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- Cuzzone, Joshua K., et al.
(author)
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Final deglaciation of the Scandinavian Ice Sheet and implications for the Holocene global sea-level budget
- 2016
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In: Earth and Planetary Science Letters. - : Elsevier BV. - 0012-821X .- 1385-013X. ; 448, s. 34-41
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Journal article (peer-reviewed)abstract
- The last deglaciation of the Scandinavian Ice Sheet (SIS) from similar to 21,000 to 13,000 yr ago is well constrained by several hundred Be-10 and C-14 ages. The subsequent retreat history, however, is established primarily from minimum-limiting C-14 ages and incomplete Baltic-Sea varve records, leaving a substantial fraction of final SIS retreat history poorly constrained. Here we develop a high-resolution chronology for the final deglaciation of the SIS based on 79 Be-10 cosmogenic exposure dates sampled along three transects spanning southern to northern Sweden and Finland. Combining this new chronology with existing Be-10 ages on deglaciation since the Last Glacial Maximum shows that rates of SIS margin retreat were strongly influenced by deglacial millennial-scale climate variability and its effect on surface mass balance, with regional modulation of retreat associated with dynamical controls. Ice-volume estimates constrained by our new chronology suggest that the SIS contributed 8 m sea-level equivalent to global sea-level rise between similar to 14.5 ka and 10 ka. Final deglaciation was largely complete by similar to 10.5 ka, with highest rates of sea-level rise occurring during the Bolling-Allerod, a 50% decrease during the Younger Dryas, and a rapid increase during the early Holocene. Combining our SIS volume estimates with estimated contributions from other remaining Northern Hemisphere ice sheets suggests that the Antarctic Ice Sheet (AIS) contributed 14.4 +/- 5.9 m to global sea-level rise since 13 ka. This new constraint supports those studies that indicate that an ice volume of 15 m or more of equivalent sea-level rise was lost from the AIS during the last deglaciation.
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| 2. |
- Reilly, Brendan T., et al.
(author)
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Holocene break-up and reestablishment of the Petermann Ice Tongue, Northwest Greenland
- 2019
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In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 218, s. 322-342
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Journal article (peer-reviewed)abstract
- Over the last decade, two major calving events of the Petermann Ice Tongue in Northwest Greenland have led to speculation on its future stability and contribution to further Greenland Ice Sheet mass loss. However, it has been unclear if these events are anomalous or typical within the context of limited historical observations. We extend the historical record of the floating ice tongue using the stratigraphy of Petermann Fjord sediments to provide a longer-term perspective. Computed tomography (CT) scans, X-Ray Fluorescence (XRF) scans, Ice-Rafted Debris (IRD) counts, and the magnetic properties of specific particle size fractions constrain changes in depositional processes and sediment sources at our core sites, allowing for reconstructions of past behavior of the Petermann Ice Tongue. Radiocarbon dating of foraminifera, Pb-210, and paleomagnetic secular variation (PSV) provide age control and help to address uncertainties in radiocarbon reservoir ages. A floating ice tongue in Petermann Fjord formed in late glacial time as Petermann Glacier retreated from an advanced grounded position. This paleo-ice tongue broke-up during the early Holocene when high northern latitude summer insolation was higher than present. After gradual regrowth of the ice tongue associated with regional cooling, the ice tongue reached its historical extent only within the last millennium. Little or no ice tongue was present for nearly 5000 years during the middle Holocene, when decadal mean regional temperatures are estimated to be 0.8-2.9 degrees C higher than preindustrial (1750 CE) and seasonal sea-ice in the Lincoln Sea was reduced. This pre-historical behavior shows that recent anthropogenic warming may already be in the range of ice tongue instability and future projected warming increases the risk of ice tongue break-up by the mid-21st Century.
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