Projected changes in solar UV radiation in the Arctic and sub-Arctic Oceans: Effects from changes in reflectivity, ice transmittance, clouds, and ozone

Abstract

Ultraviolet-B (UV-B), UV-A, and erythemal solar irradiance over ocean-covered areas north of 55°N are simulated for the past (1950-1960), present (2005-2015), and future (2090-2100) using a radiative transfer model. The simulations focus mainly on the effects of changes in ocean surface reflectivity, cloudiness, and stratospheric ozone. Based on projected changes in sea ice cover and thickness, changes in irradiance transmitted into the ocean are also derived. The input parameters of the radiative transfer model were obtained from four Coupled Model Intercomparison Project phase 5 Earth System Models driven by the emission scenarios Representative Concentration Pathway (RCP) 4.5 and RCP 8.5. Over a large fraction of the area under study, the overall effect from the projected changes in the factors considered is a reduction in the ultraviolet solar irradiance by the end of the 21st century relative to the levels in the 1950s. Increases were projected only for all skies during August for locations below 65°N due to the projected decrease in cloudiness. The reduction in clear-sky UV-A irradiance (on average 4-7% depending on scenario and season) is entirely driven by the reduction in surface reflectivity, while the projected ozone recovery is responsible for a great portion of the reduction in clear-sky UV-B irradiance (10-18% on average). Under all skies, the changes in the monthly mean noontime erythemal irradiance range from +15% to À38%, depending on the location and season. Compared to the 1950s, up to 10 times higher levels of UV-B irradiance are projected to enter large parts of the Arctic Ocean by 2100, mainly because of the partial disappearance of sea ice.

The interactive effects of stratospheric ozone depletion, UV radiation, and climate change on aquatic ecosystems

“…Models predict that the decline in ice cover will cause as much as a 10-fold increase in UV-B radiation entering Arctic surface waters. 78 Simultaneously, photosynthetically active radiation (PAR, 400-700 nm) will increase, promoting increased production. Without ice, the water is also affected by wind, which enhances mixing.…”

Windows in Arctic sea ice: Light transmission and ice algae in a refrozen lead

“…The new ice‐free areas have prompted an increase in phytoplankton primary production [ Arrigo and van Dijken , ]. In ice‐covered areas, thinning of the ice results in increased light availability in the visible range [ Nicolaus et al ., ] and exposure to ultraviolet light [ Fountoulakis et al ., ] for algae both associated with the ice (ice algae) and in the underlying water column (phytoplankton).…”

Concentrations of sunscreens and antioxidant pigments in Arctic Calanus spp. in relation to ice cover, ultraviolet radiation, and the phytoplankton spring bloom

“…But at the same time other studies indicate that there will be nearly ice‐free Arctic summers within the first half of the 21 st century (IPCC ; Overland and Wang ). Hence, previously ice‐covered areas will be exposed to up to 10 times stronger UVB‐radiation by 2100 compared with 1950 levels and an earlier onset of ice‐breakup will furthermore prolong yearly UVR exposure in aquatic systems (Perovich ; Perovich ; Fountoulakis et al ; Bais et al ). Ice cover in Disko Bay has decreased by approximately 50% during the last couple of decades (Hansen et al ), suggesting an overall increased UV‐threat.…”

“…Despite the fact that global levels of ozone-destructive pollutants are decreasing, large ozone reductions are still observed in both hemispheres, especially in Antarctic and Arctic systems (Tedetti and Sempere 2006;Andrady et al 2015). Ice cover reduces UVR exposure of ocean surfaces; however, the ongoing reduction of the Arctic Sea ice coverage has been estimated to increase the exposure of surface waters in the Arctic with up to 10 times higher levels of UVB irradiance by 2100 compared with 1950 levels (IPCC 2013;Fountoulakis et al 2014;Bais et al 2015).…”