The temperature and salinity fine structure of the ocean under the Ross Ice Shelf

Foster, Theodore D.

doi:10.1029/jc088ic04p02556

Cited by 38 publications

(37 citation statements)

References 26 publications

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“…The fact that Antarctic surface waters are typically free of terrigenous SPM [Elverh6i and Roaldset, 1983;Gieskes et al, 1987] may hide the fact that appreciable transport is occurring along glacial fronts in deep water. Because fine structure has been found to be associated with ice tongues and ice shelves [Jacobs et al, 1981;Jacobs, 1989;Foster, 1983;Foldvik and Gammelsrod, 1988;Potter et al, 1988], it may be that appreciable SPM transport is also a significant, but as yet undocumented, process in these environments as well.…”

Section: Deflection Of Cold Tonguesmentioning

confidence: 98%

Fine structure and suspended sediment transport in three Antarctic fjords

Domack¹,

Williams²

1990

Antarctic Research Series

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As part of a program to investigate modem processes of sedimentation along the Antarctic Peninsula, several glaciated fjords were examined with respect to their physical oceanographic and bottom sediment characteristics. Measurements in the ice proximal (less than 1 km) environment of three fjords show unique characteristics of salinity, temperature, and light transmissivity versus depth. Fine-scale layering (5 to 25 m thick) occurs as relatively cold and turbid water alternates with relatively warm and clear water. The cold, turbid waters are neutrally buoyant, with respect to the ambient water, and are best developed close to glacier termini, at depths of between 100 and 400 m. The data are interpreted as an indication of horizontally flattened tongues or plumes which are generated by tidal-driven circulation, cooling, and ice melting within subglacial marine cavities. Tidal flushing of near-surface crevasses also adds to the complexity of circulation. Significant quantities of suspended sediment (concentrations of up to 7 mg/l) are transported by the horizontal layers into open bays or outer reaches of the fjord system. This represents a new mechanism for the transport of sediment within fjord environments, one which may be characteristic of polar settings. INTRODUCTION Antarctic fjord environments are critical settings with respect to prospects for future development of the Antarctic landmass, yet little is known concerning characteristics of circulation and sedimentation in these heavily glaciated embayments. Because of this, the potential impact of marine pollutants and contamination are difficult to assess. Most studies on fjords recognize the importance of estuarine-type circulation which is driven by fluvial discharge and/or glacial meltwater at the fjord head [Syvitski, 1989]. In these settings, surface outflows of low-salin,:ty, turbid water are important for the dispersal of suspended sediment and, thus, exert a strong control upon resulting facies patterns and the fate of contaminants [Syvitski et al., 1987]. In the absence of significant meltwater input, particularly that which is derived by surface heating and precipitation, other processes could be expected to dominate. However, observaaNow at Department of Geophysics, Stanford University, Stanford, California 94305. tions of such processes are limited by the seasonal bias of field studies and by the traditional emphasis upon deepwater and shelf oceanography in the Antarctic [Jacobs, 1989]. Theoretical considerations, laboratory observations, and limited field observations suggest that winddriven currents, diffusive convection, and tidal pumping may be important aspects of ice proximal circulation within polar fjords (van Heijst [1987], Horne [1985],Josberger and Martin [1981J, Jacobs et al. [1981], MacAyeaf[1985], and others). However, the relative importance of these mechanisms and their role in sediment transport has not been addressed. The results presented in this paper represent some of the first observations made on water characteristics wi...

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Section: Deflection Of Cold Tonguesmentioning

confidence: 98%

Fine structure and suspended sediment transport in three Antarctic fjords

Domack¹,

Williams²

1990

Antarctic Research Series

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“…Over the past decades, monitoring the ocean underneath the Amery Ice Shelf has been an important objective of the Amery Ice Shelf‐Ocean Research (AMISOR) Project. While significant data sets have been collected from beneath ice shelves in West Antarctica [e.g., Clough and Hansen , ; Foster , ; Jacobs et al ., ; Nicholls and Jenkins , ], the AMISOR Project has provided the first comprehensive data set for investigation of ice shelf‐ocean interactions in East Antarctica. The data, collected since 2001 (and ongoing) includes oceanographic moorings in boreholes through the ice shelf and off the ice shelf front (discussed in the present article), sediment cores, glacial and marine ice samples, ocean currents, thermistors, and fiber‐optic ice/ocean temperature measurements, in addition to a wide range of glaciological and geophysical measurements.…”

Section: Introductionmentioning

confidence: 99%

Basal melt, seasonal water mass transformation, ocean current variability, and deep convection processes along the Amery Ice Shelf calving front, East Antarctica

et al. 2016

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Despite the Amery Ice Shelf (AIS) being the third largest ice shelf in Antarctica, the seasonal variability of the physical processes involved in the AIS‐ocean interaction remains undocumented and a robust observational, oceanographic‐based basal melt rate estimate has been lacking. Here we use year‐long time series of water column temperature, salinity, and horizontal velocities measured along the ice shelf front from 2001 to 2002. Our results show strong zonal variations in the distribution of water masses along the ice shelf front: modified Circumpolar Deep Water (mCDW) arrives in the east, while in the west, Ice Shelf Water (ISW) and Dense Shelf Water (DSW) formed in the Mackenzie polynya dominate the water column. Baroclinic eddies, formed during winter deep convection (down to 1100 m), drive the inflow of DSW into the ice shelf cavity. Our net basal melt rate estimate is 57.4 ± 25.3 Gt yr−1 (1 ± 0.4 m yr−1), larger than previous modeling‐based and glaciological‐based estimates, and results from the inflow of DSW (0.52 ± 0.38 Sv; 1 Sv = 106 m3 s−1) and mCDW (0.22 ± 0.06 Sv) into the cavity. Our results highlight the role of the Mackenzie polynya in the seasonal exchange of water masses across the ice shelf front, and the role of the ISW in controlling the formation rate and thermohaline properties of DSW. These two processes directly impact on the ice shelf mass balance, and on the contribution of DSW/ISW to the formation of Antarctic Bottom Water.

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“…Over the past decades, monitoring of the ocean underneath the AIS has been an important objective of the Amery Ice Shelf‐Ocean Research (AMISOR) Project. While significant data sets have been retrieved from beneath ice shelves in West Antarctica [e.g., Clough and Hansen , ; Foster , ; Jacobs et al ., ; Nicholls and Jenkins , ], results from the AMISOR Project (2001–ongoing) comprise a comprehensive array of data (oceanographic moorings, sediment cores, glacial and marine ice samples, ocean currents, thermistors, and fiber‐optic ice/ocean temperature measurements, in addition to a wide range of glaciological and geophysical measurements) for investigating ice shelf‐ocean interactions.…”

Section: Introductionmentioning

confidence: 99%

Circulation of modified Circumpolar Deep Water and basal melt beneath the Amery Ice Shelf, East Antarctica

et al. 2015

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Antarctic ice sheet mass loss has been linked to an increase in oceanic heat supply, which enhances basal melt and thinning of ice shelves. Here we detail the interaction of modified Circumpolar Deep Water (mCDW) with the Amery Ice Shelf, the largest ice shelf in East Antarctica, and provide the first estimates of basal melting due to mCDW. We use subice shelf ocean observations from a borehole site (AM02) situated ∼70 km inshore of the ice shelf front, together with open ocean observations in Prydz Bay. We find that mCDW transport into the cavity is about 0.22 ± 0.06 Sv (1 Sv = 106 m3 s−1). The inflow of mCDW drives a net basal melt rate of up to 2 ± 0.5 m yr−1 during 2001 (23.9 ± 6.52 Gt yr−1 from under about 12,800 km2 of the north‐eastern flank of the ice shelf). The heat content flux by mCDW at AM02 shows high intra‐annual variability (up to 40%). Our results suggest two main modes of subice shelf circulation and basal melt regimes: (1) the “ice pump”/high salinity shelf water circulation, on the western flank and (2) the mCDW meltwater‐driven circulation in conjunction with the “ice pump,” on the eastern flank. These results highlight the sensitivity of the Amery's basal melting to changes in mCDW inflow. Improved understanding of such ice shelf‐ocean interaction is crucial to refining projections of mass loss and associated sea level rise.

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The temperature and salinity fine structure of the ocean under the Ross Ice Shelf

Cited by 38 publications

References 26 publications

Fine structure and suspended sediment transport in three Antarctic fjords

Fine structure and suspended sediment transport in three Antarctic fjords

Basal melt, seasonal water mass transformation, ocean current variability, and deep convection processes along the Amery Ice Shelf calving front, East Antarctica

Circulation of modified Circumpolar Deep Water and basal melt beneath the Amery Ice Shelf, East Antarctica

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