An investigation of thermohaline circulation in Terra Nova Bay polynya

Abstract

This paper addresses the study of the thermohaline circulation and convective processes induced by the presence of a coastal polynya in Terra Nova Bay (Ross Sea, Antarctica). These processes are analysed by means of oceanographic observations and numerical simulations. Time series of hydrological parameters and currents show the High Salinity Shelf Water (HSSW) formation with the mixing of the water column down to great depths, and a seasonal cycle of kinetic energy. A two-dimensional time dependent model for the numerical simulation of the effects of polynya on the circulation has been implemented. This model allows estimation of the contribution of thermohaline forcing on the circulation pattern, the amount of ice production consistent with the observed salinity distribution and annual cycle of currents and the amount of HSSW exported. The thermohaline forcing due to the polynya is able to induce strong horizontal currents up to 40 cm s−1 near the polynya area, as well as vertical movements of the order of 1 cm s−1. An annual ice production, ranging from 45 m to 90 m, mixes the water column at great depths, up to 750 m, and increases the salinity of the surface incoming waters up to 34.82. The estimated net north-eastward transport of HSSW ranges from 0.34 Sv to 1.23 Sv, depending on ice production.

Freezing resistance of antifreeze-deficient larval Antarctic fish

“…The surface seawater in the Ross Sea is likely to remain at its FP for approximately 4 months after the hatching of G. acuticeps, and perhaps as much as 2 months after the hatching of both P. antarcticum and P. borchgrevinki. Simultaneous temperature logging at other locations in McMurdo Sound (P. A. Cziko, A. L. DeVries et al, unpublished data) as well as in Terra Nova Bay (Buffoni et al, 2002) reveal nearly identical annual temperature records, with variation primarily in the extent of the warming events. The annual maximum temperatures were between 0.5°C and -1.7°C at all locations in this study during the observation period.…”

“…The seawater in these areas is commonly at its freezing point (FP, -1.91°C), with only rare excursions above -1.0°C (Buffoni et al, 2002;Hunt et al, 2003), and the top 10-30·m of the water column in McMurdo Sound is often slightly supercooled (Hunt et al, 2003;Lewis and Perkin, 1985). Consequently, ice growth is observed on the underside of the sea ice, on fishing lines, and on the sea floor to these depths between September and January (Dayton, 1989;Dayton et al, 1969;Hunt et al, 2003), indicating the presence of minute ice crystals in the water column (Littlepage, 1965).…”

The Evident Role of Clouds on Phytoplankton Abundance in Antarctic Coastal Polynyas

“…They are clearly associated with the complex ocean and atmosphere processes, such as the ocean to atmosphere heat fluxes (Minnett and Key 2007), CO 2 exchange (Sweeney et al 2000), the carbon cycle (Becquevort and Smith 2001), the ocean circulation (Buffoni et al 2002), biological carbon pump, and high primary production (PP) (Arrigo and van Dijken 2003;Lee et al 2012).…”

The penetrative mixing in the Laptev Sea coastal polynya pycnocline layer

“…Julien et al, 1996;Buffoni et al, 2002) examples of convective entrainment are known. For instance, similar to our findings, Melling (2001) reported abrupt decreases in salinity accompanied with drops in temperature to the freezing point, attributing them to the penetrative convection within the North Water polynya.…”