Calving rates at tidewater glaciers vary strongly with ocean temperature

Luckman, Adrian; Benn, Douglas I.; Cottier, Finlo; Bevan, Suzanne; Nilsen, Frank; Inall, Mark

doi:10.1038/ncomms9566

Cited by 273 publications

(316 citation statements)

References 36 publications

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“…Increased melt water through a warmer atmosphere can lead to increased lubrication that speeds up glaciers and increases discharge (30)(31)(32). We here assume that frontal stress release (54) and runoff lubrication (27) can be approximated as linearly depending the global mean temperature anomaly ΔT. Ref.…”

Section: Methodsmentioning

confidence: 99%

Future sea level rise constrained by observations and long-term commitment

Mengel

Levermann

Frieler

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

182

169

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Sea level has been steadily rising over the past century, predominantly due to anthropogenic climate change. The rate of sea level rise will keep increasing with continued global warming, and, even if temperatures are stabilized through the phasing out of greenhouse gas emissions, sea level is still expected to rise for centuries. This will affect coastal areas worldwide, and robust projections are needed to assess mitigation options and guide adaptation measures. Here we combine the equilibrium response of the main sea level rise contributions with their last century's observed contribution to constrain projections of future sea level rise. Our model is calibrated to a set of observations for each contribution, and the observational and climate uncertainties are combined to produce uncertainty ranges for 21st century sea level rise. We project anthropogenic sea level rise of 28-56 cm, 37-77 cm, and 57-131 cm in 2100 for the greenhouse gas concentration scenarios RCP26, RCP45, and RCP85, respectively. Our uncertainty ranges for total sea level rise overlap with the process-based estimates of the Intergovernmental Panel on Climate Change. The "constrained extrapolation" approach generalizes earlier global semiempirical models and may therefore lead to a better understanding of the discrepancies with processbased projections. 2) with a rate of around 3 cm per decade since 1990 (3, 4). Thermal expansion of the oceans and retreating glaciers are the main contributors to sea level rise in the past century and the near future. On multicentennial timescales, the Greenland and Antarctic ice sheets will likely dominate global sea level rise (5). Future sea level rise will pose challenges to coastal regions around the globe, and robust projections are needed to guide adaptation investment and provide incentives for climate mitigation (6).Projecting sea level relies on the understanding of the processes that drive sea level changes and on reliable data to verify and calibrate models. So-called process-based models now deliver projections for the main components of climate-driven sea level rise-thermal expansion, glaciers and ice caps, the Greenland ice sheet, and the Antarctic ice sheet-although solid ice discharge (SID) from the ice sheets is still difficult to constrain (3). Semiempirical models follow a different approach and use the statistical relation between global mean temperature (7,8) or radiative forcing (9, 10) and sea level from past observations. Without aiming to capture the full physics of the sea level components, they project future sea level assuming that the past statistical relation also holds in the future. Their simpler nature makes them feasible for probabilistic assessments and makes their results easier to reproduce.The long-term multicentennial to millennial sensitivity of the main individual sea level contributors to global temperature changes can be constrained by paleoclimatic data and is more easily computed with currently available process-based large-scale models than are decadal to centenn...

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Section: Methodsmentioning

confidence: 99%

Future sea level rise constrained by observations and long-term commitment

Mengel

Levermann

Frieler

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

182

169

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“…Ice surface velocities were derived from feature tracking of TerraSAR-X image pairs in slant range using correlation windows of 200×200 pixels at every 20 pixels, and subsequently ortho-rectified to a pixel size of 40 m using a digital elevation model (Luckman et al, 2015). Acquisition is done roughly every 11 days for the period May-October 2013.…”

Section: Observed Surface Velocities and Front Positionsmentioning

confidence: 99%

“…Since 2011, the summer retreat has outpaced the winter advance, with an overall net retreat of ∼2 km between 2011 and 2015 after a relatively stable period since the 1990s (Schellenberger et al, 2015;Luckman et al, 2015;Köhler et al, 2016). Velocities at the front can reach 5 m d −1 in the summer with large seasonal and annual variations associated with basal sliding .…”

mentioning

confidence: 99%

“…Close to the subglacial discharge locations, a changing grounding-line fan of sediments has been observed (Trusel et al, 2010) potentially ensuring a pinning point if the glacier were to advance in the future. Luckman et al (2015) showed that calving rates are strongly correlated with subsurface fjord temperatures, indicating that the dominant control on calving is melt undercutting, followed by collapse of the sub-aerial part. …”

mentioning

confidence: 99%

“…Even when the melt season 15 is finished, the drainage system is still influencing the dynamics and the calving. Luckman et al (2015) showed that frontal ablation rates have the strongest correlation with ocean temperature in the fjord at the season timescale and the correlation with ice velocity appears when velocity is high. Our experiments are not including the varying fjord water temperature and limit our discussion on that subject but the velocity higher at the front than further inland seem in agreement with Luckman et al…”

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confidence: 99%

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Effects of undercutting and sliding on calving: a coupled approach applied to Kronebreen, Svalbard

Vallot¹,

Åström²,

Zwinger³

et al. 2017

Preprint

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Abstract.In this paper, we study the effects of basal friction, sub-aqueous undercutting and glacier geometry on the calving process with six different models: a continuum-mechanical ice flow model (Elmer/Ice), a climatic mass balance model, a simple subglacial hydrology model, a plume model, an undercut model and a discrete particle model to investigate fracture dynamics (Helsinki Discrete Element Model, HiDEM). We also demonstrate the feasibility of reproducing the observed calving retreat 5 at the front of Kronebreen, a tidewater glacier in Svalbard, during a melt season. Basal sliding and glacier motion is addressed using Elmer/Ice while calving is modelled by HiDEM. An hydrology model calculates subglacial drainage paths and indicates two main outlets at relatively different rates. Depending on the discharge, the plume model computes frontal melt rates, which are iteratively projected to the actual front of the glacier at subglacial discharge locations. This produces undercutting of different sizes, as melt is concentrated close to the surface for high discharge and is more diffuse for low discharge. By testing 10 different configurations, we show that the geometry (frontal position and topography) controls the calving location while basal sliding controls the calving rate. Undercutting plays a key role in glacier retreat and is necessary to reproduce observed retreat in the vicinity of the discharge location.

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Modeling of ocean‐induced ice melt rates of five west Greenland glaciers over the past two decades

Rignot

Menemenlis

et al. 2016

Geophysical Research Letters

114

153

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High‐resolution, three‐dimensional simulations from the Massachusetts Institute of Technology general circulation model ocean model are used to calculate the subaqueous melt rate of the calving faces of Umiamako, Rinks, Kangerdlugssup, Store, and Kangilerngata glaciers, west Greenland, from 1992 to 2015. Model forcing is from monthly reconstructions of ocean state and ice sheet runoff. Results are analyzed in combination with observations of bathymetry, bed elevation, ice front retreat, and glacier speed. We calculate that subaqueous melt rates are 2–3 times larger in summer compared to winter and doubled in magnitude since the 1990s due to enhanced subglacial runoff and 1.6 ± 0.3°C warmer ocean temperature. Umiamako and Kangilerngata retreated rapidly in the 2000s when subaqueous melt rates exceeded the calving rates and ice front retreated to deeper bed elevation. In contrast, Store, Kangerdlugssup, and Rinks have remained stable because their subaqueous melt rates are 3–4 times lower than their calving rates, i.e., the glaciers are dominated by calving processes.

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Calving rates at tidewater glaciers vary strongly with ocean temperature

Cited by 273 publications

References 36 publications

Future sea level rise constrained by observations and long-term commitment

Future sea level rise constrained by observations and long-term commitment

Effects of undercutting and sliding on calving: a coupled approach applied to Kronebreen, Svalbard

Modeling of ocean‐induced ice melt rates of five west Greenland glaciers over the past two decades

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