Baffin Island snow extent sensitivity: Insights from a regional climate model

Abstract

[1] Recent modeling efforts suggest that the Little Ice Age (LIA) onset could be explained by a series of four large decadally-spaced volcanic eruptions. At that time, glaciers on Baffin Island advanced and did not retreat until the past century, perhaps due to Arctic and North Atlantic Ocean sea ice feedbacks. To try to determine what parameters sustain snow cover, we investigate the relative impacts of changes in radiation and advection on minimum summer snow extent over Baffin Island. We used the Weather Research and Forecasting (WRF) model to run eight 6 month long (April-September), 10 km resolution simulations, in which we varied boundary condition temperatures, solar radiation, and sea ice cover. Although the Control Run underestimated cloud cover and thus produced an exaggerated diurnal 2 m temperature cycle, the relative changes of snow extent show that WRF accurately simulates snow expansion into the same regions as during the LIA. With an average temperature decrease from current temperatures by À3.9 AE 1.1 K, it only requires one season for the model to lower the snowline by comparable elevation changes seen during the descent into the LIA. WRF's maximum snow line sensitivity is 7 K/km, within the range of the typically assumed lapse rate of 5-7 K/km in the Canadian Arctic. Thus, if a shift in the Arctic climate greatly expanded sea ice coverage following large volcanic eruptions, this would have been enough to perpetuate an ice sheet on Baffin Island throughout the LIA.Citation: Berdahl, M., and A. Robock (2013), Baffin Island snow extent sensitivity: Insights from a regional climate model,

The Latest on Volcanic Eruptions and Climate

“…[2012], who found changes in the North Atlantic Ocean circulation following volcanic eruptions that imply strengthened northward oceanic heat transport a decade after major eruptions, which contributes to persistent cooling over Arctic regions on decadal time scales. Berdahl and Robock [2013] supported this result, showing with a regional climate model that the Baffin ice sheet could persist even after volcanic forcing disappeared, given a cooler surrounding Arctic climate. Miller et al [2012] showed that while solar variations may also reinforce Little Ice Age climate variations, they were not necessary to initiate the Little Ice Age.…”

Eos, Transactions, American Geophysical Union Volume 94, Number 35, 27 August 2013

“…It also agrees with Zanchettin et al [2012], who found changes in the North Atlantic Ocean circulation following volcanic eruptions that imply strengthened northward oceanic heat transport a decade after major eruptions, which contributes to persistent cooling over Arctic regions on decadal time scales. Berdahl and Robock [2013] supported this result, showing with a regional climate model that the Baffin ice sheet could per sist even after volcanic forcing disappeared, given a cooler surrounding Arctic climate. Miller et al [2012] showed that while solar variations may also reinforce Little Ice Age climate variations, they were not necessary to initiate the Little Ice Age.…”

Northern Hemispheric cryosphere response to volcanic eruptions in the Paleoclimate Modeling Intercomparison Project 3 last millennium simulations

“…Models with higher peak elevations on Baffin Island tend to have colder mean summer climates. The two models with the coldest climate in the Baffin Island region, CCSM4, and GISS, also represent the high plateaus (400–700 m) [ Andrews et al ., ], elevations critical in fostering and sustaining large snow area change [ Berdahl and Robock , ].…”

“…Model resolution, and consequently topography, plays a strong role in determining mean climate over Baffin Island. Critical plateau elevations of 400–700 m, necessary for fostering and sustaining large snow area change [ Berdahl and Robock , ], are only represented in the CCSM4 and GISS models. In more than half of the models, warm summer climates over Baffin Island stunt snow expansion after volcanic eruptions completely.…”

“…Lowering the snowline into this region could cause a drastic increase in snow coverage. Berdahl and Robock [] found that in a 10 km resolution regional climate model, a summer temperature decrease of 3.9 ± 1.1 K from the current climate was necessary to lower the snowline by comparable elevation changes seen during the descent into the LIA on Baffin Island.…”