Pathways, Form Drag, and Turbulence in Simulations of an Ocean Flowing Through an Ice Mélange

Hughes, Kenneth G.

doi:10.1029/2021jc018228

Cited by 6 publications

(3 citation statements)

References 64 publications

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“…These results are consistent with prior studies at Sermeq Kujalleq, which found strong glacier‐mélange linkages and weak to null mélange‐ocean current linkages (Amundson et al., 2010; Cassotto et al., 2021). Additionally, modeled outputs suggest that surface currents in a mélange are greatly reduced, and instead of flowing at the surface, the down‐fjord flow is located below the drafts of the deepest icebergs (Hughes, 2022). Therefore, due to the tightly packed nature of the mélange and the forced location of the currents, tracking icebergs in the mélange region is not representative of fjord circulation and we exclude the mélange region in analysis of surface circulation.…”

Section: Discussionmentioning

confidence: 99%

Ilulissat Icefjord Upper‐Layer Circulation Patterns Revealed Through GPS‐Tracked Icebergs

Baratta,

Schild,

Sutherland

2024

JGR Oceans

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The Greenland Ice Sheet has undergone rapid mass loss over the last four decades, primarily through solid and liquid discharge at marine‐terminating outlet glaciers. The acceleration of these glaciers is in part due to the increase in temperature of ocean water in contact with the glacier terminus. However, quantifying heat transport to the glacier through fjord circulation can be challenging due to iceberg abundance, which threatens instrument survival and fjord accessibility. Here we utilize iceberg movement to infer upper‐layer fjord circulation, as freely floating icebergs (i.e., outside the mélange region) behave as natural drifters. In the summers of 2014 and 2019, we deployed transmitting GPS units on a total of 13 icebergs in Ilulissat Icefjord, an iceberg‐rich and historically data‐poor fjord in west Greenland, to quantify circulation over the upper 0–250 m of the water column. We find that the direction of upper‐layer fjord circulation is strongly impacted by the timing of tributary meltwater runoff, while the speed of this circulation changes in concert with glacier behavior, which includes increases and decreases in glacier speed and meltwater runoff. During periods of increased meltwater runoff entering from tributary fjords, icebergs at these confluences deviated from their down‐fjord trajectory, even reversing up‐fjord, until the runoff pulse subsided days later. This study demonstrates the utility of iceberg monitoring to constrain upper‐layer fjord circulation, and highlights the importance of including tributary fjords in predictive models of heat transport and fjord circulation.

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Section: Discussionmentioning

confidence: 99%

Ilulissat Icefjord Upper‐Layer Circulation Patterns Revealed Through GPS‐Tracked Icebergs

Baratta,

Schild,

Sutherland

2024

JGR Oceans

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“…found strong glacier-mélange linkages and weak to null mélange-ocean current linkages (Amundson et al, 2010;Cassotto et al, 2021). Additionally, modeled outputs suggest that surface currents in a mélange are greatly reduced, and instead of flowing at the surface, the down-fjord flow is located below the drafts of the deepest icebergs (Hughes, 2022). Therefore, due to the tightly packed nature of the mélange and the forced location of the currents, tracking icebergs in the mélange region is not representative of fjord circulation and we exclude the mélange region in analysis of surface circulation.…”

Section: Discussionmentioning

confidence: 99%

Ilulissat Icefjord Upper-Layer Circulation Patterns Revealed through GPS-Tracked Icebergs

Baratta,

Schild,

Sutherland

2023

Preprint

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Wood et al., 2021). Jakobshavn Isbrae (here after referred to by its Greenlandic name, Sermeq Kujalleq) has been the largest single contributor to GrIS mass loss since 2000 (Mouginot et al., 2019), and has undergone a series of dramatic changes, including a 15 km retreat of its floating ice tongue between 1991 and 2006, before pinning to the present-day location. Warming shelf water has been implicated in the changes observed at Sermeq Kujalleq (ice tongue retreat, glacier acceleration, increases in calving; e.g.,

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“…Very high‐resolution (<10 m) models have brought insight into the dynamics of subglacial discharge plumes (e.g., Carroll et al., 2015; Ezhova et al., 2017; Kimura et al., 2014; Sciascia et al., 2013; Xu et al., 2012) and led to plume representation into larger fjord models (T. Cowton et al., 2015; Jenkins, 2011; Rignot et al., 2016). Fjord‐scale models have allowed for an assessment of the impact of along‐fjord winds, along‐shelf winds and shelf forcing on fjord dynamics (Fraser & Inall, 2018; Jackson et al., 2018; Sundfjord et al., 2017), of iceberg melt on water mass transformation (Davison et al., 2020; Kajanto et al., 2023), of sea ice retreat on fjord circulation (Shroyer et al., 2017), and of fjord geometry, including ice mélange, on fjord renewal (Gladish, Holland, Rosing‐Asvid, et al., 2014; Carroll et al., 2017; Zhao et al., 2021; K. G. Hughes, 2022). While these models have significantly improved our understanding of glacial fjord processes, they are usually run on idealized bathymetry or with idealized forcing limiting any comparison with observations.…”

Section: Introductionmentioning

confidence: 99%

Relative Roles of Plume and Coastal Forcing on Exchange Flow Variability of a Glacial Fjord

Sanchez,

Straneo,

Hughes

et al. 2024

JGR Oceans

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Glacial fjord circulation determines the import of oceanic heat to the Greenland Ice Sheet and the export of ice sheet meltwater to the ocean. However, limited observations and the presence of both glacial and coastal forcing—such as coastal‐trapped waves—make uncovering the physical mechanisms controlling fjord‐shelf exchange difficult. Here we use multi‐year, high‐resolution, realistically forced numerical simulations of Sermilik Fjord in southeast Greenland to evaluate the exchange flow. We compare models, with and without a plume, to differentiate between the exchange flow driven by shelf variability and that driven by subglacial discharge. We use the Total Exchange Flow framework to quantify the exchange volume transports. We find that a decline in offshore wind stress from January through July drives a seasonal reversal in the exchange flow increasing the presence of warm Atlantic Water at depth. We also find that including glacial plumes doubles the exchange flow in the summer. Our results show that the plume‐driven circulation is more effective at renewal with a flushing time 1/3 that of the shelf‐driven circulation near the fjord head.

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Pathways, Form Drag, and Turbulence in Simulations of an Ocean Flowing Through an Ice Mélange

Cited by 6 publications

References 64 publications

Ilulissat Icefjord Upper‐Layer Circulation Patterns Revealed Through GPS‐Tracked Icebergs

Ilulissat Icefjord Upper‐Layer Circulation Patterns Revealed Through GPS‐Tracked Icebergs

Ilulissat Icefjord Upper-Layer Circulation Patterns Revealed through GPS-Tracked Icebergs

Relative Roles of Plume and Coastal Forcing on Exchange Flow Variability of a Glacial Fjord

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