Recent North Greenland temperature warming and accumulation

Abstract

Abstract. In a warming climate concise knowledge of the mass balance of the Greenland ice sheet is of utter importance. Speculations that current warming will increase the snow accumulation and mitigate mass balance losses are unconstrained as accumulation data across large regions of the northern ice sheet are scarce. We reconstructed the accumulation from six north Greenland shallow firn cores (~10 m) and eight snow cores (~2 m) to constrain recent accumulation patterns in northern Greenland and calculated recent warming in the same area using borehole temperature measurements. We find an increase in temperatures in the north Greenland interior of 0.9 to 2.5 °C (method and site dependent) per decade over the past two decades in line with an Arctic amplified anthropogenic warming. We compare annual reconstructed accumulation from the firn cores (1966–2015) to radar estimates and to annual re-analysis data (1980–2016) of precipitation subtracted evaporation from the regional climate model HIRHAM5, operated by the Danish Meteorological Institute. The spatial variability resembles that observed in earlier estimates with a clear increase west of the topographic divide and a low accumulation area across the north-eastern ice sheet. Our accumulation results are comparable to earlier firn core estimates, despite being larger in the east. We only find a positive significant trend in the accumulation for the period 2000–2010 to the northwest. In the vicinity of the EGRIP deep ice core drilling site, we find variable accumulation patterns for two 15 km apart firn cores likely owing to local topographic effects as a result of the North East Greenland Ice Stream dynamics.

A portable Lightweight In Situ Analysis (LISA) box for ice and snow analysis

“…We note that our reconstructed accumulation at NEEM rely on just one year (summer 2018-summer 2019), which is known to be a year of low accumulation in Northern Greenland, while earlier estimates rely on several hundreds of years (Masson-Delmotte et al, 2015;Rasmussen et al, 2013). For the site B16 and the sites closer to EastGRIP (S5 and S7) our results from 2019 (~14.9-17.6 cm w.eq annually) are considerably higher than the 11.2 cm w.eq previously observed in the 400 yr NEGIS ice core obtained at the EastGRIP site in 2012 (Vallelonga et al, 2014), and also larger than the more recent estimates from radar (13 cm w. eq, (Karlsson et al, 2020)), firn cores (13.7 and 14.6 (Kjaer et al, 2021)), snow pits (14.6 cm w. eq. (Nakazawa et al, 2020)) and the 14.1 cm w.eq observed at B16 site (Weissbach et al, 2016).…”

“…We also highlightthat variability between individual years for eg. B22 and S4 is larger than the difference to previous estimates from the area, and that at the sites where more snow cores were obtained (EastGRIP-2017, NEEM, S5 and B19) the difference in accumulation between individual years is up to 20% ( Figure S4, Supplementary information) further other studies have shown a similar variability investigating shorter firn cores (NEEM-25%, EastGRIP -30% (Kjaer et al, 2021)). This illustrates the need to do several measurements over time at each site if aiming to reconstruct the climatic mean accumulation or to use firn cores to do so.…”

Comment on tc-2021-51

“…We note that our reconstructed accumulation at NEEM rely on just one year (summer 2018-summer 2019), which is known to be a year of low accumulation in Northern Greenland, while earlier estimates rely on several hundreds of years (Masson-Delmotte et al, 2015;Rasmussen et al, 2013). For the site B16 and the sites closer to EastGRIP (S5 and S7) our results from 2019 (~14.9-17.6 cm w.eq annually) are considerably higher than the 11.2 cm w.eq previously observed in the 400 yr NEGIS ice core obtained at the EastGRIP site in 2012 (Vallelonga et al, 2014), and also larger than the more recent estimates from radar (13 cm w. eq, (Karlsson et al, 2020)), firn cores (13.7 and 14.6 (Kjaer et al, 2021)), snow pits (14.6 cm w. eq. (Nakazawa et al, 2020)) and the 14.1 cm w.eq observed at B16 site (Weissbach et al, 2016).…”

NEEM to EastGRIP Traverse – spatial variability, seasonality, extreme events and trends in common ice core proxies over the past decades

“…The traverse went from the NEEM deep ice core drill site (77N25.219',51W09.588') to the EastGRIP deep ice core drill site (75N37.501',35W58.809'). Cores were drilled from the surface to a depth between 9.08 m and 14.01 m. The position and time period covered by the firn cores labelled T2015-A1 to T2015-A6 can be found in Table 1 and Figure 1 (Kjaer et al, 2021b).…”

“…In Copenhagen they were stored at -20 ºC until further cutting into sections of 3.4 x 3.4 cm just prior to measurements by CFA (Bigler et al 2011). (Kjaer et al, 2021b)…”