Bathymetry constrains ocean heat supply to Greenland’s largest glacier tongue

Schaffer, Janin; Kanzow, Torsten; Appen, Wilken-Jon von; Albedyll, Luisa von; Arndt, Jan Erik; Roberts, David H.

doi:10.1038/s41561-019-0529-x

Cited by 76 publications

(263 citation statements)

References 43 publications

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“…A specific deficiency in the literature to date is the absence of measured subglacial discharge rates from marineterminating glaciers. Variability in such rates on diurnal and seasonal timescales is expected (Schild et al, 2016;Fried et al, 2018), and intermittent periods of extremely high discharge are known to occur, for example from ice-dammed lake drainage in Godthåbsfjord (Kjeldsen et al, 2014). Yet determining the extent to which these events affect fjordscale mixing and biogeochemistry, as well as how these rates change in response to climate forcing, will require further field observations.…”

Section: Fjordmentioning

confidence: 99%

“…Carroll et al, 2016), do not yet consider such variability. Time lapse imagery shows that the lifetimes and spatial extents of subglacial discharge plumes can vary considerably (Schild et al, 2016;Fried et al, 2018). While buoyant plume theory has offered important insights into the role of subglacial plumes in the nutrient pump, buoyant plume theory does not characterize the lateral expansion of plume waters.…”

Section: A Need For New Approaches?mentioning

confidence: 99%

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Review article: How does glacier discharge affect marine biogeochemistry and primary production in the Arctic?

et al. 2020

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Abstract. Freshwater discharge from glaciers is increasing across the Arctic in response to anthropogenic climate change, which raises questions about the potential downstream effects in the marine environment. Whilst a combination of long-term monitoring programmes and intensive Arctic field campaigns have improved our knowledge of glacier–ocean interactions in recent years, especially with respect to fjord/ocean circulation, there are extensive knowledge gaps concerning how glaciers affect marine biogeochemistry and productivity. Following two cross-cutting disciplinary International Arctic Science Committee (IASC) workshops addressing the importance of glaciers for the marine ecosystem, here we review the state of the art concerning how freshwater discharge affects the marine environment with a specific focus on marine biogeochemistry and biological productivity. Using a series of Arctic case studies (Nuup Kangerlua/Godthåbsfjord, Kongsfjorden, Kangerluarsuup Sermia/Bowdoin Fjord, Young Sound and Sermilik Fjord), the interconnected effects of freshwater discharge on fjord–shelf exchange, nutrient availability, the carbonate system, the carbon cycle and the microbial food web are investigated. Key findings are that whether the effect of glacier discharge on marine primary production is positive or negative is highly dependent on a combination of factors. These include glacier type (marine- or land-terminating), fjord–glacier geometry and the limiting resource(s) for phytoplankton growth in a specific spatio-temporal region (light, macronutrients or micronutrients). Arctic glacier fjords therefore often exhibit distinct discharge–productivity relationships, and multiple case-studies must be considered in order to understand the net effects of glacier discharge on Arctic marine ecosystems.

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Section: Fjordmentioning

confidence: 99%

Section: A Need For New Approaches?mentioning

confidence: 99%

Review article: How does glacier discharge affect marine biogeochemistry and primary production in the Arctic?

et al. 2020

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“…A key component of the mass loss process, yet one whose quantification is still uncertain, is the contribution from the retreat of marine terminating glaciers forced by oceanic heat transport [79]. The ability of relatively warm waters to interact with marine terminating glaciers is often dependent on the presence or absence of bathymetric sills located under floating ice tongues [33,80], and thus the ability to map under ice-tongues is critical to understanding the fate of terminating glaciers. Additionally, the ability to map the location of grounding lines under ice shelves can provide critical insight into the history and dynamics of the ice sheets [30,31,35,81].…”

Section: Seafloor Mappingmentioning

confidence: 99%

Scientific Challenges and Present Capabilities in Underwater Robotic Vehicle Design and Navigation for Oceanographic Exploration Under-Ice

et al. 2020

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This paper reviews the scientific motivation and challenges, development, and use of underwater robotic vehicles designed for use in ice-covered waters, with special attention paid to the navigation systems employed for under-ice deployments. Scientific needs for routine access under fixed and moving ice by underwater robotic vehicles are reviewed in the contexts of geology and geophysics, biology, sea ice and climate, ice shelves, and seafloor mapping. The challenges of under-ice vehicle design and navigation are summarized. The paper reviews all known under-ice robotic vehicles and their associated navigation systems, categorizing them by vehicle type (tethered, untethered, hybrid, and glider) and by the type of ice they were designed for (fixed glacial or sea ice and moving sea ice).

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“…As the removal of the deep sill has a <1% effect on the yearly DIN transport, one could also consider this series of deep-sill simulations as variations on a sill-free fjord. We further note that, while basal melting is modeled, this study focuses on subglacial discharge effects, so this model system is not applicable to those where basal melting dominates freshwater budgets, like Nioghalvfjerdsfjorden Glacier (also known as the 79°N Glacier) or Petermann Glacier, which are characterized by long floating ice tongues (Münchow et al, 2014;Schaffer et al, 2020).…”

Section: Applicabilitymentioning

confidence: 99%

“…Models suggest that the export of meltwater from fjords depends on fjord width, grounding line depth, and sill height (Carroll et al, 2016(Carroll et al, , 2017. Baroclinic flows driven by density fluctuations on the shelf, or "shelf forcing," are also important to volume transport and exchange between fjords and the shelf (e.g., Jackson et al, 2014;Schaffer et al, 2020;Sutherland et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Meltwater‐Enhanced Nutrient Export From Greenland's Glacial Fjords: A Sensitivity Analysis

et al. 2020

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As mass loss from the Greenland Ice Sheet accelerates, this modeling study considers how meltwater inputs to the ocean can impact marine ecosystems using a simplified fjord scenario. At marine‐terminating glaciers in Greenland fjords, meltwater can be delivered far below the sea surface, both as subglacial runoff (from atmosphere‐driven surface melt) and as basal melt (from ocean heat). Such delivery can result in buoyancy‐driven upwelling and the upward entrainment of nutrient‐rich deep water, which can support phytoplankton growth in fjord surface waters. For this study, we use an idealized fjord‐scale model to investigate which properties of glaciers and fjords govern the transport of buoyantly upwelled nutrients from fjords. We model the influence of fjord geometry, hydrology, wind, tides, and phytoplankton growth within the fjord on meltwater‐driven nutrient export to the ocean. We use the Regional Ocean Modeling System (ROMS) coupled to a buoyant plume model and a biogeochemical model to simulate physical and biogeochemical processes within an idealized tidewater glacial fjord. Results show that meltwater‐driven nutrient export increases with larger subglacial discharge rates and deeper grounding lines, features that are both likely to change with continued ice sheet melting. Nutrient export decreases with longer residence times, allowing greater biological drawdown. While the absence of a coastal current in the model setup prevents the downstream advection of exported nutrients, results suggest that shelf‐forced flows could influence nutrient residence time within fjords. This simplified model highlights key uncertainties requiring further observation to understand ecological impacts of Greenland mass loss.

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Bathymetry constrains ocean heat supply to Greenland’s largest glacier tongue

Cited by 76 publications

References 43 publications

Review article: How does glacier discharge affect marine biogeochemistry and primary production in the Arctic?

Review article: How does glacier discharge affect marine biogeochemistry and primary production in the Arctic?

Scientific Challenges and Present Capabilities in Underwater Robotic Vehicle Design and Navigation for Oceanographic Exploration Under-Ice

Meltwater‐Enhanced Nutrient Export From Greenland's Glacial Fjords: A Sensitivity Analysis

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