Marine ice recycling at the southern McMurdo Ice Shelf, Antarctica

Koch, Inka; Fitzsimons, Sean J.; Samyn, Denis; Tison, Jean‐Louis

doi:10.3189/2015jog14j095

Cited by 10 publications

(19 citation statements)

References 77 publications

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“…The smooth band along the marine ice exposure has a similar density, although appearing with an albedo that is indiscernible from the snow-covered part of the ice-shelf on satellite imagery. We interpret this band as marine ice covered by a thin veneer of possibly seasonal and/or wind-blown snow, which is supported by in field ground-based radar and ice sample evidence (Koch, 2016). It can also be shown that the limit of the snow-covered part of SMIS can reach further north on Landsat images and varies seasonally.…”

Section: Marine-to-meteoric Ice Transitionsupporting

confidence: 80%

“…This argument is supported by the known exposure of marine ice at the ice-shelf surface within the adjacent EF1. Such a setting accommodates the ice-shelf vertical structure proposed by Koch (2016) from ground radar observations. In that scenario, the slope break in the basal reflector delimiting SMIS2 from SMIS3 (Fig.…”

Section: Basal Unitsmentioning

confidence: 93%

“…SMIS has a heterogeneous ice composition and is made up of meteoric and marine ice, which is exposed at the surface in its south due to a negative surface ablation (Kellogg and others, 1991; Fitzsimons and others, 2012a; Koch and others, 2015). Since there is a large thickness difference to the adjacent RIS, a steep basal gradient to the much thinner SMIS likely facilitates generation of frazil ice crystals from buoyant supercooled melt water and thus the formation of basal marine ice (Koch, 2016). Due to its large surface gradients in local accumulation (Clifford, 2005; Koch, 2016), SMIS is believed to sustain itself.…”

Section: Contextmentioning

confidence: 99%

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Surface and basal boundary conditions at the Southern McMurdo and Ross Ice Shelves, Antarctica

et al. 2019

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We derive the surface and basal radar reflectance and backscatter coefficients of the southern McMurdo Ice Shelf (SMIS) and part of the nearby Ross Ice Shelf (RIS), Antarctica, from radar statistical reconnaissance using a 60-MHZ airborne survey. The surface coefficients are further inverted in terms of snow density and roughness, providing a spatial distribution of the processes contributing to the surface boundary conditions. We disentangle the basal coefficients from surface transmission losses, and we provide the basal coherent content, an indicator of the boundary geometric disorder that is also self-corrected from englacial attenuation. The basal radar properties exhibit sharp gradients along specific iso-depths, suggesting an abrupt modification of the ice composition and geometric structure. We interpret this behavior as locations where the pressure-melting point is reached, outlining fields of freezing and melting ice. Basal steps are observed at both SMIS and RIS, suggesting a common geometric expression of widespread basal processes. This technique offers a simultaneous view of both the surface and basal boundary conditions to help investigate the ice-shelf stability, while its application to airborne data significantly improves coverage of the difficult-to-observe ice–ocean boundary. It also provides constraints on thermohaline circulation in ice shelves cavities, which are analogs for ice-covered ocean worlds.

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Section: Marine-to-meteoric Ice Transitionsupporting

confidence: 80%

Section: Basal Unitsmentioning

confidence: 93%

Section: Contextmentioning

confidence: 99%

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Surface and basal boundary conditions at the Southern McMurdo and Ross Ice Shelves, Antarctica

et al. 2019

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“…The larger maximum, peak A, likely originates from the confluence of the McMurdo and Ross Ice Shelves (Robinson et al, 2014) as 565 indicated by the arrow north of Black Island in Figure 11. Alternatively, marine ice has been found in the southern McMurdo Ice Shelf (Koch et al, 2015;Grima et al, 2019) and a possible additional source may emerge from the channel between Black Island and the Brown Peninsula (see Figure 1a and 11). Once it emerges from under the ice shelf and spreads out under the fast ice, this stream moves westward under the influence of the Coriolis force (Robinson et al, 2014) as modelled by Cheng et al (2019).…”

Section: Discussionmentioning

confidence: 99%

Airborne mapping of the sub-ice platelet layer under fast ice in McMurdo Sound, Antarctica

Haas¹,

Langhorne²,

Rack³

et al. 2020

Preprint

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Abstract. Basal melting of ice shelves can result in the outflow of supercooled ice shelf water, which can lead to the formation of a sub-ice platelet layer (SIPL) below adjacent sea ice. McMurdo Sound, located in the southern Ross Sea, Antarctica, is well known for the occurrence of a SIPL linked to ice shelf water outflow from under the McMurdo Ice Shelf. Airborne, single frequency, frequency-domain electromagnetic induction (AEM) surveys were performed in November of 2009, 2011, 2013, 2016, and 2017 to map the thickness and spatial distribution of the landfast sea ice and underlying, porous SIPL. We developed a simple method to retrieve the thickness of the consolidated ice and SIPL from the EM inphase and quadrature components, supported by EM forward modeling, and calibrated and validated by drill-hole measurements. Linear regression of EM inphase measurements of apparent SIPL thickness and drill-hole measurements of true SIPL thickness yields a scaling factor of 0.3 to 0.4, and rms error of 0.47 m. EM forward modeling suggests that this corresponds to SIPL conductivities between 900 and 1800 mS/m, with associated SIPL solid fractions between 0.09 and 0.47. The AEM surveys showed the spatial distribution and thickness of the SIPL well, with SIPL thicknesses of up to 8 m near the ice shelf front. They indicate interannual SIPL thickness variability of up to 2 m. In addition, they reveal high-resolution spatial information about the small-scale SIPL thickness variability, and indicate the presence of persistent peaks in SIPL thickness that may be linked to the geometry of the outflow from under the ice shelf.

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“…The AIS is not the only ice shelf with a marine ice layer. Marine ice layers have also been recorded beneath the Filcher‐Ronne, Ross, Hells Gate, Nansen, and southerm McMurdo ice shelves [e.g., Gow , ; Zotikov et al ., 1980; Souchez et al , ; Oerter et al , ; Eicken et al , ; Tison et al , ; Khazendar et al , ; Lambrecht et al , ; Koch et al , ], and suggested beneath the West Ice Shelf [ Warren et al , ]. This list does not preclude marine ice layers in other less studied ice shelves.…”

Section: The Amery Ice Shelf and The Formation Of The Marine Ice Layermentioning

confidence: 99%

Large flux of iron from the Amery Ice Shelf marine ice to Prydz Bay, East Antarctica

et al. 2016

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The Antarctic continental shelf supports a high level of marine primary productivity and is a globally important carbon dioxide (CO2) sink through the photosynthetic fixation of CO2 via the biological pump. Sustaining such high productivity requires a large supply of the essential micronutrient iron (Fe); however, the pathways for Fe delivery to these zones vary spatially and temporally. Our study is the first to report a previously unquantified source of concentrated bioavailable Fe to Antarctic surface waters. We hypothesize that Fe derived from subglacial processes is delivered to euphotic waters through the accretion (Fe storage) and subsequent melting (Fe release) of a marine‐accreted layer of ice at the base of the Amery Ice Shelf (AIS). Using satellite‐derived Chlorophyll‐a data, we show that the soluble Fe supplied by the melting of the marine ice layer is an order of magnitude larger than the required Fe necessary to sustain the large annual phytoplankton bloom in Prydz Bay. Our finding of high concentrations of Fe in AIS marine ice and recent data on increasing rates of ice shelf basal melt in many of Antarctica's ice shelves should encourage further research into glacial and marine sediment transport beneath ice shelves and their sensitivity to current changes in basal melt. Currently, the distribution, volume, and Fe concentration of Antarctic marine ice is poorly constrained. This uncertainty, combined with variable forecasts of increased rates of ice shelf basal melt, limits our ability to predict future Fe supply to Antarctic coastal waters.

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Marine ice recycling at the southern McMurdo Ice Shelf, Antarctica

Cited by 10 publications

References 77 publications

Surface and basal boundary conditions at the Southern McMurdo and Ross Ice Shelves, Antarctica

Surface and basal boundary conditions at the Southern McMurdo and Ross Ice Shelves, Antarctica

Airborne mapping of the sub-ice platelet layer under fast ice in McMurdo Sound, Antarctica

Large flux of iron from the Amery Ice Shelf marine ice to Prydz Bay, East Antarctica

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