Abstract
The dramatic warming of the Arctic over the last three decades has reduced both the thickness and extent of sea ice, opening opportunities for business in diverse sectors and increasing human exposure to meteorological hazards in the Arctic. It has been suggested that these changes in environmental conditions have led to an increase in extreme cyclones in the region, therefore increasing this hazard. In this study, we investigate the response of Arctic synoptic scale cyclones to climate change in a large initial value ensemble of future climate projections with the CESM1-CAM5 climate model (CESM-LE). We find that the response of Arctic cyclones in these simulations varies with season, with significant reductions in cyclone dynamic intensity across the Arctic basin in winter, but with contrasting increases in summer intensity within the region known as the Arctic Ocean cyclone maximum. There is also a significant reduction in winter cyclogenesis events within the Greenland–Iceland–Norwegian sea region. We conclude that these differences in the response of cyclone intensity and cyclogenesis, with season, appear to be closely linked to changes in surface temperature gradients in the high latitudes, with Arctic poleward temperature gradients increasing in summer, but decreasing in winter.
Highlights
Unprecedented warming in the Arctic has led to a dramatic reduction in both the extent and thickness of Arctic sea ice (Stroeve et al 2011), opening up opportunities for business in diverse sectors such as fossil fuel and mineral extraction, shipping and tourism (Jung et al 2016)
There is a concurrent increase in track density on the equatorward flank of the North Atlantic storm track, suggesting that these changes in the Arctic are the result of the tilt of the North Atlantic storm track becoming more zonal, which has been seen in future projections with other CMIP5 models (Zappa et al 2013a)
In this study we find that the projected response of the Arctic cyclone climatology in CESM1 is seasonally dependent: storm dynamic intensity is significantly reduced in winter months but in summer large areas of the Arctic dynamic intensity is projected to increase
Summary
Unprecedented warming in the Arctic has led to a dramatic reduction in both the extent and thickness of Arctic sea ice (Stroeve et al 2011), opening up opportunities for business in diverse sectors such as fossil fuel and mineral extraction, shipping and tourism (Jung et al 2016). Using a vorticity feature tracking algorithm, Orsolini and Sorteberg (2009) found that Arctic summer (JJA) cyclone frequency and dynamic intensity, measured by relative vorticity, significantly increased in the Bergen climate model under two emissions scenarios This occurs against a backdrop of reduced northern hemisphere storminess. This approach of using a large initial-value ensemble has two advantages over previous modelling studies in this area: firstly, the large number of ensemble members enables the forced response to climate change to be well characterised in the model It enables the role of internal variability, which is thought to significantly affect trends in Arctic cyclones (Zhang et al 2004), and those at lower latitudes (Villarini and Vecchi 2012), to be quantified. We will focus on DJF and JJA because these seasons experience the largest contrast in terms of the seasonal response to climate change
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