Greenland Blocking Index 1851–2015: a regional climate change signal

Hanna, Edward; Cropper, Thomas; Rj, Hall; Cappelen, John

doi:10.1002/joc.4673

Cited by 211 publications

(308 citation statements)

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“…for large-scale atmospheric drivers Hanna et al, 2013aHanna et al, , 2014Hanna et al, , 2016McLeod and Mote, 2016) and local feedback processes. Especially important is the albedo-melt feedback , which constitutes the darkening of snow once it has melted, as well as the lengthening of the exposure of dark, bare ice in the ablation zone once the winter snow has melted away (Tedesco et al, 2011).…”

Section: Smbmentioning

confidence: 99%

On the recent contribution of the Greenland ice sheet to sea level change

et al. 2016

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Abstract. We assess the recent contribution of the Greenland ice sheet (GrIS) to sea level change. We use the mass budget method, which quantifies ice sheet mass balance (MB) as the difference between surface mass balance (SMB) and solid ice discharge across the grounding line (D). A comparison with independent gravity change observations from GRACE shows good agreement for the overlapping period 2002-2015, giving confidence in the partitioning of recent GrIS mass changes. The estimated 1995 value of D and the 1958-1995 average value of SMB are similar at 411 and 418 Gt yr −1 , respectively, suggesting that ice flow in the mid1990s was well adjusted to the average annual mass input, reminiscent of an ice sheet in approximate balance. Starting in the early to mid-1990s, SMB decreased while D increased, leading to quasi-persistent negative MB. About 60 % of the associated mass loss since 1991 is caused by changes in SMB and the remainder by D. The decrease in SMB is fully driven by an increase in surface melt and subsequent meltwater runoff, which is slightly compensated by a small (< 3 %) increase in snowfall. The excess runoff originates from lowlying (< 2000 m a.s.l.) parts of the ice sheet; higher up, increased refreezing prevents runoff of meltwater from occurring, at the expense of increased firn temperatures and depleted pore space. With a 1991-2015 average annual mass loss of ∼ 0.47 ± 0.23 mm sea level equivalent (SLE) and a peak contribution of 1.2 mm SLE in 2012, the GrIS has recently become a major source of global mean sea level rise.

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Section: Smbmentioning

confidence: 99%

On the recent contribution of the Greenland ice sheet to sea level change

et al. 2016

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“…The volume of meltwater generated at the GrIS surface has increased dramatically in recent years due to an expansion of ice sheet melt extent [12] and enhanced local melt rates [13] the result of: warmer air temperatures [14]; decreasing albedo [15] due to a darkening ice surface caused by increased aeolian dust [16], exposure of dirty Holocene ice [17], increased biota and cryoconite [18] and changing snowpack structure and moisture content [19]; decreased meltwater retention capacity in the firn [20]; and changing radiation budgets associated with synoptically driven changes in cloud cover [21,22]. The impact of this enhanced melt is reflected in the GrIS's increasingly negative balance, contributing 0.5 mm year to sea level between 1991 and 2015, at an accelerating rate of loss of~17 Gt year −2 [23•].…”

Section: Supraglacial Meltwater Processesmentioning

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

100

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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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“…Silmann et al 2011). Recent studies identified significant decadal to multidecadal variations in the blocking frequency over Greenland (McLeod and Mote 2016;Hanna et al 2016) and the whole North Atlantic region (e.g. Häkkinen et al 2011, Ionita et al, 2016.…”

Section: Introductionmentioning

confidence: 99%