Holocene dynamics of Arsine Glacier (Ecrins Massif, French Alps) inferred from cosmogenic 10Be dating (original) (raw)
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2022
Climate is currently warming due to anthropogenic impact on the Earth’s atmosphere. To better understand the processes and feedbacks within the climate system that underlie this accelerating warming trend, it is useful to examine past periods of abrupt climate change that were driven by natural forcings. Glaciers provide an excellent natural laboratory for reconstructing the climate of the past as they respond sensitively to climate oscillations. Therefore, we study glacier systems and their behavior during the transition from colder to warmer climate episodes, focusing on the period between 15 and 10 ka. Using a combination of geomorphological mapping and beryllium-10 surface exposure dating, we reconstruct ice extents in two glaciated valleys of the Silvretta Massif in the Austrian Alps and find that the general ice retreat during the deglaciation after the Last Glacial Maximum (LGM) was interrupted by glacier stabilization during the Oldest Dryas to Bølling transition (moraine ag...
A Younger Dryas re-advance of local glaciers in north Greenland
Quaternary Science Reviews, 2015
The Younger Dryas (YD) is a well-constrained cold event from 12,900 to 11,700 years ago but it remains unclear how the cooling and subsequent abrupt warming recorded in ice cores was translated into ice margin fluctuations in Greenland. Here we present 10 Be surface exposure ages from three moraines in front of local glaciers on a 50 km stretch along the north coast of Greenland, facing the Arctic Ocean. Ten ages range from 11.6 ± 0.5 to 27.2 ± 0.9 ka with a mean age of 12.5 ± 0.7 ka after exclusion of two outliers. We consider this to be a minimum age for the abandonment of the moraines. The ages of the moraines are furthermore constrained using Optically Stimulated Luminescence (OSL) dating of epishelf sediments, which were deposited prior to the ice advance that formed the moraines, yielding a maximum age of 12.4 ± 0.6 ka, and bracketing the formation and subsequent abandonment of the moraines to within the interval 11.8-13.0 ka ago. This is the first time a synchronous YD glacier advance and subsequent retreat has been recorded for several independent glaciers in Greenland. In most other areas, there is no evidence for re-advance and glaciers were retreating during YD. We explain the different behaviour of the glaciers in northernmost Greenland as a function of their remoteness from the Atlantic Meridional Overturning Circulation (AMOC), which in other areas has been held responsible for modifying the YD drop in temperatures. *Manuscript Click here to view linked References
Late Glacial mountain glacier culmination in Arctic Norway prior to the Younger Dryas
Quaternary Science Reviews, 2020
Climate changes during the Late Glacial period (LG; 15-11 ka) as recorded in Greenland and Antarctic ice cores show a bipolar pattern. Between 14.5 ka and 13 ka ago, the northern latitudes experienced the Bølling/Allerød (BA) warm period, while southern records feature the Antarctic Cold Reversal (ACR). Between 12.9 ka and 11.7 ka ago, the north was under the Younger Dryas (YD) cold spell while southern latitude temperature rose in parallel to atmospheric CO2 concentrations. While the southern hemisphere pattern is well documented in mountain glacier moraine records from New Zealand and Patagonia, in northern mid-latitudes and the Arctic, the LG glacier culmination has been connected to the YD stadial, apparently confirming the bipolar pattern. We present a geomorphic map of mountain glaciers in Arctic Norway, a cosmogenic nuclide chronology from 71 moraine boulders from the LG and the Holocene, and first-order glacier modeling experiments. The model and dating results show that the studied mountain glaciers are most sensitive to summer-temperature change, that their response to those changes is highly correlated to a wider region and that these mountain glaciers in Arctic Norway reached their maximum LG extent about 14 ka ago, prior to the YD. Following considerable retreat through the first part of the YD, glaciers re-stabilized in the mid-YD and showed slower oscillatory retreat through the latter part of the YD. We compare this glacier pattern to updated earlier glacier records in the wider Arctic and North Atlantic region and propose a pattern of coherent glacier response to climate changes during this interval. The LG results from Arctic glaciers show consistency to the glacier record from New Zealand and Patagonia. This first-order interhemispheric coherency of LG mountain glacier fluctuations driven mainly by summer temperature would support the view that the bipolar seesaw was primarily a northern winter phenomenon during the LG period, and the YD in particular. More similar experiments need to be performed to further test this scenario.
Climatic fluctuations of glaciers of the Little Ice Age (LIA)-rank used to show comparable magnitudes during the Holocene. That is why the extent of maximal LIA moraines in the Alps attains similar position as those of the previous LIA-type Holocene advances. Consequently, the LIA moraines represent a massive and frequently multi-ridge depositional system. Certain differences in reaction to climatic changes and in moraine development result from the glacier size, percentage of debris-covered ice surfaces, and topography of alimentary areas. Such differences are particularly spectacular regarding "pure ice" and debris-covered glaciers. Another system represent rock glaciers which, however, frequently accompany regular glaciers. Some rock glaciers originated due to one-time transformation of a "glacial" glacier during its recession, while others formed owing to long-term accumulation of rock debris within glacial cirques during successive oscillations of small cirque glaciers in the Holocene, given suitable topographic and topoclimatic conditions. The relationship between the ELA and altitude of cirque bottom and/or debris supply from surrounding walls is of key importance in this case.
The Open Geography Journal, 2011
To exploit the potential of rock glaciers as indicators of past climate condition it is first necessary to date them. The combined application of both relative and absolute dating techniques is a promising approach. In this study, we present Schmidt-hammer rebound value measurements and weathering rind thicknesses on four active and one relict rock glacier in the Albula area of the eastern Swiss Alps. Associated landforms such as the moraines in front of rock glaciers and glacially polished bedrock also were used to set up the temporal framework. This was done using soil chemical analyses, radiocarbon dating of the stable fraction of soil organic matter and surface exposure dating of boulders. Schmidt-hammer and weathering rind measurements showed, in most cases, well-pronounced trends with increasing surface ages. These values are in line with measurements from other nearby rock glaciers with comparable lithologies. Use of this information together with the numeric ages makes it possible to derive two main activity phases: one started soon after the ice retreat following the Younger Dryas, the main activity occurred most likely in the early Holocene and lasted approximately until the Holocene climate optimum. The second activity phase continues today and had an unclear start between 10 to 6 cal ky BP.