Drivers and Environmental Responses to the Changing Annual Snow Cycle of Northern Alaska

Abstract

Linkages between atmospheric, ecological, and biogeochemical variables in the changing Arctic are analyzed using long-term measurements near Utqiaġvik (formerly Barrow), Alaska. Two key variables are the date when snow disappears in spring, as determined primarily by atmospheric dynamics, precipitation, air temperature, winter snow accumulation, and cloud cover, and the date of onset of snowpack in autumn that is additionally influenced by ocean temperature and sea ice extent. In 2015 and 2016 the snow melted early at Utqiaġvik owing mainly to anomalous warmth during May of both years attributed to atmospheric circulation patterns, with 2016 having the record earliest snowmelt. These years are discussed in the context of a 115-yr snowmelt record at Utqiaġvik with a trend toward earlier melting since the mid-1970s (–2.86 days decade–1, 1975–2016). At nearby Cooper Island, where a colony of seabirds, black guillemots, have been monitored since 1975, timing of egg laying is correlated with Utqiaġvik snowmelt with 2015 and 2016 being the earliest years in the 42-yr record. Ice out at a nearby freshwater lagoon is also correlated with Utqiaġvik snowmelt. The date when snow begins to accumulate in autumn at Utqiaġvik shows a trend toward later dates (+4.6 days decade–1, 1975–2016), with 2016 being the latest on record. The relationships between the lengthening snow-free season and regional phenology, soil temperatures, fluxes of gases from the tundra, and to regional sea ice conditions are discussed. Better understanding of these interactions is needed to predict the annual snow cycles in the region at seasonal to decadal scales and to anticipate coupled environmental responses.

Spring photosynthetic onset and net CO2 uptake in Alaska triggered by landscape thawing

“…We define seasonal‐onset dates for snow melt, thaw, GPP, and net C uptake for each grid point in the climatological mean. We acknowledge our short 3‐year period provides a small sample of northern high‐latitude springs but captures a range of variability including an average spring in 2012, cool and late spring in 2013, and warm and early spring in 2014 (Commane, Lindaas et al., ; Cox et al., ; Davidson et al., ; Euskirchen et al., ).…”

“…In particular, Luus et al. () show green‐up and budburst to occur 1–2 weeks prior to SIF‐based GPP onset in northern high latitude deciduous tundra ecosystems. Moreover, leaf‐level SIF measurements show close correspondence to photochemical reflectance index and chlorophyll carotenoid index optical indices during spring photosynthetic activation (from gas exchange measurements) in boreal evergreens, reflecting a reversal of nonphotochemical quenching and leaf pigments in spring with changes in chloroplast functioning during cold dehardening (Springer, Wang, & Gamon, ; Wong & Gamon, ).…”

Decadal changes of surface elevation over permafrost area estimated using reflected GPS signals

“…The thaw season lasts from early June to early August (Shiklomanov et al, 2010). According to the 1987-2016 climatological mean, the snowfree period typically lasts from July to mid-August (Cox et al, 2017). The active layer is dominantly organic-rich soil that is nearly saturated during the thaw seasons (Shiklomanov et al, 2010).…”

The Aleutian Low‐Beaufort Sea Anticyclone: A Climate Index Correlated With the Timing of Springtime Melt in the Pacific Arctic Cryosphere

“…Spring is a sensitive season for the Arctic terrestrial environment because snowmelt elicits responses in biogeochemical cycles, vegetation growth, ecology, soil temperature, and the surface energy budget (Cox et al, , and references therein). Recent years have seen winter and spring climate extremes in the Pacific Arctic, including the 2016 winter heat wave (Overland & Wang, ; Walsh et al, ), and springtime warmth in 2015 and 2016 leading to the fourth and first earliest dates of snowmelt, respectively, recorded at Utqiaġvik (formerly Barrow), Alaska (Cox et al, ). These events are consistent with anomalies in snow cover extent around the Pacific Arctic (Derksen et al, , ).…”

“…The latter has been linked to Arctic amplification in autumn and winter. Springtime warming has been less pronounced, however, and a trend toward earlier snowmelt dates at Utqiaġvik is likely influenced by variability in atmospheric circulation patterns (Cox et al, ; Stone et al, ). Indeed, a combination of factors contributed to the 2016 warmth, but circulation had greater importance at the end of the winter than at the beginning (Walsh et al, ).…”