Geomorphological record and equilibrium line altitude of glaciers during the last glacial maximum in the Rodna Mountains (eastern Carpathians)

2020 ◽  
pp. 1-20
Author(s):  
Piotr Kłapyta ◽  
Marcel Mîndrescu ◽  
Jerzy Zasadni

Abstract In the eastern Carpathians the legacy of glaciation is preserved in several isolated mountain massifs. This paper presents new mapping results of glaciated valley land systems in the Rodna Mountains, the highest part of the eastern Carpathians (2303 m above seal level). In most of the glacial valleys, the maximal Pleistocene extent is marked by freshly shaped moraines, which are referred in this study as the Pietroasa glacial stage and regarded as the last glacial maximum (LGM) advance. Only in three valleys do older Şesura glacial stage moraines (pre-LGM, likely Marine Oxygen Isotope Stage 6) occur. On the basis of the geomorphological record, we reconstruct the extent, surface geometry, and equilibrium line altitude (ELA) of Pietroasa-stage glaciers. The local ELA pattern of north-exposed glaciers in the Rodna Mountains shows a rising trend towards the southeast, which suggests dominant snow-bearing winds and orographically induced precipitation from the west. This finding fits well with the dominant palaeo-wind direction inferred from other Carpathian proxies and confirms the dominance of zonal circulation pattern during the global LGM in central eastern Europe.

1998 ◽  
Vol 48 (1) ◽  
pp. 23-37 ◽  
Author(s):  
Duri Florineth

Abstract. Using detailed field evidence provided by trimlines on former nunataks, erratic boulders and the orientations of glacial striae, the surface geometry in the accumulation area during the Last Glacial Maximum was reconstructed for the area of SE Switzerland and adjacent Italy. Collectively, the trends of trimline elevations, flowlines deduced from glacial striae and bedrock morphology along the longitudinal valleys and their tributaries indicate that the former accumulation area consisted of an ice dome with the ice divide located over the area enclosed by Schlarignia, Cinuos-chel, Livigno and Piz Bernina. It attained a minimum altitude of approximately 3000 m. Modelling the topography of the ice surface using a Geographical Information System (GIS) is consistent with these results. The paleoclimatological signal included in this surface geometry was used to draw conclusions about the main atmospheric paleocireulation patterns and to outline the principal precipitation areas for the Alps during the last glaciation. It followed from this that ice build-up was principally related to dominating precipitation by southerly circulation (foehn). The prevaleance of foehn circulation most likely reflects a southward shift of the North Atlantic polar atmospheric front and of the accompanied storm track due to the advancing margin of sea ice. There exists good agreement between these assumptions and (a) results of global circulation models for the time of the LGM; (b) estimations of basal shear stress values and flow velocities for Ice Age glaciers; and (c) interpretations of paleowind indicators.


1994 ◽  
Vol 42 (1) ◽  
pp. 1-19 ◽  
Author(s):  
Nick Hulton ◽  
David Sugden ◽  
Antony Payne ◽  
Chalmers Clapperton

AbstractIce cap modeling constrained by empirical studies provides an effective way of reconstructing past climates. The former Patagonian ice sheet is in a climatically significant location since it lies athwart the Southern Hemisphere westerlies and responds to the latitudinal migration of climatic belts during glacial cycles. A numerical model of the Patagonian ice cap for the last glacial maximum (LGM) is developed, which is time-dependent and driven by changing the mass balance/altitude relationship. It relies on a vertically integrated continuity model of ice mass solved over a finite difference grid. The model is relatively insensitive to ice flow parameters but highly sensitive to mass balance. The climatic input is adjusted to produce the best fit with the known limits of the ice cap at the LGM. The ice cap extends 1800 km along the Andes and has a volume of 440,000 km3. During the LGM the equilibrium line altitude (ELA) was lower than at present by at least 560 m near latitude 40°S, 160 m near latitude 50°S, and 360 m near latitude 56°S. The latitudinal variation in ELA depression can be explained by an overall fall in temperature of about 3.0°C and the northward migration of precipitation belts by about 5° latitude. Annual precipitation totals may have decreased by about 0.7 m at latitude 50°S and increased by about 0.7 m at latitude 40°S. The ELA rises steeply by up to 4 m per kilometer from west to east as the westerlies cross the Andes and this prevents ice growth to the east. The limited decrease in temperature during the LGM could be related to the modest migration of the Antarctic convergence between South America and the Antarctic Peninsula.


2005 ◽  
Vol 20 (7-8) ◽  
pp. 821-838 ◽  
Author(s):  
Nicholas L. Balascio ◽  
Darrell S. Kaufman ◽  
William F. Manley

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