Greenland surface air temperature changes from 1981 to 2019 and implications for ice‐sheet melt and mass‐balance change

Abstract

We provide an updated analysis of instrumental Greenland monthly temperature data to 2019, focusing mainly on coastal stations but also analysing icesheet records from Swiss Camp and Summit. Significant summer (winter) coastal warming of $1.7 (4.4) C occurred from 1991-2019, but since 2001 overall temperature trends are generally flat and insignificant due to a cooling pattern over the last 6-7 years. Inland and coastal stations show broadly similar temperature trends for summer. Greenland temperature changes are more strongly correlated with Greenland Blocking than with North Atlantic Oscillation changes. In quantifying the association between Greenland coastal temperatures and Greenland Ice Sheet (GrIS) mass-balance changes, we show a stronger link of temperatures with total mass balance rather than surface mass balance. Based on Greenland coastal temperatures and modelled mass balance for the 1972-2018 period, each 1 C of summer warming corresponds to $(91) 116 GtÁyr −1 of GrIS (surface) mass loss and a 26 GtÁyr −1 increase in solid ice discharge. Given an estimated 4.0-6.6 C of further Greenland summer warming according to the regional model MAR projections run under CMIP6

Brief communication: CMIP6 does not suggest any atmospheric blocking increase in summer over Greenland by 2100

“…Greenland blocking events are evaluated using the 500 hPa geopotential height (Z500) averaged and areaweighted over the region 60-80 N, 20-80 W, defined as the Greenland Blocking Index (GBI, Fang, 2004;Hanna et al, 2013Hanna et al, , 2014Hanna et al, , 2015Hanna et al, , 2016Hanna et al, , 2018aHanna et al, , 2020 which is used here to assess the representation in CMIP5 and CMIP6 models of the recent summer blocking events observed over Greenland. The GBI and thus summer Z500 increase reported over these last few decades, is variously and indeterminately influenced by two factors: (1) global climate warming and, (2) atmospheric dynamical changes linked to a more meridional configuration of the polar jet stream that favours anticyclonic conditions over Greenland (Overland et al, 2012).…”

The role of blocking circulation and emerging open water feedbacks on Greenland cold‐season air temperature variability over the last century

“…Coastal Greenland air temperature analyses have largely centred on either identifying trends, often with emphasis on the summer melt season, or placing the recent multidecadal warming pattern in historical context, such as against the early 20th century warm period (Hanna et al ., 2012; Mernild et al ., 2014; Abermann et al ., 2017; Hanna et al ., 2020b). Much less attention has been paid to Greenland's autumn and winter temperature variability and identifying linkages and driving factors between the multidecadal temperature patterns and contemporaneous and lagged North Atlantic boundary (i.e., sea ice and SST) and atmospheric conditions.…”

Sources of Uncertainty in Greenland Surface Mass Balance in the 21<sup>st</sup> century

“…They used the high-end scenario in CMIP5 with a representative concentration pathway (RCP) that leads to a radiative forcing of 8.5 Wm 2 at the end of the 21st century (RCP8.5), comparable to the SSP585 pathway we used here. Detailed SMB estimates are also available from the regional climate model MAR forced by a selection of CMIP6 global climate models (Hanna et al, 2020). This study also finds the familiar acceleration in mass loss.…”

“…However, these models are computationally expensive, leaving their use to evaluating only a few climate models (Fettweis et al, 2008;Franco et al, 2011;Fettweis et al, 2013;Hanna et al, 2020). In Fettweis et al (2008), a multiple regression for the SMB changes as a function of temperature and precipitation is performed to calculate the SMB changes also for the CMIP3 models that they have not simulated.…”

“…In Fettweis et al (2008), a multiple regression for the SMB changes as a function of temperature and precipitation is performed to calculate the SMB changes also for the CMIP3 models that they have not simulated. For CMIP6, Hanna et al (2020) simulated the SMB of Greenland using the output of five climate models. Hofer et al (2020) showed that the predicted climate from these representatively selected climate models leads to a larger GrIS SMB decrease in CMIP6 than in CMIP5.…”