Glacier fluctuation and inferred climatology of Langjökull ice cap through the Little Ice Age

• Published in: Quaternary science reviews 2007-10, Vol.26 (19), p.2337-2353
• Main Authors: Flowers, Gwenn E., Björnsson, Helgi, Geirsdóttir, Áslaug, Miller, Gifford H., Clarke, Garry K.C.
• Format: Article
• Language: English
• ISSN: 0277-3791; 1873-457X
• DOI: 10.1016/j.quascirev.2007.07.016

Emerging paleoclimate records from proglacial lake Hvítárvatn, central Iceland, suggest that Langjökull ice cap attained its maximum Holocene extent within the last 400 years. With the aim of constructing glaciological models and appropriate model inputs for Holocene simulations of Langjökull, we begin by simulating the evolution of Langjökull through the Little Ice Age to present, a period for which we have some constraint on ice-cap geometry. Using modern measured mass balance distributions (1997–2003) and meteorological data from nearby Hveravellir, we derive a reference precipitation field for the period 1961–1990 over the ice cap. Our simulations suggest Langjökull attained its maximum Little Ice Age volume around 1840 with a second local maximum around 1890. The two outlet glaciers terminating in Hvítárvatn, Nor ð urjökull and Su ð urjökull, advance slowly into the lake, occupying their maximum lake area in the late 19th century, and retreat comparatively rapidly in the mid- to late 20th century. Simulations of Nor ð urjökull are much more faithful to the geomorphic evidence than are simulations of Su ð urjökull, potentially suggesting a difference in dynamics between these two glaciers. While only 35% of the Hvítárvatn catchment area is ice-covered, meltwater from Langjökull comprises ∼ 70 % of the water input to the lake. Two-thirds of this input from the ice cap is transported as groundwater. Simulated glacier-derived discharge to the lake through the Little Ice Age suggests that a sediment concentration of 1.5 kg m - 3 would have resulted in the transport of 1.5 × 10 11 kg of material to the lake over the last 300 years, comparable to the estimated mass of sediment in the most recently deposited sedimentary unit in the lake.