Local-scale deposition of surface snow on the Greenland ice sheet

Abstract

Abstract. Ice cores from polar ice sheets and glaciers are an important climate archive. Snow layers, consecutively deposited and buried, contain climatic information from the time of their formation. However, particularly low-accumulation areas are characterised by temporally intermittent precipitation, which can be further redistributed after initial deposition, depending on the local surface features at different spatial scales. Therefore, the accumulation conditions at an ice core site influence the quantity and quality of the recorded climate signal in proxy records. This study aims to characterise the local accumulation patterns and the evolution of the snow height to describe the contribution of the snow (re-)deposition to the overall noise level in climate records from ice cores. To this end, we applied a structure-from-motion photogrammetry approach to generate near-daily elevation models of the surface snow for a 195 m2 area in the vicinity of the deep drilling site of the East Greenland Ice-core Project in northeast Greenland. Based on the snow height information we derive snow height changes on a day-to-day basis throughout our observation period from May to August 2018 and find an average snow height increase of ∼ 11 cm. The spatial and temporal data set also allows an investigation of snow deposition versus depositional modifications. We observe irregular snow deposition and erosion causing uneven snow accumulation patterns, a removal of more than 60 % of the deposited snow, and a negative relationship between the initial snow height and the amount of accumulated snow. Furthermore, the surface roughness decreased by approximately a factor of 2 throughout the spring and summer season at our study site. Finally, our study shows that structure from motion is a relatively simple method to demonstrate the potential influences of depositional processes on proxy signals in snow and ice.

Exploring the role of snow metamorphism on the isotopic composition of the surface snow at EastGRIP

“…Temperatures below -25 • C are characterised by the same slope defined by the model (-0.54 m 2 kg −1 day −1 ), but with a significantly higher intercept of 29 m s −1 day −1 compared to 14.7 m s −1 day −1 for temperatures above -25 The characterization of the SSA decays provide a basis to explore how snow metamorphism of surface snow plays a role for the alteration of isotopic composition of Greenland snow after deposition. A recent study at EastGRIP has shown the significant in-homogeneity in surface snow due to post-depositional reworking of the snow (Zuhr et al, 2021). The focus for this manuscript is to identify signal coherence between physical properties and isotopic composition of surface snow subject to during 2018 and 2019 seasons, while the signal is less clear during 2017 (Fig.…”

Atmosphere‐Snow Exchange Explains Surface Snow Isotope Variability

“…For evaluating the importance of sublimation for the summer signal in the snowpack isotope record the comparison of the precipitation versus the sublimation signal both in terms of mass balance and preserved signal seems necessary. However, with no information about the precipitation's isotopic composition and mass (Zuhr et al., 2021 ), this comparison is infeasible. Instead, we calculate the observed change in snow isotopic composition during the observation periods and exclude days with snowfall or wind redistribution.…”

“…Besides uneven deposition through precipitation intermittency (Casado et al., 2020 ; Münch et al., 2021 ; Persson et al., 2011 ) and precipitation seasonality (Cuffey & Steig, 1998 ; Zheng et al., 2018 ), wind redistribution (Zuhr et al., 2021 ) and mixing with drifting snow (Stenni et al., 2016 ), post‐depositional processes are suggested to alter the isotopic composition of the snow. Specifically, vapor‐snow exchange processes occur continuously at the surface through turbulent humidity fluxes (Wahl et al., 2021 ) which are defined by local climate and below the surface during snow metamorphism.…”

From ice core to ground-penetrating radar: representativeness of SMB at three ice rises along the Princess Ragnhild Coast, East Antarctica

“…The ice core SMB record can also be strongly modified by post-depositional reworking of the surface by winds that can erode away snow in one location and redeposit it several kilometers away or remove it completely through wind-driven sublimation (King and others, 2004; Lenaerts and others, 2019; Agosta and others, 2019). SMB can be highly variable, even over the distance of a few meters (Gautier and others, 2016; Kausch and others, 2020; Münch and others, 2021), and post-depositional reworking can further modify this spatial SMB variability (Zuhr and others, 2021). With a surface area of cm, ice cores therefore have the potential to capture a local and noisy record of past SMB conditions.…”