Vulnerability of Denman Glacier to Ocean Heat Flux Revealed by Profiling Float Observations

Wijk, Esmee van; Rintoul, Stephen R.; Wallace, Luke; Ribeiro, Natalia; Herráiz‐Borreguero, Laura

doi:10.1029/2022gl100460

Cited by 11 publications

(14 citation statements)

References 40 publications

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“…MCDW intrusions have been observed on the East Antarctic continental slope (Bindoff et al, 2000;Foppert et al, 2019) and several parts of the continental shelf, including in the surroundings of the Totten Glacier (Williams et al, 2011;Rintoul et al, 2016;Silvano et al, 2017), the Denman Glacier (van Wijk et al, 2022), and the Amery Ice Shelf (Herraiz-Borreguero et al, 2015;Guo et al, 2022). Bottom temperatures simulated by WAOM (Figures 9D-F) are generally within the observed range, indicating MCDW intrusion in many locations of the East Antarctica sector.…”

Section: Water Mass Transformation Under the East Antarctica Ice Shelvesmentioning

confidence: 69%

Sensitivity of simulated water mass transformation on the Antarctic shelf to tides, topography and model resolution

et al. 2023

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Water mass transformation (WMT) around the Antarctic margin controls Antarctica Bottom Water formation and the abyssal limb of the global meridional overturning circulation, besides mediating ocean-ice shelf exchange, ice sheet stability and its contribution to sea level rise. However, the mechanisms controlling the rate of WMT in the Antarctic shelf are poorly understood due to the lack of observations and the inability of climate models to simulate those mechanisms, in particular beneath the floating ice shelves. We used a circum-Antarctic ocean-ice shelf model to assess the contribution of surface fluxes, mixing, and ocean-ice shelf interaction to the WMT on the continental shelf. The salt budget dominates the WMT rates, with only a secondary contribution from the heat budget. Basal melt of ice shelves drives buoyancy gain at lighter density classes (27.2<σθ< 27.6 kg m-3), while salt input associated with sea-ice growth in coastal polynyas drives buoyancy loss at heavier densities (σθ> 27.6). We found a large sensitivity of the WMT rates to model horizontal resolution, tides and topography within the Filchner-Ronne, East and West Antarctica ice shelf cavities. In the Filchner-Ronne Ice Shelf, an anticyclonic circulation in front of the Ronne Depression regulates the rates of basal melting/refreezing and WMT and is substantially affected by tides and model resolution. Model resolution is also found to affect the Antarctic Slope Current in both East and West Antarctica, impacting the on-shelf heat delivery, basal melt and WMT. Moreover, the representation of the ice shelf draft associated with model resolution impacts the freezing temperature and thus basal melt and WMT rates in the East Antarctica. These results highlight the importance of resolving small-scale features of the flow and topography, and to include the effects of tidal forcing, to adequately represent water mass transformations on the shelf that directly influence the abyssal global overturning circulation.

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Section: Water Mass Transformation Under the East Antarctica Ice Shelvesmentioning

confidence: 69%

Sensitivity of simulated water mass transformation on the Antarctic shelf to tides, topography and model resolution

et al. 2023

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“…In this region, the eddy conditions have recently been explored (FRE19; Stewart et al., 2018), wherein lateral tidal mixing is known to be weaker than that in the rest of the Antarctic margin (Padman et al., 2018), and the frontal structure of the ASC is relatively prominent (Pauthenet et al., 2021). The onshore CDW flux toward East Antarctica is collecting attention as a cause of glacial melting (e.g., van Wijk et al., 2022).…”

Section: Introductionmentioning

confidence: 99%

Diffusion of Circumpolar Deep Water Towards Antarctica

2023

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Throughout the Antarctic Circumpolar Current (ACC), mesoscale eddies transport water masses across time-mean streamlines, comprising the adiabatic pathway of the global meridional overturning circulation (Cessi, 2019;Marshall & Radko, 2003). Isopycnal eddy diffusion is fundamental for the poleward heat flux across the ACC because bottom-enhanced diapycnal mixing (Kunze et al., 2006) and surface water transformation (Abernathey et al., 2016) are unlikely to penetrate the intermediate and deep layers. Recent observations have indicated that mesoscale eddies play a key role in bridging the Antarctic meridional overturning from deep ocean basins to continental shelves (e.g., Mckee et al., 2019;Yamazaki et al., 2021), but its regime transition and transporting flux from the ACC to the Antarctic Slope Current (ASC) largely remains unknown from an observational standpoint (Thompson et al., 2018).Circumpolar Deep Water (CDW), the primary source of heat and salt for the Antarctic coasts, is transported across the ASC predominantly by mesoscale eddies in the absence of large-scale zonal pressure gradients (Stewart &

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“…Geophysical observations have shown that extensive portions of the EAIS rest on bedrock below sea level (Fretwell et al., 2013). Oceanographic observations have demonstrated that relatively warm waters reach the calving fronts of glaciers that provide the major drainages of the EAIS, including the Totten Glacier (Rintoul et al., 2016; Silvano et al., 2017), the Vanderford Glacier (Herraiz‐Borreguero & Naveira Garabato, 2022; Ribeiro et al., 2021), and the Denman Glacier (Brancato et al., 2020; van Wijk et al., 2022). Satellite observations confirm that several glacier systems draining the EAIS have suffered ice mass loss, grounding line retreat, and acceleration of glacial flow (Rignot et al., 2019; Smith et al., 2020).…”

Section: Introductionmentioning

confidence: 99%

“…These observations have inspired new investigations of the vulnerability of the East Antarctic ice shelves to ocean‐driven melt, such as the Shackleton Ice Shelf (SIS)/Denman Glacier System (hereafter referred to as the Shackleton‐Denman System; Figure 1a), an area that is now receiving close attention from the scientific community (Herraiz‐Borreguero & Naveira Garabato, 2022; Urbini et al., 2010; van Wijk et al., 2022). The thinning of the SIS (Paolo et al., 2015) and retreat of the grounding line of the Denman Glacier (Brancato et al., 2020) may indicate an increase in ocean heat transport to the Shackleton‐Denman System.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, the existence of deep channels in the bathymetry over the continental shelf leading to the SIS (see dark blue arrows on Figure 1b and Supporting Information ; Fretwell et al., 2013; McMahon et al., 2023) may facilitate the transport of mCDW to the ice cavity. Therefore, it is critical to determine the vulnerability of the Shackleton‐Denman System to inflows of mCDW (van Wijk et al., 2022).…”

Section: Introductionmentioning

confidence: 99%

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Oceanic Regime Shift to a Warmer Continental Shelf Adjacent to the Shackleton Ice Shelf, East Antarctica

Ribeiro,

Herraiz‐Borreguero,

Rintoul

et al. 2023

JGR Oceans

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The long‐held view that the East Antarctic margin is isolated from warm offshore waters has been challenged by recent observations showing incursions of warm modified Circumpolar Deep Water (mCDW) reaching several East Antarctic ice shelves. However, large areas of the East Antarctic continental shelf remain poorly observed, making it challenging to determine if the supply of oceanic heat to the ice shelves is changing. Here, we use temperature and salinity profiles to the west of the Shackleton Ice Shelf (SIS; ≈100°E) spanning 60 years to assess the variability of the water masses in the context of a changing climate. We document warming and freshening of shelf waters. Prior to 1996, cold mCDW water (θ < −1.6°C) was found below the surface mixed layer and cold Dense Shelf Water (DSW) with a salinity of >34.5 dominated the water column. After 2010, warm mCDW (≥−1.0°C) was widespread over the continental shelf and DSW with salinity over 34.5 was no longer present. The mixing ratio of glacial meltwater indicates that warm mCDW observed in 2011 caused basal melting of the SIS, possibly reducing the salinity of DSW. Increased access of warm waters to the continental shelf may have also occurred on the eastern side of the ice shelf, where glaciological evidence shows the grounding line has retreated. These observations suggest a shift occurred prior to 2011 that has increased the ocean heat supply to the continental shelf and to the SIS, increasing basal melt and reducing DSW formation.

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Vulnerability of Denman Glacier to Ocean Heat Flux Revealed by Profiling Float Observations

Cited by 11 publications

References 40 publications

Sensitivity of simulated water mass transformation on the Antarctic shelf to tides, topography and model resolution

Sensitivity of simulated water mass transformation on the Antarctic shelf to tides, topography and model resolution

Diffusion of Circumpolar Deep Water Towards Antarctica

Oceanic Regime Shift to a Warmer Continental Shelf Adjacent to the Shackleton Ice Shelf, East Antarctica

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