Modeling modified Circumpolar Deep Water intrusions onto the Prydz Bay continental shelf, East Antarctica

Abstract

An eddy‐resolving coupled regional ocean‐sea ice‐ice shelf model is employed to locate the hot spots where modified Circumpolar Deep Water (mCDW) intrudes onto the continental shelf within Prydz Bay, and locate the paths through which mCDW is transported to the Amery Ice Shelf (AIS) calving front. Evaluation of the model output is with satellite, hydrographic and borehole data. Two critical windows responsible for mCDW intrusions are identified. The first is the eastern branch of the cyclonic Prydz Bay gyre (PBG) that carries mCDW to the ice front line, accounting for an annual mean heat transport of ∼8.7 ×1011 J s−1. The second is located to the east of the Four Ladies Bank (FLB) where mCDW is channeled through submarine troughs, accounting for an annual mean heat transport of ∼16.2 ×1011 J s−1. The eddy‐induced heat transport accounts for ∼23% in the path of the PBG and ∼52% in the path of the eastern coastal current, with respect to their total onshore heat transport. The seasonal pulsing of mCDW intrusions is greatly dependent on the seasonal cycle of the Antarctic Slope Current (ASC) that peaks with a maximum of ∼29.3 Sv at 75°E in June. In austral winter, mCDW is allowed to access the eastern flank of the AIS calving front with potential consequences for the basal mass balance of the AIS. The dynamic effects of small‐scale troughs on the longshore ASC play an important role in the onshore mCDW transport.

On the Modified Circumpolar Deep Water Upwelling Over the Four Ladies Bank in Prydz Bay, East Antarctica

“…To our knowledge, so far, there are only two high-resolution ocean-ice shelf coupled modeling studies that focused on Prydz Bay (Galton-Fenzi et al, 2012;Liu et al, 2017). These two modeling studies were based on RTopo-1.…”

“…The Massachusetts Institute of Technology General Circulation Model coupled with a sea ice model and an ice shelf model was employed in this study (Losch et al, 2010;Marshall et al, 1997;Zhang & Hibler, 1997). The initial conditions were obtained from a previous version, and the parameter settings are the same as those employed in Liu et al (2017). The Japanese 25-year Re-Analysis was used to force the ocean and the sea ice components every 6 hr from 1979.…”

“…Previous simulations with low spatial resolution have provided insights into the oceanic processes within the bay (Galton-Fenzi et al, 2012) and the sub-ice-shelf cavity (Galton-Fenzi et al, 2012; M. J. M. Williams et al, 2001Williams et al, , 2002, but they were mostly limited by the spatial resolution (M. J. M. Williams et al, 2001Williams et al, , 2002 and the representation of the alongshore Antarctic Slope Current (ASC) (Galton-Fenzi et al, 2012). Indeed, the dynamic effects of topography on the ASC that can result in onshore flows have already been clarified in previous studies (Klinck & Dinniman, 2010;Liu et al, 2017;St-Laurent et al, 2013;Thompson et al, 2014). Hence, without the high-accuracy topography and the finer resolution, mCDW intrusion may not be fully captured in previous modeling studies.…”

“…Hence, without the high-accuracy topography and the finer resolution, mCDW intrusion may not be fully captured in previous modeling studies. Based on a high-resolution model, Liu et al (2017) highlighted the important role of troughs to the east of the FLB in mCDW intrusion, yet how mCDW is upwelled onto the western flank of the FLB was not clearly documented. By introducing the latest high-accuracy bathymetry data set, we aim to reproduce the pathways for the mCDW upwelling over the FLB in simulation and so make an original explanation of why mCDW tends to flood the shallow FLB rather than be channeled through the deep PC.…”

“…The topography data set employed in the simulation is the latest topography dataset RTopo-2 (the Refined Topography data set; Schaffer et al, 2016). RTopo-2 could capture topographic features more accurately than RTopo-1 (Timmermann et al, 2010) that was used in Galton-Fenzi et al (2012) and Liu et al (2017).…”