The darkening of the Greenland ice sheet: trends,  drivers, and projections (1981–2100)

Tedesco, Marco; Doherty, S. J.; Fettweis, Xavier; Alexander, Patrick; Jeyaratnam, Jeyavinoth; Stroeve, Julienne

doi:10.5194/tc-10-477-2016

Cited by 177 publications

(157 citation statements)

References 68 publications

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“…There is a pressing need to determine how the recent darkening of the ice sheet surface will evolve and thus how the associated changing albedo will impact surface mass balance [19,121]. This understanding is critical in order to improve model projections of future runoff from the ice sheet, which is the process that already dominates the GrIS's negative mass balance trend.…”

Section: Darkening Of the Ice Sheetmentioning

confidence: 99%

Recent Advances in Our Understanding of the Role of Meltwater in the Greenland Ice Sheet System

Nienow

Sole

Slater

et al. 2017

Curr Clim Change Rep

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Purpose of the Review This review discusses the role that meltwater plays within the Greenland ice sheet system. The ice sheet's hydrology is important because it affects mass balance through its impact on meltwater runoff processes and ice dynamics. The review considers recent advances in our understanding of the storage and routing of water through the supraglacial, englacial, and subglacial components of the system and their implications for the ice sheet. Recent Findings There have been dramatic increases in surface meltwater generation and runoff since the early 1990s, both due to increased air temperatures and decreasing surface albedo. Processes in the subglacial drainage system have similarities to valley glaciers and in a warming climate, the efficiency of meltwater routing to the ice sheet margin is likely to increase. The behaviour of the subglacial drainage system appears to limit the impact of increased surface melt on annual rates of ice motion, in sections of the ice sheet that terminate on land, while the large volumes of meltwater routed subglacially deliver significant volumes of sediment and nutrients to downstream ecosystems. Summary Considerable advances have been made recently in our understanding of Greenland ice sheet hydrology and its wider influences. Nevertheless, critical gaps persist both in our understanding of hydrology-dynamics coupling, notably at tidewater glaciers, and in runoff processes which ensure that projecting Greenland's future mass balance remains challenging.

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Section: Darkening Of the Ice Sheetmentioning

confidence: 99%

Recent Advances in Our Understanding of the Role of Meltwater in the Greenland Ice Sheet System

Nienow

Sole

Slater

et al. 2017

Curr Clim Change Rep

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“…Algal blooms over Greenland have been shown to substantially reduce surface albedo (Lutz et al, 2016;Musilova et al, 2016;Stibal et al, 2017). Simulations show that changes in albedo due to LAI might significantly affect the surface mass balance of ice sheets during glacial times Krinner et al, 2006), at present (Dumont et al, 2014;Tedesco et al, 2016) and in future climate change scenarios (Goelles et al, 2015). In this study we explore the sensitivity of ice sheet and climate evolution over the last glacial cycle to the representation of snow albedo in the CLIMBER-2 Earth system model of intermediate complexity.…”

Section: Introductionmentioning

confidence: 99%

The importance of snow albedo for ice sheet evolution over the last glacial cycle

Willeit

Ganopolski

2018

Clim. Past

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Abstract. The surface energy and mass balance of ice sheets strongly depends on the amount of solar radiation absorbed at the surface, which is mainly controlled by the albedo of snow and ice. Here, using an Earth system model of intermediate complexity, we explore the role played by surface albedo for the simulation of glacial cycles. We show that the evolution of the Northern Hemisphere ice sheets over the last glacial cycle is very sensitive to the representation of snow albedo in the model. It is well known that the albedo of snow depends strongly on snow grain size and the content of lightabsorbing impurities. Excluding either the snow aging effect or the dust darkening effect on snow albedo leads to an excessive ice build-up during glacial times and consequently to a failure in simulating deglaciation. While the effect of snow grain growth on snow albedo is well constrained, the albedo reduction due to the presence of dust in snow is much more uncertain because the light-absorbing properties of dust vary widely as a function of dust mineral composition. We also show that assuming slightly different optical properties of dust leads to very different ice sheet and climate evolutions in the model. Conversely, ice sheet evolution is less sensitive to the choice of ice albedo in the model. We conclude that a proper representation of snow albedo is a fundamental prerequisite for a successful simulation of glacial cycles.

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“…Moderate Resolution Imaging Spectroradiometer (MODIS) observations are among the best tools available to evaluate these albedo feedbacks. Several studies have used MODIS data to study the magnitude of ongoing albedo trends and assess their role in enhancing the impact of climate warming on the ice sheet (e.g., Tedesco et al, 2011Tedesco et al, , 2016Box et al, 2012;Stroeve et al, 2013). A challenge in using long-term satellite records to detect change is maintaining consistent instrument performance.…”

Section: Introductionmentioning

confidence: 99%

Impact of MODIS sensor calibration updates on Greenland Ice Sheet surface reflectance and albedo trends

2017

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Abstract. We evaluate Greenland Ice Sheet (GrIS) surface reflectance and albedo trends using the newly released Collection 6 (C6) MODIS (Moderate Resolution Imaging Spectroradiometer) products over the period [2001][2002][2003][2004][2005][2006][2007][2008][2009][2010][2011][2012][2013][2014][2015][2016]. We find that the correction of MODIS sensor degradation provided in the new C6 data products reduces the magnitude of the surface reflectance and albedo decline trends obtained from previous MODIS data (i.e., Collection 5, C5). Collection 5 and 6 data product analysis over GrIS is characterized by surface (i.e., wet vs. dry) and elevation (i.e., 500-2000 m, 2000 m and greater) conditions over the summer season from 1 June to 31 August. Notably, the visible-wavelength declining reflectance trends identified in several bands of MODIS C5 data from previous studies are only slightly detected at reduced magnitude in the C6 versions over the dry snow area. Declining albedo in the wet snow and ice area remains over the MODIS record in the C6 product, albeit at a lower magnitude than obtained using C5 data. Further analyses of C6 spectral reflectance trends show both reflectance increases and decreases in select bands and regions, suggesting that several competing processes are contributing to Greenland Ice Sheet albedo change. Investigators using MODIS data for other ocean, atmosphere and/or land analyses are urged to consider similar re-examinations of trends previously established using C5 data.

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The darkening of the Greenland ice sheet: trends, drivers, and projections (1981–2100)

Cited by 177 publications

References 68 publications

Recent Advances in Our Understanding of the Role of Meltwater in the Greenland Ice Sheet System

Recent Advances in Our Understanding of the Role of Meltwater in the Greenland Ice Sheet System

The importance of snow albedo for ice sheet evolution over the last glacial cycle

Impact of MODIS sensor calibration updates on Greenland Ice Sheet surface reflectance and albedo trends

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