The Critical Role of Euro‐Atlantic Blocking in Promoting Snowfall in Central Greenland

Abstract

The Greenland Ice Sheet (GrIS) is losing mass at an increasing rate yet mass gain from snowfall still exceeds the loss attributed to surface melt processes on an annual basis. This work assesses the relationship between persistent atmospheric blocking across the Euro‐Atlantic region and enhanced precipitation processes over the central GrIS during June–August and September–November. Results show that the vast majority of snowfall events in the central GrIS coincide with Euro‐Atlantic blocking. During June–August, snowfall events are produced primarily by mixed‐phase clouds (88%) and are linked to a persistent blocking anticyclone over southern Greenland (84%). The blocking anticyclone slowly advects warm, moist air masses into western and southern Greenland, with positive temperature and water vapor anomalies that intensify over the central GrIS. A zonal integrated water vapor transport pattern south of Greenland indicates a southern shift of the North Atlantic storm track associated with the high‐latitude blocking. In contrast, snowfall events during September–November are largely produced by ice‐phase clouds (85%) and are associated with a blocking anticyclone over the Nordic Seas and blocked flow over northern Europe (78%). The blocking anticyclone deflects the westerly North Atlantic storm track poleward and enables the rapid transport of warm, moist air masses up the steep southeastern edge of the GrIS, with positive temperature and water vapor anomalies to the east and southeast of Greenland. These results emphasize the critical role of Euro‐Atlantic blocking in promoting snowfall processes over the central GrIS and the importance of accurate representation of blocking in climate model projections.

Marine Cold‐Air Outbreak Snowfall in the North Atlantic: A CloudSat Perspective

“…Persistent anticyclonic blocking over the Greenland Ice Sheet (e.g., Hanna et al., 2016) and in the North Atlantic (e.g., Papritz & Grams, 2018) may promote MCAO formation east of Greenland as air masses on the eastern flank originate from cold continental or sea ice locations and advect over the open ocean. West of Greenland, this circulation advects warm, moist air onto the Greenland Ice Sheet and is responsible for the majority of enhanced SON snowfall events over central Greenland (Pettersen et al., 2022). This warm air would be categorized as non‐CAO over the Baffin Bay if $$\theta $$ SST $${\le} $$ $$\theta $$ 850 , which may explain enhanced SON 2CSNOW rates west of Greenland during non‐CAO conditions (Figure 3f).…”

“…North Atlantic MCAOs are often found in the cold sector of cyclones (e.g., Afargan‐Gerstman et al., 2020; Fletcher et al., 2016a; Kolstad et al., 2009; Papritz & Grams, 2018) and in association with polar lows which can cause severe weather (e.g., Abel et al., 2017; Kolstad et al., 2009; Landgren et al., 2019; Shapiro et al., 1987; Terpstra et al., 2021). On longer timescales, persistent anticyclonic blocking in the North Atlantic, that is found to inundate the Greenland Ice Sheet with precipitation (Papritz & Grams, 2018; Pettersen et al., 2022), simultaneously forces cold air equatorward on its eastward flank, initiating MCAOs impacting Europe (e.g., Papritz & Grams, 2018; Smith & Sheridan, 2021; Terpstra et al., 2021).…”

CloudSat Observations Show Enhanced Moisture Transport Events Increase Snowfall Rate and Frequency Over Antarctic Ice Sheet Basins

“…Additionally, Milani et al (2018) evaluated the CloudSat 2C-SNOW-PROFILE snowfall rate intensity and frequency and found agreement between the retrievals and reanalysis products over the interior of the AIS. Previous work has also linked moisture convergence and resulting enhanced IVT to increased snowfall rates over the Greenland and Antarctic ice sheets using ground-based observations and reanalysis (e.g., Gorodetskaya et al, 2014;Maclennan & Lenaerts, 2021;Maclennan et al, 2022Maclennan et al, , 2023Pettersen et al, 2022). However, no studies to date have examined satellite observations of snowfall characteristics over regions of the AIS concurrently with periods of enhanced IVT.…”

Observations of Fog‐Aerosol Interactions Over Central Greenland

“…Central Greenland is a unique environment in the Northern Hemisphere: A uniform surface of snow‐covered ice extends for over 250 km in every direction from the ice sheet's highest point at 3250 m a.s.l (Howat et al., 2017). The structure of the atmospheric boundary layer over the ice sheet is driven by large‐scale circulation, including atmospheric rivers associated with extratropical storms (Gallagher et al., 2018; Mattingly et al., 2018) and blocking anticyclones (Pettersen et al., 2022), and is modulated locally by strong radiative cooling at the ice sheet surface (Hoch et al., 2007). Under quiescent conditions (clear skies, light winds), surface radiative cooling frequently drives the formation of supercooled radiation fog through the condensation of water onto aerosol particles that act as cloud condensation nuclei (CCN) (Bergin et al., 1994; Cox et al., 2019).…”

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The structure of the atmospheric boundary layer over the ice sheet is driven by large-scale circulation, including atmospheric rivers associated with extratropical storms (Gallagher et al, 2018;Mattingly et al, 2018) and blocking anticyclones (Pettersen et al, 2022), and is modulated locally by strong radiative cooling at the ice sheet surface (Hoch et al, 2007). Under quiescent conditions (clear skies, light winds), surface radiative cooling frequently drives the formation of supercooled radiation fog through the condensation of water onto aerosol particles that act as cloud condensation nuclei (CCN) (Bergin et al, 1994;Cox et al, 2019).At Summit Station (Summit), a research base located near the highest point on the Greenland Ice Sheet (72.57°N, −38.47°E), fogs comprised of supercooled droplets occur year-round even when the surface temperature falls below −30°C (Cox et al, 2019).

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