Local Coastal Water Masses Control Heat Levels in a West Greenland Tidewater Outlet Glacier Fjord

Mortensen, John; Rysgaard, Søren; Arendt, Kristine Engel; Juul-Pedersen, Thomas; Søgaard, Dorte Haubjerg; Bendtsen, Jørgen; Meire, Lorenz

doi:10.1029/2018jc014549

Cited by 32 publications

(66 citation statements)

References 31 publications

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“…Furthermore, troughs in this region are generally shallow (<300-m depth), which makes it difficult for dSPMW to find a pathway through the continental shelf. This observation is confirmed by a recent study from Godthåbsfjord, which highlights that CW seasonally restricts SPMW from entering the fjord (Mortensen et al, 2018). This may be a general feature of the southern Greenland fjords.…”

Section: The Regional Heat Source For Melting Glacierssupporting

confidence: 82%

“…Using our findings above, another explanation might be that the lack of BBPW on the Southwest Greenland coast in 2010 explain an increased accumulation of BBPW on the Northwest Greenland coast and in Disko Bay in the absence of seasonal southward transport of BBPW, giving rise to distinct low temperatures in Ilulissat Icefjord basin waters. Contrary to this, Godthåbsfjord experienced distinct high temperatures in 2010 (Mortensen et al, ). Where Khazendar et al () attribute cooling of the regional heat source (i.e., dSPMW) to a slowdown and thickening of Jakobshavn Isbrae in Disko Bay, our observations suggest that a more voluminous BBPW in Disko Bay may be responsible for the cooling by squeezing dSPMW to a deeper depth range.…”

Section: Resultsmentioning

confidence: 99%

“…Recent studies have either focused on the hydrographic conditions on the coast or in fjords and their links to these changes. Few studies, however, have covered the links between the coastal system and fjords with marine‐terminating glaciers (Carroll et al, ; Gladish et al, ; Mortensen et al, ; Straneo et al, ). Distinct seasonal hydrographic differences are observed between the coast and outer and inner fjords (Mortensen et al, ).…”

Section: Introductionmentioning

confidence: 99%

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An Updated View on Water Masses on the pan‐West Greenland Continental Shelf and Their Link to Proglacial Fjords

et al. 2020

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The accelerated melt of the Greenland Ice Sheet has been linked to a sudden increase in the presence of warm subsurface coastal water in west Greenland. Yet pathways of warm coastal water along the entire west Greenland coast have remained largely unstudied. Here we present the first, near‐synoptic hydrographic observations at both the continental slope and fjord entrances of the west Greenland coastal system from Cape Farewell (59°N) to Melville Bay (75°N) in summer 2016. We observed a distinct north‐south division in the water mass distribution in west Greenland, approximately partitioned by the northern part of Davis Strait, and a division between the continental slope and fjord entrances. Waters from the regional southern freshwater source with origin in the East Greenland Current that rounds Cape Farewell are not observed to enter Baffin Bay. The regional heat source transported by the West Greenland Current is blocked by Southwest Greenland Coastal Water in the south but the deep connections in the north allow warm deep Subpolar Mode Water to enter fjords. Furthermore, we observed cold and relative saline Baffin Bay Polar Water over the inner part of the banks, periodically reaching as far south as 64°N, suggesting the presence of an undescribed southward current at the Southwest Greenland continental shelf.

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Section: The Regional Heat Source For Melting Glacierssupporting

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An Updated View on Water Masses on the pan‐West Greenland Continental Shelf and Their Link to Proglacial Fjords

et al. 2020

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“…In recent decades, fjord-terminating glaciers have been rapidly losing mass (Larsen et al, 2007;Pritchard et al, 2009), contributing significantly to eustatic sea level rise (Gardner et al, 2013;McNabb and Hock, 2014). High volumes of ice discharge due to iceberg calving and submarine melt have been attributed to contact between the glacier terminus and relatively warm and salty fjord waters (Bartholomaus et al, 2013;Motyka et al, 2003). Current fjord circulation models do not take icebergs into account, though icebergs may modify warm, dense waters entering the fjord by enhancing vertical mixing and by extracting heat through iceberg melt (Carroll et al, 2015;Klinck et al, 1981;Mortensen et al, 2018;Motyka et al, 2003;Rignot et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal distributions of icebergs in a temperate fjord: Columbia Fjord, Alaska

2019

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Abstract. Much of the world's ice enters the ocean via outlet glaciers terminating in fjords. Inside fjords, icebergs may affect glacier–ocean interactions by cooling incoming ocean waters, enhancing vertical mixing, or providing back stress on the terminus. However, relatively few studies have been performed on iceberg dynamics inside fjords, particularly outside of Greenland. We examine icebergs calved from Columbia Glacier, Alaska, over 8 months spanning late winter to mid-fall using 0.5 m resolution satellite imagery, identifying icebergs based on pixel brightness. Iceberg sizes fit a power-law distribution with an overall power-law exponent, m, of -1.26±0.05. Seasonal variations in the power-law exponent indicate that brittle fracture of icebergs is more prevalent in the summer months. Combining our results with those from previous studies of iceberg distributions, we find that iceberg calving rate, rather than water temperature, appears to be the major control on the exponent value. We also analyze icebergs' spatial distribution inside the fjord and find that large icebergs (10 000–100 000 m2 cross-sectional area) have low spatial correlation with icebergs of smaller sizes due to their tendency to ground on shallow regions. We estimate the surface area of icebergs in contact with incoming seawater to be 3.0±0.63×104 m2. Given the much larger surface area of the terminus, 9.7±3.7×105 m2, ocean interactions with the terminus may have a larger impact on ocean heat content than interactions with icebergs.

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“…High volumes of ice discharge due to iceberg calving and submarine melt have been attributed to contact with relatively warm and salty fjord 25 waters ( Bartholomaus et al, 2013;Motyka et al, 2003). Current fjord circulation models do not take icebergs into account, though icebergs may modify warm, dense waters entering the fjord by enhancing vertical mixing and heat extraction accompanying iceberg melt (Carroll et al, 2015;Klinck et al, 1981;Mortensen et al, 2018;Motyka et al, 2003;Rignot et al, 2010). Various studies have examined the iceberg calving process (Bahr, 1995;Chapuis and Tetzlaff, 2014;Hughes, 2002;O'Neel et al, 2003;Warren et al, 2001), as well as the transport and evolution of icebergs in the open ocean (Bigg et 30 The Cryosphere Discuss., https://doi.org /10.5194/tc-2018-230 Manuscript under review for journal The Cryosphere Discussion started: 8 January 2019 c Author(s) 2019.…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal Distributions of Icebergs in a Temperate Fjord: Columbia Fjord, Alaska

Neuhaus¹,

Tulaczyk²,

Begeman³

2019

Preprint

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Abstract. Fjord-terminating glaciers account for the majority of recent sea level rise. Inside fjords, icebergs may affect glacier-ocean interactions by cooling incoming ocean waters, enhancing vertical mixing, or by providing back stress on the terminus. However, relatively few studies have been performed on iceberg dynamics inside fjords, particularly outside of Greenland. We examine icebergs calved from Columbia Glacier, Alaska, over eight months spanning late winter to mid-fall using 0.5-meter resolution satellite imagery, identifying icebergs based on pixel brightness. Iceberg sizes fit a power-law distribution with an overall power-law exponent, m, of −1.26 ± 0.05. We find that iceberg calving rate, rather than water temperature, appears to be the major control on the exponent value. We also examine iceberg spatial distribution inside the fjord, and find that large icebergs (10,000 m2 − 100,000 m2 cross-sectional area) have low spatial correlation with icebergs of smaller sizes (correlation coefficients between 0.345 ± 0.132 and 0.490 ± 0.114, compared to 0.809 ± 0.052 − 0.989 ± 0.006 for the highly spatially-correlated smaller icebergs), due to their tendency to ground on the shallows. We estimate the surface area of icebergs in contact with incoming seawater to be 2.8 ± 0.58 × 104 m2. When compared with our estimated terminus surface area, 9.7 ± 3.7 × 105 m2, we expect iceberg impact on the heat content of the incoming seawater to be negligible in this fjord. Additionally, we find mechanical buttressing of the glacier to be negligible due to low iceberg density near the calving front and lack of winter sea ice in the fjord.

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Local Coastal Water Masses Control Heat Levels in a West Greenland Tidewater Outlet Glacier Fjord

Cited by 32 publications

References 31 publications

An Updated View on Water Masses on the pan‐West Greenland Continental Shelf and Their Link to Proglacial Fjords

An Updated View on Water Masses on the pan‐West Greenland Continental Shelf and Their Link to Proglacial Fjords

Spatiotemporal distributions of icebergs in a temperate fjord: Columbia Fjord, Alaska

Spatiotemporal Distributions of Icebergs in a Temperate Fjord: Columbia Fjord, Alaska

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