Ocean‐Induced Melt Triggers Glacier Retreat in Northwest Greenland

Wood, Michael; Rignot, Eric; Fenty, Ian; Menemenlis, Dimitris; Millan, Romain; Morlighem, Mathieu; Mouginot, J.; Seroussi, Hélène

doi:10.1029/2018gl078024

Cited by 81 publications

(104 citation statements)

References 41 publications

(68 reference statements)

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“…Over the past 2 decades, many glaciers along the northwest coast of Greenland have been retreating and accelerating, sometimes dramatically (e.g., Moon et al, 2012;Wood et al, 2018). It has been suggested that the retreat of these glaciers is initiated by the presence of warm and salty subsurface Atlantic Water (AW) in the fjords (e.g., Straneo et al, 2010;Straneo and Heimbach, 2013;Rignot et al, 2012;Holland et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Modeling the response of northwest Greenland to enhanced ocean thermal forcing and subglacial discharge

et al. 2019

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Abstract. Calving-front dynamics is an important control on Greenland's ice mass balance. Ice front retreat of marine-terminating glaciers may, for example, lead to a loss in resistive stress, which ultimately results in glacier acceleration and thinning. Over the past decade, it has been suggested that such retreats may be triggered by warm and salty Atlantic Water, which is typically found at a depth below 200–300 m. An increase in subglacial water discharge at glacier ice fronts due to enhanced surface runoff may also be responsible for an intensification of undercutting and calving. An increase in ocean thermal forcing or subglacial discharge therefore has the potential to destabilize marine-terminating glaciers along the coast of Greenland. It remains unclear which glaciers are currently stable but may retreat in the future and how far inland and how fast they will retreat. Here, we quantify the sensitivity and vulnerability of marine-terminating glaciers along the northwest coast of Greenland (from 72.5 to 76∘ N) to ocean forcing and subglacial discharge using the Ice Sheet System Model (ISSM). We rely on a parameterization of undercutting based on ocean thermal forcing and subglacial discharge and use ocean temperature and salinity from high-resolution ECCO2 (Estimating the Circulation and Climate of the Ocean, Phase II) simulations at the fjord mouth to constrain the ocean thermal forcing. The ice flow model includes a calving law based on a tensile von Mises criterion. We find that some glaciers, such as Dietrichson Gletscher or Alison Glacier, are sensitive to small increases in ocean thermal forcing, while others, such as Illullip Sermia or Cornell Gletscher, are remarkably stable, even in a +3 ∘C ocean warming scenario. Under the most intense experiment, we find that Hayes Gletscher retreats by more than 50 km inland by 2100 into a deep trough, and its velocity increases by a factor of 3 over only 23 years. The model confirms that ice–ocean interactions can trigger extensive and rapid glacier retreat, but the bed controls the rate and magnitude of the retreat. Under current oceanic and atmospheric conditions, we find that this sector of the Greenland ice sheet alone will contribute more than 1 cm to sea level rise and up to 3 cm by 2100 under the most extreme scenario.

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Section: Introductionmentioning

confidence: 99%

Modeling the response of northwest Greenland to enhanced ocean thermal forcing and subglacial discharge

et al. 2019

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“…to the mouths of fjords. Then, depending on the height of the fjord's sills, it can allow waters access to or block waters from reaching the marine terminating glaciers and accelerating their mass loss (Cai et al, 2017;Rignot et al, 2016b;Wood et al, 2018;Straneo et al, 2012). If the warm waters from the NASPG can reach these transverse troughs, changes in heat content of the NASPG may influence the state of marine terminating glaciers on the GrIS.…”

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Drivers for Atlantic-origin waters abutting Greenland

Gillard

Myers

2019

Preprint

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Abstract. The oceanic heat available in Greenland’s troughs is dependent on the location of the trough, the warm water origin, and how the water is impacted by local processes. This study investigates the mechanisms that bring warm water to the shelf and into the troughs abutting the Greenland Ice Sheet (GrIS). Warm water that is exchanged from the trough into the fjord may influence the melt on the marine terminating glaciers. Regional ocean model experiments showed that Melville Bay troughs experienced warming following 2009. An increase in ocean heat in these troughs may drive a retreat of the GrIS. In 2004 to 2006, model experiments captured an increase in onshore heat flux in the Disko Bay trough, coinciding with the timing of the disintegration of Jakobshavn Isbrae's floating tongue and observed ocean heat increase in Disko Bay. Warm Irminger water can extend far north into Baffin Bay, reaching as north as Melville Bay troughs. However, it diminishes north of 67° N on the east coast. Seasonality of the maximum onshore heat flux differs due to distance away from the original source. The north-west coast and south-east coast respond differently to changes in meltwater from Greenland and high frequency atmospheric phenomena. With a doubling of the GrIS meltwater, Baffin Bay troughs brought ∼40 % more heat. The lack of presence of storms resulted in an increase in heat flux (∼20 %) through Helheim glacier’s trough. These results demonstrate the importance of onshore heat transport through troughs and its potential implications to the GrIS.

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“…We attribute their presence to bedrock erosion from prior advances of glaciers in colder periods. Most of the channels are deep enough (>300 m) to enable the advection of warm, subsurface, salty AW to the glaciers, i.e., they are connected over distances long enough to transmit AW to the glacier fronts [29]. In the new map of part A, we detect prominent seafloor channels in front of Rink glacier (Figure 6b).…”

Section: Comparing the Bed Elevation Along A-a And B-b (mentioning

confidence: 90%

Bathymetry of Northwest Greenland Using “Ocean Melting Greenland” (OMG) High-Resolution Airborne Gravity and Other Data

Rignot

Millan

et al. 2019

Remote Sensing

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Marine-terminating glaciers dominate the evolution of the Greenland Ice Sheet (GrIS) and its contribution to sea-level rise. Widespread glacier acceleration has been linked to the warming of ocean waters around the periphery of Greenland but a lack of information on the bathymetry of the continental shelf and glacial fjords has limited our ability to understand how subsurface, warm, salty ocean waters of Atlantic origin (AW) reach the glaciers and melt them from below. Here, we employ high-resolution, airborne gravity data (AIRGrav) in combination with multibeam echo sounding (MBES) data, to infer the bathymetry of the coastal areas of Northwest Greenland for NASA's Ocean Melting Greenland (OMG) mission. High-resolution, AIRGrav data acquired on a 2 km spacing, 150 m ground clearance, with 1.5 mGal crossover error, is inverted in three dimensions to map the bathymetry. To constrain the inversion away from MBES data, we compare two methods: one based on the Direct Current (DC) shift of the gravity field (absolute minus observed gravity) and another based on the density of the bedrock. We evaluate and compare the two methods in areas with complete MBES coverage. We find the lowest standard error in bed elevation (±60 m) using the DC shift method. When applied to the entire coast of Northwest Greenland, the three-dimensional inversion reveals a complex network of connected sea bed channels, not known previously, that provide natural and varied pathways for AW to reach the glaciers across the continental shelf. The study demonstrates that the gravity approach offers an efficient and practical alternative to extensive ship mapping in ice-filled waters to obtain information critical to understanding and modeling ice-ocean interaction along ice sheet margins.

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Ocean‐Induced Melt Triggers Glacier Retreat in Northwest Greenland

Cited by 81 publications

References 41 publications

Modeling the response of northwest Greenland to enhanced ocean thermal forcing and subglacial discharge

Modeling the response of northwest Greenland to enhanced ocean thermal forcing and subglacial discharge

Drivers for Atlantic-origin waters abutting Greenland

Bathymetry of Northwest Greenland Using “Ocean Melting Greenland” (OMG) High-Resolution Airborne Gravity and Other Data

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