scholarly journals Palaeolake sediment records reveal a mid‐ to late Younger Dryas ice‐sheet maximum in Mid‐Norway

Boreas ◽  
2021 ◽  
Author(s):  
Fredrik Høgaas ◽  
Simon A. Larsson ◽  
Martin Klug ◽  
Lars Olsen ◽  
Stefan Wastegård
Keyword(s):  
Ice Sheet ◽  
Younger Dryas ◽  
Sediment Records

scholarly journals Comparing a thermo-mechanical Weichselian ice sheet reconstruction to GIA driven reconstructions: aspects of earth response and ice configuration

2013 ◽  
Vol 5 (2) ◽  
pp. 2345-2388 ◽  
Author(s):  
P. Schmidt ◽  
B. Lund ◽  
J-O. Näslund
Keyword(s):  
Sea Level ◽  
Ice Sheet ◽  
Younger Dryas ◽  
Slow Phase ◽  
Glacial Isostatic Adjustment ◽  
Relative Sea Level ◽  
Isostatic Adjustment ◽  
Earth Models ◽  
Uplift Rates ◽  
Best Fit

Abstract. In this study we compare a recent reconstruction of the Weichselian ice-sheet as simulated by the University of Main ice-sheet model (UMISM) to two reconstructions commonly used in glacial isostatic adjustment (GIA) modeling: ICE-5G and ANU (also known as RSES). The UMISM reconstruction is carried out on a regional scale based on thermo-mechanical modelling whereas ANU and ICE-5G are global models based on the sea-level equation. The Weichselian ice-sheet in the three models are compared directly in terms of ice volume, extent and thickness, as well as in terms of predicted glacial isostatic adjustment in Fennoscandia. The three reconstructions display significant differences. UMISM and ANU includes phases of pronounced advance and retreat prior to the last glacial maximum (LGM), whereas the thickness and areal extent of the ICE-5G ice-sheet is more or less constant up until LGM. The final retreat of the ice-sheet initiates at earliest time in ICE-5G and latest in UMISM, while ice free conditions are reached earliest in UMISM and latest in ICE-5G. The post-LGM deglaciation style also differs notably between the ice models. While the UMISM simulation includes two temporary halts in the deglaciation, the later during the Younger Dryas, ANU only includes a decreased deglaciation rate during Younger Dryas and ICE-5G retreats at a relatively constant pace after an initial slow phase. Moreover, ANU and ICE-5G melt relatively uniformly over the entire ice-sheet in contrast to UMISM which melts preferentially from the edges. We find that all three reconstructions fit the present day uplift rates over Fennoscandia and the observed relative sea-level curve along the Ångerman river equally well, albeit with different optimal earth model parameters. Given identical earth models, ICE-5G predicts the fastest present day uplift rates and ANU the slowest, ANU also prefers the thinnest lithosphere. Moreover, only for ANU can a unique best fit model be determined. For UMISM and ICE-5G there is a range of earth models that can reproduce the present day uplift rates equally well. This is understood from the higher present day uplift rates predicted by ICE-5G and UMISM, which results in a bifurcation in the best fit mantle viscosity. Comparison of the uplift histories predicted by the ice-sheets indicate that inclusion of relative sea-level data in the data fit can reduce the observed ambiguity. We study the areal distributions of present day residual surface velocities in Fennoscandia and show that all three reconstructions generally over-predict velocities in southwestern Fennoscandia and that there are large differences in the fit to the observational data in Finland and northernmost Sweden and Norway. These difference may provide input to further enhancements of the ice-sheet reconstructions.

scholarly journals Deglaciation and ice shelf development at the northeast margin of the Laurentide Ice Sheet during the Younger Dryas chronozone

Boreas ◽  
2017 ◽  
Vol 47 (1) ◽  
pp. 271-296 ◽  
Author(s):  
Mark F. A. Furze ◽  
Anna J. Pieńkowski ◽  
Morgan A. McNeely ◽  
Robbie Bennett ◽  
Alix G. Cage
Keyword(s):  
Ice Sheet ◽  
Younger Dryas ◽  
Laurentide Ice Sheet ◽  
Ice Shelf

scholarly journals Routing of meltwater from the Laurentide Ice Sheet during the Younger Dryas cold episode

Nature ◽  
1989 ◽  
Vol 341 (6240) ◽  
pp. 318-321 ◽  
Author(s):  
Wallace S. Broecker ◽  
James P. Kennett ◽  
Benjamin P. Flower ◽  
James T. Teller ◽  
Sue Trumbore ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Younger Dryas ◽  
Laurentide Ice Sheet ◽  
Cold Episode

scholarly journals Younger Dryas Interval and outflow from the Laurentide Ice Sheet

2000 ◽  
Vol 15 (1) ◽  
pp. 4-18 ◽  
Author(s):  
T. C. Moore ◽  
J. C. G. Walker ◽  
D. K. Rea ◽  
C. F. M. Lewis ◽  
L. C. K. Shane ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Younger Dryas ◽  
Laurentide Ice Sheet

Tephrochronological evidence of a later Younger Dryas ice-sheet maximum in central Norway

2021 ◽  
Author(s):  
Simon A. Larsson ◽  
Stefan Wastegård ◽  
Fredrik Høgaas
Keyword(s):  
Radiocarbon Dating ◽  
Ice Sheet ◽  
Younger Dryas ◽  
Coastal Lake ◽  
Cold Event ◽  
Western Norway ◽  
Scandinavian Ice Sheet ◽  
Marine Fossils ◽  
Ice Sheet Dynamics ◽  
Southern Norway

<p>The Scandinavian Ice Sheet responded time-transgressively to the Younger Dryas (Greenland Stadial 1) cold event with large regional variations. Around Trondheimsfjorden in central Norway, the Tautra Moraines and the Hoklingen Moraines have long been assumed to have formed by glacial readvances during this event, as they have been dated to c. 12.7 and 11.6 cal. ka BP respectively (Olsen et al., 2015), mainly based on radiocarbon dating of often marine fossils. The Tautra Moraines, being the outer ridges of the two, should thus represent the maximum ice-sheet extent in this region during the Younger Dryas.</p><p>This ice-front position established a pro-glacial lake west of present-day Leksvik village on the Fosen peninsula (Selnes, 1982), which covered the Lomtjønnin lakes and Lomtjønnmyran fens, and drained through a spillway via Lake Rørtjønna. Some 20 km inland (northeast) from this location, inside the Tautra Moraines, the location of the Damåsmyran bog was covered by the ice sheet at that time.</p><p>By examining sediments from these sites for occurrences of volcanic ashes (visible and cryptotephra), combined with radiocarbon dating, we find that the ice front remained at the Tautra Moraines until the late Younger Dryas, contrary to the previous chronology (and overriding the suggested formation age of the Hoklingen Moraines). These findings comply with several recent reconstructions of the deglaciation at other sites in western (Lohne et al., 2012; Mangerud et al., 2016) and southern Norway (Romundset et al., 2019) and are a strong example of the usefulness of tephrochronology in the reconstruction of past ice-sheet dynamics.</p><p> </p><p><strong>References</strong></p><p>Lohne, Ø.S., Mangerud, J. & Svendsen, J.I. (2012) Timing of the Younger Dryas glacial maximum in Western Norway. <em>Journal of Quaternary Science</em>, vol. 27, pp. 81–88.</p><p>Mangerud, J., Aarseth, I., et al. (2016) A major re-growth of the Scandinavian Ice Sheet in western Norway during Allerød–Younger Dryas. <em>Quaternary Science Reviews</em>, vol. 132, pp. 175–205.</p><p>Olsen, L., Høgaas, F. & Sveian, H. (2015) Age of the Younger Dryas ice-marginal substages in Mid-Norway—Tautra and Hoklingen, based on a compilation of 14C-dates. <em>Norges geologiske undersøkelse Bulletin</em>, vol. 454, pp. 1–13.</p><p>Romundset, A., Lakeman, T.R. & Høgaas, F. (2019) Coastal lake records add constraints to the age and magnitude of the Younger Dryas ice-front oscillation along the Skagerrak coastline in southern Norway. <em>Journal of Quaternary Science</em>, vol. 34, pp. 112–124.</p><p>Selnes, H. (1982) Paleo-økologiske undersøkelser omkring israndavsetninger på Fosenhalvøya, Midt-Norge. Thesis at the Department of Botany, University of Trondheim.</p>

scholarly journals The deglaciation of coastal areas of southeast Greenland

The Holocene ◽  
2018 ◽  
Vol 28 (9) ◽  
pp. 1535-1544 ◽  
Author(s):  
Laurence M Dyke ◽  
Anna LC Hughes ◽  
Camilla S Andresen ◽  
Tavi Murray ◽  
John F Hiemstra ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Younger Dryas ◽  
Greenland Ice Sheet ◽  
Coastal Areas ◽  
Glacial Cycle ◽  
Last Glacial ◽  
The North ◽  
Exposure Ages ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Large marine-terminating glaciers around the margins of the Greenland Ice Sheet have retreated, accelerated and thinned over the last two decades. Relatively little is known about the longer term behaviour of the Greenland Ice Sheet, yet this information is valuable for assessing the significance of modern changes. We address this by reporting 11 new beryllium-10 (10Be) exposure ages from previously uninvestigated coastal areas across southeast Greenland. The new ages are combined with existing data from the region to assess the timing of glacier retreat after the Last Glacial Maximum. The results show that deglaciation occurred first in the north of the region (~68°N) and progressed southwards. This north–south progression is attributed to the influence of the warm Irminger Current on the ice margin. Areas in the south of the region were isolated from the warm waters by the shallow bathymetry of the continental shelf. This demonstrates that oceanographic forcing paced the deglaciation of southeast Greenland through the Younger Dryas and early Holocene. In most areas of southeast Greenland bedrock ages are systematically older than their counterpart boulder samples; this offset is likely the result of inherited 10Be content in bedrock surfaces. This suggests that subglacial erosion during the last glacial cycle was insufficient to completely remove pre-existing 10Be content. Alternatively, this pattern may be the signature of a substantial retreat and advance cycle prior to final Holocene deglaciation.

Reconstructing the Cordilleran Ice Sheet in northern British Columbia during the Late Pleistocene climate reversals

2020 ◽  
Author(s):  
Helen Dulfer ◽  
Martin Margold
Keyword(s):  
British Columbia ◽  
Late Pleistocene ◽  
Regional Scale ◽  
Ice Sheet ◽  
Younger Dryas ◽  
Western Canada ◽  
Alpine Glaciers ◽  
Pleistocene Climate ◽  
Cordilleran Ice Sheet ◽  
Exposure Ages

<p>The Cordilleran Ice Sheet (CIS) repeatedly covered western Canada during the Pleistocene and attained a volume and area similar to that of the present-day Greenland Ice Sheet. Deglaciation of the CIS following the Last Glacial Maximum (LGM) directly affected atmosphere and ocean circulation, eustatic sea level, and human migration from Asia to North America. It has recently been shown that the rapid climate oscillations at the end of the Pleistocene had a dramatic effect on the CIS. Data on glacial isostatic adjustment and cosmogenic nuclide exposure ages indicate that abrupt warming at the onset of the Bølling-Allerød caused significant thinning of the ice sheet, resulting in a fifty percent reduction in mass, while the Younger Dryas cooling caused the expansion of alpine glaciers across the mountains of western Canada. However, the mountainous subglacial terrain makes it challenging to reconstruct the regional-scale deglaciation dynamics of the ice sheet, and its configuration during this period of rapid change remains poorly constrained. </p><p>Here we use the glacial landform record to reconstruct the ice sheet configuration for the central sector of the CIS, over the Cassiar and Omineca Mountains in northern British Columbia, during the Late Pleistocene climate reversals. We present the first regional-scale reconstruction of the CIS following the Bølling-Allerød warming, whereby the ice sheet was reduced to a labyrinth of valley glaciers fed by ice dispersal centres located over the Skeena Mountains in the south and Coast Mountains in the west. Additionally, numerous lateral and terminal late glacial moraines delineate the extent of alpine glaciers, ice caps and ice fields that regrew on mountain peaks above the CIS during the Younger Dryas. Cross-cutting relationships indicate that the valley glaciers of the CIS were slower to respond to the Younger Dryas cooling than the mountain glaciers.</p>

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