High-Resolution Modeling of the Advance of the Younger Dryas Ice Sheet and Its Climate in Scotland

• Published in: Quaternary Research
• Main Author: Hubbard, Alun
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1999
• Subjects: Ben Nevis; Ice Sheet
• Online Access: http://dx.doi.org/10.1006/qres.1999.2055; http://api.elsevier.com/content/article/PII:S0033589499920550?httpAccept=text/xml; http://api.elsevier.com/content/article/PII:S0033589499920550?httpAccept=text/plain; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033589400025618

Ice-sheet modeling tightly constrained by empirical studies provides an effective framework to reconstruct past climatic and environmental conditions. Scotland was severely affected by the abrupt climate change associated with the Younger Dryas Stade, during which an extensive ice sheet formed across the west highlands after a period of ice-free conditions. Here, a quasi-three-dimensional, time-dependent ice flow/mass-balance model is developed and applied to Scotland at 1 km resolution. The flow model is based on the driving stress approximation with an additional longitudinal correction term, essential at this scale of operation. Surface mass balance is driven by temperature and precipitation changes and further mass wastage is achieved through an empirically defined calving term. The ice dynamics and mass-balance components are coupled through the equation for mass continuity, which is integrated through time over a finite-difference grid which yields the geometric evolution of the ice sheet. Initial experiments reveal the model to be relatively insensitive to internal parameters but highly sensitive to mass balance. Furthermore, these experiments indicate that Scotland is readily susceptible to glaciation with large glaciers building up on the flanks of Ben Nevis after a temperature depression of 2.5°C, under present-day precipitation. The Younger Dryas is modeled using a GRIP temperature series locally adjusted for amplitude and a systematic series of runs enables the isolation of the climate which best matches mapped ice limits. This “optimum-fit” configuration requires an annual temperature cooling of 8°C and the introduction of substantial west–east and south–north precipitation gradients of 40 and 50%, respectively, to the present-day regime. Under these conditions, a series of substantial independent regional ice centers develop in agreement with trimline studies and after 550 year the modeled ice sheet closely resembles the maximum limits as indicated by field mapping. However, modeled ice continues ...