The influence of an Antarctic glacier tongue on near-field ocean circulation and mixing

Abstract

In situ measurements of flow and stratification in the vicinity of the Erebus Glacier Tongue, a 12 km long floating Antarctic glacier, show the significant influence of the glacier. Three ADCPs (75, 300, and 600 kHz) were deployed close (<50 m) to the sidewall of the glacier in order to capture near-field flow distortion. Scalar (temperature and conductivity) and shear microstructure profiling captured small-scale vertical variability. and a background/residual flow ($4-10 cm s 21 ) flowing to the NW. Turbulence was dominated by deeper mixing during spring tide, likely indicative of the role of bathymetric variation which locally forms an obstacle as great as the glacier. During the neap tide, near-surface mixing was as energetic as that seen in the spring tide, suggesting the presence of buoyancy-driven near-surface flows. Estimates of integrated dissipation rate suggest that these floating extensions of the Antarctic ice sheet alter energy budgets through enhanced dissipation, and thus influence coastal near-surface circulation.

&lt;i&gt;Brief Communication&lt;/i&gt; &quot;The 2013 Erebus Glacier Tongue calving event&quot;

“…The eastern side of the sound is generally thought to flow southward (Robinson and Williams, 2012). However, observations close to shore indicate a northward flow suggesting there might be flow separation around Tent Island and so flowing back towards the NW (Leonard et al, 2006;Stevens et al, 2013). Such currents were observed in observations near the EGT tip in 2010 (Stevens et al, 2013).…”

“…2a, b). GPS transects of glacier freeboard from December 2010 indicate that these depressions imply a marked localized thinning of the glacier (Stevens et al, 2013).…”

Estimation of Ice Shelf Melt Rate in the Presence of a Thermohaline Staircase

“…The observed staircase had a statically stable configuration of relatively warm, fresh water overlying cold, salty water, which is not susceptible to diffusive convection but to differential diffusion. Stevens et al (2014) argues that the layers observed beside the Erebus Glacier Tongue might have formed as a result of shear-driven instability, where the shear is caused by flow over nearby bottom topography. There are no similar topographic features near our drilling sites.…”

Turbulent heat transfer as a control of platelet ice growth in supercooled under-ice ocean boundary layers

“…At the mast site, during the measurement period, profiles made with the mobile TIC Mast B indicated that the water column was isothermal to about 40 m. In addition, data described in Stevens et al (2014) from the same campaign support the contention that, to within ±5 mK, the upper 40 m was isothermal. The upper 15 m exhibited temperatures below the pressure-dependent freezing temperature, i.e.…”

“…The general layout of EFC and its location relative to nearby geographic features is described by Stevens et al (2014Stevens et al ( , 2011 and shown in Fig. 2.…”