers (>100 km in length) reaching down to the Chara Depression between the Kodar and Udokan mountains and to the valley of the Vitim River northwest of the Kodar Mountains. Two of the investigated moraines date to the Late Glacial, but indications of incomplete exposure among some of the sampled boulders obscure the specific details of the post-LGM Glacial history. In addition to the LGM ice fields in the highest mountains of Transbaikalia, we report geomorphological evidence of a much more extensive, ice-cap type glaciation at a time that is yet to be firmly resolved.
-
the early rise and late demise of new zealand s Last Glacial maximum
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Henrik Rother, David Fink, James Shulmeister, Charles Mifsud, Michael J Evans, Jeremy PughAbstract:Recent debate on records of southern midlatitude glaciation has focused on reconstructing glacier dynamics during the Last Glacial termination, with different results supporting both in-phase and out-of-phase correlations with Northern Hemisphere Glacial signals. A continuing major weakness in this debate is the lack of robust data, particularly from the early and maximum phase of southern midlatitude glaciation (∼30–20 ka), to verify the competing models. Here we present a suite of 58 cosmogenic exposure ages from 17 Last-Glacial ice limits in the Rangitata Valley of New Zealand, capturing an extensive record of Glacial oscillations between 28–16 ka. The sequence shows that the local Last Glacial maximum in this region occurred shortly before 28 ka, followed by several successively less extensive ice readvances between 26–19 ka. The onset of Termination 1 and the ensuing Glacial retreat is preserved in exceptional detail through numerous recessional moraines, indicating that ice retreat between 19–16 ka was very gradual. Extensive valley glaciers survived in the Rangitata catchment until at least 15.8 ka. These findings preclude the previously inferred rapid climate-driven ice retreat in the Southern Alps after the onset of Termination 1. Our record documents an early Last Glacial maximum, an overall trend of diminishing ice volume in New Zealand between 28–20 ka, and gradual deglaciation until at least 15 ka.
-
The early rise and late demise of New Zealand’s Last Glacial maximum
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Henrik Rother, David Fink, James Shulmeister, Charles Mifsud, Michael D. Evans, Jeremy PughAbstract:Recent debate on records of southern midlatitude glaciation has focused on reconstructing glacier dynamics during the Last Glacial termination, with different results supporting both in-phase and out-of-phase correlations with Northern Hemisphere Glacial signals. A continuing major weakness in this debate is the lack of robust data, particularly from the early and maximum phase of southern midlatitude glaciation (∼30–20 ka), to verify the competing models. Here we present a suite of 58 cosmogenic exposure ages from 17 Last-Glacial ice limits in the Rangitata Valley of New Zealand, capturing an extensive record of Glacial oscillations between 28–16 ka. The sequence shows that the local Last Glacial maximum in this region occurred shortly before 28 ka, followed by several successively less extensive ice readvances between 26–19 ka. The onset of Termination 1 and the ensuing Glacial retreat is preserved in exceptional detail through numerous recessional moraines, indicating that ice retreat between 19–16 ka was very gradual. Extensive valley glaciers survived in the Rangitata catchment until at least 15.8 ka. These findings preclude the previously inferred rapid climate-driven ice retreat in the Southern Alps after the onset of Termination 1. Our record documents an early Last Glacial maximum, an overall trend of diminishing ice volume in New Zealand between 28–20 ka, and gradual deglaciation until at least 15 ka.
Jean-claude Mareschal - One of the best experts on this subject based on the ideXlab platform.
-
Laurentide Ice Sheet basal temperatures during the Last Glacial cycle as inferred from borehole data
Climate of the Past, 2016Co-Authors: Carolyne Pickler, Hugo Beltrami, Jean-claude MareschalAbstract:Abstract. Thirteen temperature–depth profiles ( ≥ 1500 m) measured in boreholes in eastern and central Canada were inverted to determine the ground surface temperature histories during and after the Last Glacial cycle. The sites are located in the southern part of the region that was covered by the Laurentide Ice Sheet. The inversions yield ground surface temperatures ranging from −1.4 to 3.0 °C throughout the Last Glacial cycle. These temperatures, near the pressure melting point of ice, allowed basal flow and fast flowing ice streams at the base of the Laurentide Ice Sheet. Despite such conditions, which have been inferred from geomorphological data, the ice sheet persisted throughout the Last Glacial cycle. Our results suggest some regional trends in basal temperatures with possible control by internal heat flow.
-
Laurentide Ice Sheet basal temperatures at the Last Glacial Cycle as inferred from borehole data
Climate of the Past Discussions, 2015Co-Authors: Carolyne Pickler, Hugo Beltrami, Jean-claude MareschalAbstract:Abstract. Thirteen temperature-depth profiles (≥ 1500 m) measured in boreholes in eastern and central Canada were inverted to determine the ground surface temperature histories during and after the Last Glacial cycle. The sites are located in the southern part of the region covered by the Laurentide Ice Sheet. The inversions yield ground surface temperatures ranging from −1.4 to 3.0 °C throughout the Last Glacial cycle. These temperatures, near the pressure melting point of ice, allowed basal flow and fast flowing ice streams at the base of the Laurentide Ice Sheet. Despite such conditions, which have been inferred from geomorphological data, the ice sheet persisted throughout the Last Glacial cycle. Our results suggest some regional trends in basal temperatures with possible control by internal heat flow.
Jeremy Pugh - One of the best experts on this subject based on the ideXlab platform.
-
the early rise and late demise of new zealand s Last Glacial maximum
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Henrik Rother, David Fink, James Shulmeister, Charles Mifsud, Michael J Evans, Jeremy PughAbstract:Recent debate on records of southern midlatitude glaciation has focused on reconstructing glacier dynamics during the Last Glacial termination, with different results supporting both in-phase and out-of-phase correlations with Northern Hemisphere Glacial signals. A continuing major weakness in this debate is the lack of robust data, particularly from the early and maximum phase of southern midlatitude glaciation (∼30–20 ka), to verify the competing models. Here we present a suite of 58 cosmogenic exposure ages from 17 Last-Glacial ice limits in the Rangitata Valley of New Zealand, capturing an extensive record of Glacial oscillations between 28–16 ka. The sequence shows that the local Last Glacial maximum in this region occurred shortly before 28 ka, followed by several successively less extensive ice readvances between 26–19 ka. The onset of Termination 1 and the ensuing Glacial retreat is preserved in exceptional detail through numerous recessional moraines, indicating that ice retreat between 19–16 ka was very gradual. Extensive valley glaciers survived in the Rangitata catchment until at least 15.8 ka. These findings preclude the previously inferred rapid climate-driven ice retreat in the Southern Alps after the onset of Termination 1. Our record documents an early Last Glacial maximum, an overall trend of diminishing ice volume in New Zealand between 28–20 ka, and gradual deglaciation until at least 15 ka.
-
The early rise and late demise of New Zealand’s Last Glacial maximum
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Henrik Rother, David Fink, James Shulmeister, Charles Mifsud, Michael D. Evans, Jeremy PughAbstract:Recent debate on records of southern midlatitude glaciation has focused on reconstructing glacier dynamics during the Last Glacial termination, with different results supporting both in-phase and out-of-phase correlations with Northern Hemisphere Glacial signals. A continuing major weakness in this debate is the lack of robust data, particularly from the early and maximum phase of southern midlatitude glaciation (∼30–20 ka), to verify the competing models. Here we present a suite of 58 cosmogenic exposure ages from 17 Last-Glacial ice limits in the Rangitata Valley of New Zealand, capturing an extensive record of Glacial oscillations between 28–16 ka. The sequence shows that the local Last Glacial maximum in this region occurred shortly before 28 ka, followed by several successively less extensive ice readvances between 26–19 ka. The onset of Termination 1 and the ensuing Glacial retreat is preserved in exceptional detail through numerous recessional moraines, indicating that ice retreat between 19–16 ka was very gradual. Extensive valley glaciers survived in the Rangitata catchment until at least 15.8 ka. These findings preclude the previously inferred rapid climate-driven ice retreat in the Southern Alps after the onset of Termination 1. Our record documents an early Last Glacial maximum, an overall trend of diminishing ice volume in New Zealand between 28–20 ka, and gradual deglaciation until at least 15 ka.
Edouard Bard - One of the best experts on this subject based on the ideXlab platform.
-
Constraints on the magnitude and patterns of ocean cooling at the Last Glacial Maximum
Nature Geoscience, 2009Co-Authors: C. Waelbroeck, A. Paul, Michal Kucera, Antoni Rosell-melé, Mara Weinelt, Ralph Schneider, Alan C. Mix, Andrea Abelmann, Leanne Armand, Edouard BardAbstract:Observation-based reconstructions of sea surface temperature from relatively stable periods in the past, such as the Last Glacial Maximum, represent an important means of constraining climate sensitivity and evaluating model simulations(1). The first quantitative global reconstruction of sea surface temperatures during the Last Glacial Maximum was developed by the Climate Long-Range Investigation, Mapping and Prediction (CLIMAP) project in the 1970s and 1980s (refs 2,3). Since that time, several shortcomings of that earlier effort have become apparent(4). Here we present an updated synthesis of sea surface temperatures during the Last Glacial Maximum, rigorously defined as the period between 23 and 19 thousand years before present, from the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project(5). We integrate microfossil and geochemical reconstructions of surface temperatures and include assessments of the reliability of individual records. Our reconstruction reveals the presence of large longitudinal gradients in sea surface temperature in all of the ocean basins, in contrast to the simulations of the Last Glacial Maximum climate available at present(6,7).
-
Ice sheets and sea level of the Last Glacial Maximum
Eos Transactions American Geophysical Union, 2001Co-Authors: Peter U. Clark, Alan C. Mix, Edouard BardAbstract:What was the extent and volume of glaciers and ice sheets during the Last Glacial Maximum (LGM) centered on 21,000 calendar years ago? How much lower was global sea level as a result of growth of LGM ice sheets? What was the isostatic response to the global redistribution of mass (ice and water) during the LGM? What influence did LGM ice sheets have on global climate?
Charles Mifsud - One of the best experts on this subject based on the ideXlab platform.
-
Extensive glaciation in Transbaikalia, Siberia, at the Last Glacial Maximum
Quaternary Science Reviews, 2016Co-Authors: Martin Margold, David Fink, F. Preusser, John D. Jansen, Artem L. Gurinov, Alexandru T. Codilean, Natalya V. Reznichenko, Charles MifsudAbstract:Abstract Successively smaller Glacial extents have been proposed for continental Eurasia during the stadials of the Last Glacial period leading up to the Last Glacial Maximum (LGM). At the same time the large mountainous region east of Lake Baikal, Transbaikalia, has remained unexplored in terms of Glacial chronology despite clear geomorphological evidence of substantial past glaciations. We have applied cosmogenic 10Be exposure dating and optically stimulated luminescence to establish the first quantitative Glacial chronology for this region. Based on eighteen exposure ages from five moraine complexes, we propose that large mountain ice fields existed in the Kodar and Udokan mountains during Oxygen Isotope Stage 2, commensurate with the global LGM. These ice fields fed valley glaciers (>100 km in length) reaching down to the Chara Depression between the Kodar and Udokan mountains and to the valley of the Vitim River northwest of the Kodar Mountains. Two of the investigated moraines date to the Late Glacial, but indications of incomplete exposure among some of the sampled boulders obscure the specific details of the post-LGM Glacial history. In addition to the LGM ice fields in the highest mountains of Transbaikalia, we report geomorphological evidence of a much more extensive, ice-cap type glaciation at a time that is yet to be firmly resolved.
-
the early rise and late demise of new zealand s Last Glacial maximum
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Henrik Rother, David Fink, James Shulmeister, Charles Mifsud, Michael J Evans, Jeremy PughAbstract:Recent debate on records of southern midlatitude glaciation has focused on reconstructing glacier dynamics during the Last Glacial termination, with different results supporting both in-phase and out-of-phase correlations with Northern Hemisphere Glacial signals. A continuing major weakness in this debate is the lack of robust data, particularly from the early and maximum phase of southern midlatitude glaciation (∼30–20 ka), to verify the competing models. Here we present a suite of 58 cosmogenic exposure ages from 17 Last-Glacial ice limits in the Rangitata Valley of New Zealand, capturing an extensive record of Glacial oscillations between 28–16 ka. The sequence shows that the local Last Glacial maximum in this region occurred shortly before 28 ka, followed by several successively less extensive ice readvances between 26–19 ka. The onset of Termination 1 and the ensuing Glacial retreat is preserved in exceptional detail through numerous recessional moraines, indicating that ice retreat between 19–16 ka was very gradual. Extensive valley glaciers survived in the Rangitata catchment until at least 15.8 ka. These findings preclude the previously inferred rapid climate-driven ice retreat in the Southern Alps after the onset of Termination 1. Our record documents an early Last Glacial maximum, an overall trend of diminishing ice volume in New Zealand between 28–20 ka, and gradual deglaciation until at least 15 ka.
-
The early rise and late demise of New Zealand’s Last Glacial maximum
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Henrik Rother, David Fink, James Shulmeister, Charles Mifsud, Michael D. Evans, Jeremy PughAbstract:Recent debate on records of southern midlatitude glaciation has focused on reconstructing glacier dynamics during the Last Glacial termination, with different results supporting both in-phase and out-of-phase correlations with Northern Hemisphere Glacial signals. A continuing major weakness in this debate is the lack of robust data, particularly from the early and maximum phase of southern midlatitude glaciation (∼30–20 ka), to verify the competing models. Here we present a suite of 58 cosmogenic exposure ages from 17 Last-Glacial ice limits in the Rangitata Valley of New Zealand, capturing an extensive record of Glacial oscillations between 28–16 ka. The sequence shows that the local Last Glacial maximum in this region occurred shortly before 28 ka, followed by several successively less extensive ice readvances between 26–19 ka. The onset of Termination 1 and the ensuing Glacial retreat is preserved in exceptional detail through numerous recessional moraines, indicating that ice retreat between 19–16 ka was very gradual. Extensive valley glaciers survived in the Rangitata catchment until at least 15.8 ka. These findings preclude the previously inferred rapid climate-driven ice retreat in the Southern Alps after the onset of Termination 1. Our record documents an early Last Glacial maximum, an overall trend of diminishing ice volume in New Zealand between 28–20 ka, and gradual deglaciation until at least 15 ka.
