Reconstruction of the glacier dynamics and Holocene chronology of retreat of Helagsglaciären in Central Sweden

Abstract

Despite significant efforts to reconstruct the Holocene glacial history in Scandinavia, evidence of glacier fluctuations in Sweden has mostly been limited to palaeoclimatic proxies, while dating of direct geological evidence from glacier forelands is still rare. This is the first study in Sweden that has attempted to fully reconstruct dynamics, chronology and palaeoclimate of a glacier throughout the Holocene by applying geomorphological mapping, sedimentology, lichenometry and Equilbrium Line Altitude (ELA) calculation on Helagsglaciären, Sweden’s southernmost glacier. Helags valley is occupied by extensive glacial and associated sediments of different ages far beyond the current extent of the glacier, indicating earlier prominent advances dated here to 8.5–8.0 ka, around 1.2–1.0 ka and around 1789 CE, which represents the Little Ice Age (LIA) maximum. During the Holocene, the glacier switched from a polythermal regime with frozen bed at the thinning ice margin and parts of the tongue to a fully temperate one. Today, its southern part remains active and temperate, while the northern is probably cold-based. Using calculated ELAs, the climate during the 8.5–8.0 ka event was reconstructed to be cold and wet; slightly colder and drier during the 1.2–1.0 ka advance; and coldest and driest during the LIA. This agrees well with other paleoclimate and glacier fluctuation reconstructions from Scandinavia. In conclusion, this study demonstrates a wealth of information on past glacier dynamics and palaeoclimate that can be reconstructed from current small cirque glaciers in the Swedish Scandinavian Mountains, highlighting the need to study them more extensively.