Northern Hemisphere storminess in the Norwegian Earth System Model (NorESM1-M)

Abstract

Abstract. Metrics of storm activity in Northern Hemisphere high and midlatitudes are evaluated from historical output and future projections by the Norwegian Earth System Model (NorESM1-M) coupled global climate model. The European Re-Analysis Interim (ERA-Interim) and the Community Climate System Model (CCSM4), a global climate model of the same vintage as NorESM1-M, provide benchmarks for comparison. The focus is on the autumn and early winter (September through December) -the period when the ongoing and projected Arctic sea ice retreat is the greatest. Storm tracks derived from a vorticity-based algorithm for storm identification are reproduced well by NorESM1-M, although the tracks are somewhat better resolved in the higherresolution ERA-Interim and CCSM4. The tracks show indications of shifting polewards in the future as climate changes under the Representative Concentration Pathway (RCP) forcing scenarios. Cyclones are projected to become generally more intense in the high latitudes, especially over the Alaskan region, although in some other areas the intensity is projected to decrease. While projected changes in track density are less coherent, there is a general tendency towards less frequent storms in midlatitudes and more frequent storms in high latitudes, especially the Baffin Bay/Davis Strait region in September. Autumn precipitation is projected to increase significantly across the entire high latitudes. Together with the projected loss of sea ice and increases in storm intensity and sea level, this increase in precipitation implies a greater vulnerability to coastal flooding and erosion, especially in the Alaskan region. The projected changes in storm intensity and precipitation (as well as sea ice and sea level pressure) scale generally linearly with the RCP value of the forcing and with time through the 21st century.

Wind Climatology for Alaska: Historical and Future

“…We therefore applied the same threshold criteria used for the eight coastal locations in Section 3.1 to the hourly wind output from the CM3and CCSM4-driven WRF model simulations. warming scenarios [22], and there is some evidence that storm tracks have already undergone such shifts in recent decades [23]. There is also the likelihood that increases in the fluxes of latent and sensible heat will increase storm intensity in areas of diminished sea ice, as will be (and already is) the case in the Bering and Chukchi Seas offshore of Nome and Barrow, respectively.…”

Climatological Characteristics of Historical and Future High-Wind Events in Alaska

“…The expectation of increased storm activity in the Arctic is supported by several recent modeling studies. [14] showed enhanced extratropical cyclone activity over the Eurasian Arctic in model projections for the end of the century, while [4] found indications of northward shifts of the major storm tracks during autumn in the late 21 st -century model projections. However, analyses of observational data have produced mixed results on trends of high-latitude storminess.…”

“…Moreover, evaluations of historical trends in sub-Arctic storminess and wind events have not provided compelling evidence of trends [3]. There are some indications from models of a northward shift of storm tracks over the North Atlantic Ocean [4] but the northern hemisphere observational data do not show a spatially coherent poleward shift in storm tracks [5].…”

Insight into real-world complexities is required to enable effective response from the aquaculture sector to climate change

“…It is expected that snowmelt floods will decrease in magnitude and frequency, but rainfall induced floods will increase [35]. Models suggest extreme precipitation events will increase in frequency and intensity [60] with severe consequences for western and southern Norway [61].…”