scholarly journals The timing of fjord formation and early glaciations in North and Northeast Greenland

2020 ◽  
Author(s):  
Vivi Kathrine Pedersen ◽  
Nicolaj Krog Larsen ◽  
David Lundbek Egholm
Keyword(s):  
Late Miocene ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Early History ◽  
Early Pleistocene ◽  
Late Pliocene ◽  
Isostatic Uplift ◽  
History Of ◽  
Erosional Unloading ◽  
North Greenland

<p>The timing and extent of early glaciations in Greenland, and their co-evolution with the underlying landscape remain elusive. In this study, we explore the timing of fjord erosion in Northeast and North Greenland between Scoresby Sund (70°N) and Independence Fjord (82°N). By determining the timing of fjord formation, we can improve our understanding of the early history of the Greenland Ice Sheet in these regions.</p><p>We use the concept of geophysical relief to estimate fjord erosion and calculate the subsequent flexural isostatic response to erosional unloading. The timing of erosion and isostatic uplift is constrained by marine sediments of late Pliocene-early Pleistocene age that are now exposed on land between ~24 and 230 m a.s.l.</p><p>We find that the northern Independence Fjord system must have formed by glacial erosion at average rates of ~0.5-1 mm/yr since ~2.5 Ma, in order to explain the current elevation of the marine Kap København Formation by erosion-induced isostatic uplift. In contrast, fjord formation in the outer parts of southward Scoresby Sund commenced before the Pleistocene, most likely in late Miocene, and continued throughout the Pleistocene by fjord formation progressing inland. Our results suggest that the inception of the Greenland Ice Sheet began in the central parts of Northeast Greenland before the Pleistocene and spread to North Greenland only at the onset of the Pleistocene.  </p>

scholarly journals The timing of fjord formation and early glaciations in North and Northeast Greenland

2021 ◽  
Author(s):  
Vivi Kathrine Pedersen ◽  
Nicolaj Krog Larsen ◽  
David Lundbek Egholm
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Early History ◽  
Early Pleistocene ◽  
East Greenland ◽  
Late Pliocene ◽  
Isostatic Uplift ◽  
History Of ◽  
Erosional Unloading ◽  
North Greenland

<p>The timing and extent of early glaciations in Greenland, and their co-evolution with the underlying landscape remain elusive. In this study, we explore the timing of fjord formation in Northeast and North Greenland, between Scoresby Sund (70°N) and Independence Fjord (82°N). By determining the timing of fjord formation, we can improve our understanding of the early history of the Greenland Ice Sheet in these regions. We use the concept of geophysical relief to estimate fjord erosion volumes and calculate the subsequent flexural isostatic response to erosional unloading. The timing of erosion and isostatic uplift is constrained by marine sediments of late Pliocene-early Pleistocene age that are now exposed on land between ~24 and 230 m a.s.l. The late Pliocene-early Pleistocene sediments themselves attest to a time of limited ice cover in Greenland, with temperatures as much as 6-8 °C higher than present (e.g. Bennike et al., 2010).</p><p>We find that the northern Independence Fjord system must have formed by glacial erosion since the deposition of the marine late Pliocene-early Pleistocene sediments at ~2.5 Ma, in order to explain the current elevation of the sediments by erosion-induced isostatic uplift. In contrast, fjord formation in the outer parts of southward Scoresby Sund commenced prior to the Pleistocene, most likely in late Miocene, and continued throughout the Pleistocene with fjord formation progressing inland. Our results suggest that the inception of the Greenland Ice Sheet began in the central parts of Northeast Greenland before the Pleistocene and spread to North Greenland only at the onset of the Pleistocene. </p><p>References:</p><p>Bennike, O., Knudsen, K.L., Abrahamsen, N., Böcher, J., Cremer, H., and Wagner, B., 2010, Early Pleistocene sediments on Store Koldewey, north­east Greenland: Boreas v. 39, p. 603–619, https://doi.org /10.1111/j.1502-3885.2010.00147.x.</p>

scholarly journals Glacial history of Inglefield Land, north Greenland from combined in-situ <sup>10</sup>Be and <sup>14</sup>C exposure dating

2020 ◽  
Author(s):  
Anne Sofie Søndergaard ◽  
Nicolaj Krog Larsen ◽  
Olivia Steinemann ◽  
Jesper Olsen ◽  
Svend Funder ◽  
...  
Keyword(s):  
Climate Changes ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Age ◽  
Glacial History ◽  
Holocene Climate ◽  
Exposure Dating ◽  
History Of ◽  
North Greenland

Abstract. Exposing the sensitivity of the Greenland Ice Sheet (GrIS) to Holocene climate changes is a key prerequisite for understanding the future response of the ice sheet to global warming. In this study, we present new information on the Holocene glacial history of the GrIS in Inglefield Land, north Greenland. We use 10Be and in-situ 14C exposure dating to constrain the timing of deglaciation in the area and radiocarbon dating of reworked molluscs and wood fragments to constrain when the ice sheet retreated behind its present-day extent. The 10Be ages are scattered ranging from c. 92.7 to 6.8 ka whereas the in-situ 14C ages range from c. 14.2 to 6.7 ka. Almost half of the apparent 10Be ages predate the Last Glacial Maximum and up to 89 % are to some degree affected by nuclide inheritance. Based on the few reliable 10Be ages, the in-situ 14C ages and existing radiocarbon ages from Inglefield Land, we find that the deglaciation along the coast commenced c. 8.6–8.3 cal. ka BP in the western part and c. 7.9 ka in the central part, following the opening of Nares Strait and arrival of warm waters. The ice margin reached its present-day position c. 8.2 ka at the Humboldt Glacier and c. 6.7 ka in the central part of Inglefield Land. Radiocarbon ages of reworked molluscs and wood fragments show that the ice margin was behind its present-day extent from c. 5.8 to 0.5 cal. ka BP. After 0.5 cal. ka BP, the ice advanced towards its Little Ice Age position. Our results emphasize that the slowly eroding and possibly cold-based ice in north Greenland makes it difficult to constrain the deglaciation history based on 10Be ages alone unless it is paired with in-situ 14C ages. Further, combining our findings with those of recently published studies reveals distinct differences between deglaciation patterns of northwest and north Greenland. Deglaciation of the land areas in northwest Greenland occurred earlier than in north Greenland and periods of restricted ice extent were longer, spanning middle and late Holocene. Overall, this highlights past ice sheet sensitivity towards Holocene climate changes in an area where little information was available just a few years ago.

scholarly journals Snapshots of the Greenland ice sheet configuration in the Pliocene to early Pleistocene

2011 ◽  
Vol 57 (205) ◽  
pp. 871-880 ◽  
Author(s):  
Anne M. Solgaard ◽  
Niels Reeh ◽  
Peter Japsen ◽  
Tove Nielsen
Keyword(s):  
Flow Model ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Early Pleistocene ◽  
Pleistocene Glaciations ◽  
Ice Flow ◽  
Late Pliocene ◽  
Ice Caps ◽  
Climate Reconstructions

AbstractThe geometry of the ice sheets during the Pliocene to early Pleistocene is not well constrained. Here we apply an ice-flow model in the study of the Greenland ice sheet (GIS) during three extreme intervals of this period constrained by geological observations and climate reconstructions. We study the extent of the GIS during the Mid-Pliocene Warmth (3.3–3.0 Ma), its advance across the continental shelf during the late Pliocene to early Pleistocene glaciations (3.0–2.4 Ma) as implied by offshore geological studies, and the transition from glacial to interglacial conditions around 2.4 Ma as deduced from the deposits of the Kap København Formation, North Greenland. Our experiments show that no coherent ice sheet is likely to have existed in Greenland during the Mid-Pliocene Warmth and that only local ice caps may have been present in the coastal mountains of East Greenland. Our results illustrate the variability of the GIS during the Pliocene to early Pleistocene and underline the importance of including independent estimates of the GIS in studies of climate during this period. We conclude that the GIS did not exist throughout the Pliocene to early Pleistocene, and that it melted during interglacials even during the late Pliocene climate deterioration.

scholarly journals Glacial history of Inglefield Land, north Greenland from combined in situ <sup>10</sup>Be and <sup>14</sup>C exposure dating

2020 ◽  
Vol 16 (5) ◽  
pp. 1999-2015
Author(s):  
Anne Sofie Søndergaard ◽  
Nicolaj Krog Larsen ◽  
Olivia Steinemann ◽  
Jesper Olsen ◽  
Svend Funder ◽  
...  
Keyword(s):  
Climate Changes ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Age ◽  
Glacial History ◽  
Holocene Climate ◽  
Exposure Dating ◽  
History Of ◽  
North Greenland

Abstract. Determining the sensitivity of the Greenland Ice Sheet (GrIS) to Holocene climate changes is a key prerequisite for understanding the future response of the ice sheet to global warming. In this study, we present new information on the Holocene glacial history of the GrIS in Inglefield Land, north Greenland. We use 10Be and in situ 14C exposure dating to constrain the timing of deglaciation in the area and radiocarbon dating of reworked molluscs and wood fragments to constrain when the ice sheet retreated behind its present-day extent. The 10Be ages are scattered ranging from ca. 92.7 to 6.8 ka, whereas the in situ 14C ages range from ca. 14.2 to 6.7 ka. Almost half of the apparent 10Be ages predate the Last Glacial Maximum and up to 89 % are to some degree affected by nuclide inheritance. Based on the few reliable 10Be ages, the in situ 14C ages and existing radiocarbon ages from Inglefield Land, we find that the deglaciation along the coast commenced at ca. 8.6–8.3 ka cal BP in the western part and ca. 7.9 ka in the central part, following the opening of Nares Strait and arrival of warm waters. The ice margin reached its present-day position at ca. 8.2 ka at the Humboldt Glacier and ca. 6.7 ka in the central part of Inglefield Land. Radiocarbon ages of reworked molluscs and wood fragments show that the ice margin was behind its present-day extent from ca. 5.8 to 0.5 ka cal BP. After 0.5 ka cal BP, the ice advanced towards its Little Ice Age position. Our results emphasize that the slowly eroding and possibly cold-based ice in north Greenland makes it difficult to constrain the deglaciation history based on 10Be ages alone unless they are paired with in situ 14C ages. Further, combining our findings with those of recently published studies reveals distinct differences between deglaciation patterns of northwest and north Greenland. Deglaciation of the land areas in northwest Greenland occurred earlier than in north Greenland, and periods of restricted ice extent were longer, spanning the Middle and Late Holocene. Overall, this highlights past ice sheet sensitivity to Holocene climate changes in an area where little information was available just a few years ago.

Simulations of large climate transition occurring at high and low latitudes during the late Pliocene (3.3 Ma) and the Plio/Pleistocene (3-2.5 Ma) boundary

2020 ◽  
Author(s):  
Ning Tan ◽  
Emma Yule ◽  
Gilles Ramstein ◽  
Doris Barboni ◽  
Rani Raj ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Energy Transport ◽  
Hydrological Cycle ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Large Change ◽  
Early Pleistocene ◽  
Oceanic Circulation ◽  
Late Pliocene ◽  
Opening And Closing

&lt;p&gt;The late Pliocene corresponds to a large cooling over Northern Hemisphere associated with sporadic occurrences of glaciations. The most important event occurred during the marine isotope stage M2 (MIS M2, 3.312&amp;#8211;3.264 Ma) when a large glaciation took place with a sea level drop from 20 to 60 m, but its duration is short and the summer insolation forcing change at 65&amp;#176;N is weak. De Schepper et al (2013) invoked to explain the onset and termination of this glaciation with the opening and closing of the Central American Seaway (shallow CAS). Based on their hypothesis, we have intensively studied the onset mechanism of&amp;#160; MIS M2 through a series of sensitivity experiments using the IPSL AOGCM and the asynchronous coupling with an Ice sheet model (GRISLI). Our results demonstrate that the shallow CAS helps to precondition the low-latitude oceanic circulation and affects the related northward energy transport, but cannot alone explain the onset of the M2 glaciation, the most important contribution on MIS M2 are from the large change of pCO&lt;sub&gt;2&lt;/sub&gt; as well as the internal feedbacks of vegetation and ice sheet. Moreover, we have also investigated the period from the late Pliocene to the early Pleistocene (3-2.5 Ma) through a transient-like simulation using the same AOGCM and ISM. This enables to simulate the Greenland Ice Sheet (GRIS) onset and development using the pCO&lt;sub&gt;2&lt;/sub&gt; reconstructions from different proxies. All these simulations were analyzed with emphasis on cryosphere and focused on the Northern Hemisphere (mid-to-high latitudes). Here we used the same modeling simulations but with a focus over the tropical Africa. We first depict the large changes of temperatures and hydrological cycle produced over this area during these two periods and compare our data to reconstructions. Moreover, by prescribing our climate results as inputs for the vegetation model (Biome4), we compare more directly the simulated plant functional types (PFTs) with that constructed by the pollen data. In addition, we further quantify the respective impact of various driving factors on these PFTs variations.&lt;/p&gt;

scholarly journals A multimillion-year-old record of Greenland vegetation and glacial history preserved in sediment beneath 1.4 km of ice at Camp Century

2021 ◽  
Vol 118 (13) ◽  
pp. e2021442118
Author(s):  
Andrew J. Christ ◽  
Paul R. Bierman ◽  
Joerg M. Schaefer ◽  
Dorthe Dahl-Jensen ◽  
Jørgen P. Steffensen ◽  
...  
Keyword(s):  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Plant Macrofossils ◽  
Early Pleistocene ◽  
Last Interglacial ◽  
Stratigraphic Record ◽  
History Of ◽  
And Behavior

Understanding the history of the Greenland Ice Sheet (GrIS) is critical for determining its sensitivity to warming and contribution to sea level; however, that history is poorly known before the last interglacial. Most knowledge comes from interpretation of marine sediment, an indirect record of past ice-sheet extent and behavior. Subglacial sediment and rock, retrieved at the base of ice cores, provide terrestrial evidence for GrIS behavior during the Pleistocene. Here, we use multiple methods to determine GrIS history from subglacial sediment at the base of the Camp Century ice core collected in 1966. This material contains a stratigraphic record of glaciation and vegetation in northwestern Greenland spanning the Pleistocene. Enriched stable isotopes of pore-ice suggest precipitation at lower elevations implying ice-sheet absence. Plant macrofossils and biomarkers in the sediment indicate that paleo-ecosystems from previous interglacial periods are preserved beneath the GrIS. Cosmogenic 26Al/10Be and luminescence data bracket the burial of the lower-most sediment between <3.2 ± 0.4 Ma and >0.7 to 1.4 Ma. In the upper-most sediment, cosmogenic 26Al/10Be data require exposure within the last 1.0 ± 0.1 My. The unique subglacial sedimentary record from Camp Century documents at least two episodes of ice-free, vegetated conditions, each followed by glaciation. The lower sediment derives from an Early Pleistocene GrIS advance. 26Al/10Be ratios in the upper-most sediment match those in subglacial bedrock from central Greenland, suggesting similar ice-cover histories across the GrIS. We conclude that the GrIS persisted through much of the Pleistocene but melted and reformed at least once since 1.1 Ma.

scholarly journals Quaternary observations in southern Peary Land, North Greenland

1976 ◽  
Vol 80 ◽  
pp. 15-17
Author(s):  
A Weidick
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Primary Objective ◽  
Drilling Operation ◽  
Ice Cap ◽  
History Of ◽  
Quaternary History ◽  
Work Done ◽  
North Greenland

A geological group consisting of the author and P. R.Dawes accompanied the 1975 Greenland Ice Sheet Programme's (GISP) ice drilling operation at Hans Tavsens Iskappe, south-westem Peary Land. The primary objective of the group was to investigate the Quaternary history of the area south of the ice cap as a supplement to the work done elsewhere in Peary Land by the various Peary Land Expeditions (Troelsen, 1952; Kirkeby, 1963: Fredskild, 1969), Operations Groundhog and Lead Dog (Stoertz & Needleman, 1957; Davies, 1972; Ahnert, 1960) and the British Joint Services Expedition (Dawes, 1970).

scholarly journals How warm was Greenland during the last interglacial period?

2016 ◽  
Vol 12 (9) ◽  
pp. 1933-1948 ◽  
Author(s):  
Amaelle Landais ◽  
Valérie Masson-Delmotte ◽  
Emilie Capron ◽  
Petra M. Langebroek ◽  
Pepijn Bakker ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Water Isotopes ◽  
Interglacial Period ◽  
Last Interglacial ◽  
Last Interglacial Period ◽  
Ice Sheet Topography ◽  
North Greenland

Abstract. The last interglacial period (LIG, ∼ 129–116 thousand years ago) provides the most recent case study of multimillennial polar warming above the preindustrial level and a response of the Greenland and Antarctic ice sheets to this warming, as well as a test bed for climate and ice sheet models. Past changes in Greenland ice sheet thickness and surface temperature during this period were recently derived from the North Greenland Eemian Ice Drilling (NEEM) ice core records, northwest Greenland. The NEEM paradox has emerged from an estimated large local warming above the preindustrial level (7.5 ± 1.8 °C at the deposition site 126 kyr ago without correction for any overall ice sheet altitude changes between the LIG and the preindustrial period) based on water isotopes, together with limited local ice thinning, suggesting more resilience of the real Greenland ice sheet than shown in some ice sheet models. Here, we provide an independent assessment of the average LIG Greenland surface warming using ice core air isotopic composition (δ15N) and relationships between accumulation rate and temperature. The LIG surface temperature at the upstream NEEM deposition site without ice sheet altitude correction is estimated to be warmer by +8.5 ± 2.5 °C compared to the preindustrial period. This temperature estimate is consistent with the 7.5 ± 1.8 °C warming initially determined from NEEM water isotopes but at the upper end of the preindustrial period to LIG temperature difference of +5.2 ± 2.3 °C obtained at the NGRIP (North Greenland Ice Core Project) site by the same method. Climate simulations performed with present-day ice sheet topography lead in general to a warming smaller than reconstructed, but sensitivity tests show that larger amplitudes (up to 5 °C) are produced in response to prescribed changes in sea ice extent and ice sheet topography.

scholarly journals Late Pliocene Cordilleran Ice Sheet development with warm northeast Pacific sea surface temperatures

2020 ◽  
Vol 16 (1) ◽  
pp. 299-313 ◽  
Author(s):  
Maria Luisa Sánchez-Montes ◽  
Erin L. McClymont ◽  
Jeremy M. Lloyd ◽  
Juliane Müller ◽  
Ellen A. Cowan ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Ice Sheet ◽  
Gulf Of Alaska ◽  
Sea Surface ◽  
Early Pleistocene ◽  
Late Pliocene ◽  
Subarctic Pacific ◽  
Cordilleran Ice Sheet ◽  
Forcing Mechanisms ◽  
Atmospheric Co2 Concentrations

Abstract. The initiation and evolution of the Cordilleran Ice Sheet are relatively poorly constrained. International Ocean Discovery Program (IODP) Expedition 341 recovered marine sediments at Site U1417 in the Gulf of Alaska (GOA). Here we present alkenone-derived sea surface temperature (SST) analyses alongside ice-rafted debris (IRD), terrigenous, and marine organic matter inputs to the GOA through the late Pliocene and early Pleistocene. The first IRD contribution from tidewater glaciers in southwest Alaska is recorded at 2.9 Ma, indicating that the Cordilleran Ice Sheet extent increased in the late Pliocene. A higher occurrence of IRD and higher sedimentation rates in the GOA during the early Pleistocene, at 2.5 Ma, occur in synchrony with SSTs warming on the order of 1 ∘C relative to the Pliocene. All records show a high degree of variability in the early Pleistocene, indicating highly efficient ocean–climate–ice interactions through warm SST–ocean evaporation–orographic precipitation–ice growth mechanisms. A climatic shift towards ocean circulation in the subarctic Pacific similar to the pattern observed during negative Pacific Decadal Oscillation (PDO) conditions today occurs with the development of more extensive Cordilleran glaciation and may have played a role through increased moisture supply to the subarctic Pacific. The drop in atmospheric CO2 concentrations since 2.8 Ma is suggested as one of the main forcing mechanisms driving the Cordilleran glaciation.

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