Glacier fluctuations, equilibrium-line altitudes and palaeoclimate in Lyngen, northern Norway, during the Lateglacial and Holocene

Abstract

Abstract:Based on lacustrine and morpho-stratigraphical evidence from Lyngen in Troms, northern Norway, thirteen marginal moraines have been mapped and dated in front of Lenangsbreene in Strupskardet. Moraines M1-M3 and M8-M9 are suggested orginally to be formed as ice-cored moraines, whereas M4-M7 and M10-M13 are suggested to be push and and melt-out moraines. A chronological framework, taking into account a combination of relict periglacial features, former shorelines and related glacier-meltwater channels, lichenometry, and AMS radiocarbon dated lacustrine sediments spanning the last 20,000 cal. yr BP, has been established. The proglacial lake Aspvatnet was isolated from the sea c. 10,300 cal. yr BP, and the lacustrine sediments have been investigated by use of LOI at 550/950ºC, magnetic susceptibility, water content, wet-and dry bulk density (DBD), and the magnetic parameters anhysteretic remanent magnetisation (ARM) and saturation remanent magnetisation (SIRM). There is in general good agreement between physical sediment parameters and magnetic parameters. DBD, a combination of medium and fine silt and the two statistical parameters 'sorting' and 'mean' have been used to construct a high-resolution glacier-fluctuation curve for the last 3800 cal. yr BP. Based on an accumulation-area ratio (AAR) of 0.6 and an adapted 'Little Ice Age ratio' (LR) approach, a continuous temperature-precipitation-wind equilibriumline altitude (TPW-ELA) curve for the last 20,000 cal. yr BP have been constructed. Using an established exponential relationship between mean ablation-season temperature and mean annual solid precipitation at the ELA of Norwegian glaciers, variations in mean winter precipitation as snow are quantified using an independent proxy for summer temperature. Mean annual winter precipitation varied from 500 to 5000 mm water equivalents, and on average, Holocene estimates is c. 50% higher than similar figures from the Lateglacial. The two driest periods occurred during Heinrich events 1 (H1) (17,500-16,500) and 0 (H0) (13,(0)(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)200), whereas freshwater pulses to the North Atlantic had apparently no systematic impact on mean winter precipitation. Based on the winter precipitation curve from Lyngen, the atmospheric circulation responded to the SST lowering associated with H1 and H0 events in Lyngen with formation of talusderived rock glaciers at sea level.

Paleoclimate changes inferred from stable isotopes and magnetic properties of organic-rich lake sediments in Arctic Norway

“…We also interpret these two shifts to indicate wetter winter conditions which might have been related to large-scale atmospheric circulation anomalies. This interpretation is in good accordance with results from northern Fennoscandia (Vorren et al 2007;Bakke et al 2005;Paasche et al 2004Paasche et al , 2007a.…”

New Aspects of High-Mountain Palaeobiogeography: A Synthesis of Data from Forefields of Receding Glaciers and Ice Patches in the Tärna and Kebnekaise Mountains, Swedish Lapland

“…This situation prevailed throughout most (or all) of the period 9530 -4480 cal yr BP, as inferred also in other studies in Scandinavia (e.g., Rosqvist and Østrem, 1989;Bakke et al, 2005;Nesje et al, 2008;Öberg and Kullman, 2011a). It is reasonable to conclude that this circumstance reflects a hemispheric climatic situation related to higher-than-present insolation levels, forced largely by the Earth's orbital variations (Ekholm, 1901;Berger and Loutre, 1991).…”

Further Details on Holocene Treeline, Glacier/Ice Patch and Climate History in Swedish Lapland

“…yr BP, suggests that the concerned glacier, like many others, did not exist prior to that date (cf. Bakke et al 2005). Dated peat remains indicated that neoglacial instatement of this particular glacier ice took place after 3890 cal.…”