Several glacier advances
During and immediately after the end of the last ice age, about 11,000 years ago, abrupt, decadal- to centennial-scale climate variations caused significant glacier variations in Norway. Increased freshwater inflow to the North Atlantic and Arctic Oceans has been suggested as one of the most likely mechanisms to explain the abrupt and significant climatic events during that time in NW Europe.
The glaciers melted away
The studied Norwegian glaciers apparently melted away at least once during the early/mid-Holocene (the period after the last ice age). The time interval with the most contracted glaciers in Scandinavia was between 6600 and 6000 years ago. Subsequently the glaciers started to advance and regionally high glacier activity are recorded at about ~5600, 4400, 3300, 2300, and 1600 years ago, and during the ‘Little Ice Age’. Times with overall less glacier activity in Norway were apparently around 5000, 4000, 3000, 2000, and 1200 years ago. It has been proposed in previous studies that a larger number of glacier advances occurred in northern Sweden than in southern Norway during the mid Holocene. Evidence for the previously suggested glacier advances in northern Scandinavia has, however, been questioned by more recent, multi-disciplinary studies.
The ‘Little Ice Age’
Most Norwegian glaciers attained their maximum ‘Little Ice Age’ extent during the mid-18th century. Cumulative glacier length variations in southern Norway show an overall retreat from the mid-18th century until the 1930s-40s. Subsequently, most Norwegian glaciers retreated significantly. Maritime outlet glaciers with short frontal time lags (<10-15 years) started to advance in the mid-1950s, whereas long outlet glaciers with longer frontal time lags (>15-20 years) continued their retreat until the 1970s and 1980s. However, maritime glaciers started to advance as a response to higher winter accumulation during the first part of the 1990s. After 2000, several of the Norwegian glaciers have retreated remarkably fast (annual frontal retreat >100 m) mainly due to high summer temperatures.
What caused these climate and glacier variations?
The general glacier retreat during the early Holocene and the advances starting about 6000 years ago are in line with orbital forcing, due to decrease of Northern Hemisphere summer solar insolation and increase in winter solar insolation. In addition, regional weather modes, such as the North Atlantic Oscillation and the Arctic Oscillation, together with solar-activity changes and volcanic eruptions, play a significant role with respect to decadal and multi-decadal climate variability.
Reference:
Nesje, A. a) b) (2009): Latest Pleistocene and Holocene alpine glacier fluctuations in Scandinavia, Quaternary Science Reviews.
a) Department of Earth Science, University of Bergen, Allégaten 41, N-5007 Bergen, Norway
b) Bjerknes Centre for Climate Research, Allégaten 55, N-5007 Bergen, Norway