Icebergs and Sea Ice Detected with Inverted Echo Sounders

Andres, Magdalena; Silvano, Alessandro; Straneo, Fiammetta; Watts, D. Randolph

doi:10.1175/jtech-d-14-00161.1

Cited by 14 publications

(27 citation statements)

References 28 publications

(23 reference statements)

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“…The observed velocities agree well with previous studies of icebergs in both open water (Smith, 1993) and other fjords in Greenland (Sutherland et al, 2014;Andres et al, 2015). The looping behavior observed is similar to those observed by Sutherland et al (2014).…”

Section: Discussionsupporting

confidence: 91%

“…Recent studies have focused on large (>100 m) icebergs in Greenland waters as icebergs of this scale are easier to detect using remote sensing (Buus-Hinkler et al, 2014;Enderlin and Hamilton, 2014;Enderlin et al, 2016;Sulak et al, 2017) and in situ (Andres et al, 2015) techniques. While such data provide important information about volumes, distributions and the geographical extent of icebergs, they do not provide information about transport.…”

Section: Introductionmentioning

confidence: 99%

“…While such data provide important information about volumes, distributions and the geographical extent of icebergs, they do not provide information about transport. Measurements of iceberg trajectories in Greenlandic fjords are somewhat limited (Amundson et al, 2010;Sutherland et al, 2014;Andres et al, 2015;FitzMaurice et al, 2016). GPS-based observations in fjords (Sutherland et al, 2014;Sulak et al, 2017) and in Baffin Bay (Wagner et al, 2014;Larsen et al, 2015) are biased toward larger and, presumably, more stable icebergs.…”

Section: Introductionmentioning

confidence: 99%

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Bergy Bit and Melt Water Trajectories in Godthåbsfjord (SW Greenland) Observed by the Expendable Ice Tracker

et al. 2017

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Icebergs and bergy bits makes up a significant component of the total freshwater flux from the Greenland Ice Sheet to the ocean. Observations of iceberg trajectories are biased toward larger icebergs and, as a result, the drift characteristics of smaller icebergs and bergy bits are poorly understood. In an attempt to fill this critical knowledge gap, we developed the open-source EXpendable Ice TrackEr (EXITE). EXITE is a low-cost, satellite-tracked GPS beacon capable of high-resolution temporal measurements over extended deployment periods (30 days or more). Furthermore, EXITE can transform to a surface drifter when its host iceberg capsizes or fragments. Here we describe basic construction of an EXITE beacon and present results from a deployment in Godthåbsfjord (SW Greenland) in August 2016. Overall, EXITE trajectories show out-fjord surface transport, in agreement with a simple estuarine circulation paradigm. However, eddies and abrupt wind-driven reversals reveal complex surface transport pathways at time scales of hours to days.

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Section: Discussionsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Bergy Bit and Melt Water Trajectories in Godthåbsfjord (SW Greenland) Observed by the Expendable Ice Tracker

et al. 2017

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“…Sermilik Fjord is also subjected to intense, localized along-fjord wind events from downslope flow off the ice sheet (Oltmanns et al 2014). The fjord is only rarely covered by land-fast sea ice (Andres et al 2015).…”

Section: A Background On Sermilik Fjord Regionmentioning

confidence: 99%

Heat, Salt, and Freshwater Budgets for a Glacial Fjord in Greenland

Jackson

Straneo

2016

Journal of Physical Oceanography

134

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In Greenland's glacial fjords, heat and freshwater are exchanged between glaciers and the ocean. Submarine melting of glaciers has been implicated as a potential trigger for recent glacier acceleration, and observations of ocean heat transport are increasingly being used to infer the submarine melt rates. The complete heat, salt, and mass budgets that underlie such methods, however, have been largely neglected. Here, a new framework for exploring glacial fjord budgets is developed. Building on estuarine studies of salt budgets, the heat, salt, and mass transports through the fjord are decomposed, and new equations for calculating freshwater fluxes from submarine meltwater and runoff are presented. This method is applied to moored records from Sermilik Fjord, near the terminus of Helheim Glacier, to evaluate the dominant balances in the fjord budgets and to estimate freshwater fluxes. Throughout the year, two different regimes are found. In the nonsummer months, advective transports are balanced by changes in heat/salt storage within their ability to measure; freshwater fluxes cannot be inferred as a residual. In the summer, a mean exchange flow emerges, consisting of inflowing Atlantic water and outflowing glacially modified water. This exchange transports heat toward the glacier and is primarily balanced by changes in storage and latent heat for melting ice. The total freshwater flux increases over the summer, reaching 1200 6 700 m 3 s 21 of runoff and 1500 6 500 m 3 s 21 of submarine meltwater from glaciers and icebergs in August. The methods and results highlight important components of fjord budgets, particularly the storage and barotropic terms, that have been not been appropriately considered in previous estimates of submarine melting.

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“…This is not too surprising, given the thick ice melange and deep iceberg keels that extend into the warm Atlantic Water layer (Andres et al, 2015). However, it is contrary to the assumption of most previous studies that iceberg melting is small compared to glacier melting.…”

Section: Future Directionsmentioning

confidence: 77%

Dynamics of Greenland�s glacial fjords

Jackson¹

2016

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Glacial fjords form conduits between glaciers of the Greenland Ice Sheet and the North Atlantic. They are the gateways for importing oceanic heat to melt ice and for exporting meltwater into the ocean. Submarine melting in fjords has been implicated as a driver of recent glacier acceleration; however, there are no direct measurements of this melting, and little is known about the fjord processes that modulate melt rates. Combining observations, theory, and modeling, this thesis investigates the circulation, heat transport, and meltwater export in glacial fjords.While most recent studies focus on glacial buoyancy forcing, there are other drivers -e.g. tides, local wind, shelf variability -that can be important for fjord circulation. Using moored records from two major Greenlandic fjords, shelf forcing (from shelf density fluctuations) is found to dominate the fjord circulation, driving rapid exchange with the shelf and large heat content variability near the glacier. Contrary to the conventional paradigm, these flows mask any glacier-driven circulation in the non-summer months. During the summer, when shelf forcing is reduced and freshwater forcing peaks, a mean exchange flow transports warm Atlantic-origin water towards the glacier and exports glacial meltwater.Many recent studies have inferred submarine melt rates from oceanic heat transport, but the fjord budgets that underlie this method have been overlooked. Building on estuarine studies of salt fluxes, this thesis presents a new framework for assessing glacial fjord budgets and revised equations for inferring meltwater fluxes. Two different seasonal regimes are found in the heat/salt budgets for Sermilik Fjord, and the results provide the first time-series of submarine meltwater and subglacial discharge fluxes into a glacial fjord.Finally, building on the observations, ROMS numerical simulations and two analytical models are used to investigate the dynamics of shelf-driven flows and their importance relative to local wind forcing across the parameter space of Greenland's fjords. The fjord response is found to vary primarily with the width relative to the deformation radius and the fjord adjustment timescale relative to the forcing timescale. Understanding these modes of circulation is a step towards accurate modeling of ocean-glacier interactions.

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Icebergs and Sea Ice Detected with Inverted Echo Sounders

Cited by 14 publications

References 28 publications

Bergy Bit and Melt Water Trajectories in Godthåbsfjord (SW Greenland) Observed by the Expendable Ice Tracker

Bergy Bit and Melt Water Trajectories in Godthåbsfjord (SW Greenland) Observed by the Expendable Ice Tracker

Heat, Salt, and Freshwater Budgets for a Glacial Fjord in Greenland

Dynamics of Greenland�s glacial fjords

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