Current, Température and Salinity Observations in the
Terra Nova Bay Polynya Area
G.M.R. Manzella1, R. Meloni2 and P. Picco1
’ENEA Marine Environment Research Centre, P.O. Box 316,19100 La Spezia, Italy
2CNR Institute of Physical Oceanography, Forte S. Teresa, 19026 Pozzuolo di
Lerici, La Spezia, Italy
Abstract
Long term (February - December 1995) time sériés of température, salinity and
current hâve been analysed for the understanding of the main dynamics in the
Terra Nova Bay Polynya area. Two main periods hâve been identified on the base
of the observations: 1) from the ice-free sea conditions to the water column density homogénisation, and 2) the winter polynya period. During the first period the
surface fresh water was transformed into High Salinity Shelf Water and sensible
heat was delivered to the polynya surface. An analysis of the current-meter data
during winter time indicated a transport of HSSW from the polynya area to the
Ross Sea of about one Sverdrup.
1 Introduction
y The most characteristic water mass of the Ross Sea is the High Salinity Shelf
Water (HSSW), which is also formed in the Weddell Sea but with a lower salinity
value. This water mass contributes to the formation of Antarctic bottom water
and to a significant amount of shelf water circulating around Antarctica. There
are strong indications that High Salinity Shelf Water is formed in Terra Nova Bay,
where a récurrent polynya has been observed year after year [1].
The two basic mechanisms responsible for polynya formation and maintenance are associated with processes of sensible heat or latent heat [2]. A “sensible heat polynya” is due to vertical convection or upwelling of warm waters driven by winds and/or currents, able to prevent ice formation. The Terra Nova Bay
polynya is believed to belong to type called “latent heat polynya”, whose maintenance mechanism is due to the ice floes driven offshore by strong katabatic
winds [3]. The protection of the Drygalsky Ice Tongue, preventing ice advection
from the south, plays a fundamental rôle in the polynya formation and persistence [4]. Although the dimension of the Terra Nova Bay polynya fluctuâtes in
response to katabatic winds, the presence of an open sea area allows a strong
air-sea interaction, and, as a conséquence, a continuous ice production and
salty shelf water formation.
During February 1995, CTD casts were collected from Terra Nova Bay to Cap
Adare (Fig. 1) and one mooring was deployed in the polynya area (named D in
Terra Nova Bay Polynya Area
G.M.R. Manzella1, R. Meloni2 and P. Picco1
’ENEA Marine Environment Research Centre, P.O. Box 316,19100 La Spezia, Italy
2CNR Institute of Physical Oceanography, Forte S. Teresa, 19026 Pozzuolo di
Lerici, La Spezia, Italy
Abstract
Long term (February - December 1995) time sériés of température, salinity and
current hâve been analysed for the understanding of the main dynamics in the
Terra Nova Bay Polynya area. Two main periods hâve been identified on the base
of the observations: 1) from the ice-free sea conditions to the water column density homogénisation, and 2) the winter polynya period. During the first period the
surface fresh water was transformed into High Salinity Shelf Water and sensible
heat was delivered to the polynya surface. An analysis of the current-meter data
during winter time indicated a transport of HSSW from the polynya area to the
Ross Sea of about one Sverdrup.
1 Introduction
y The most characteristic water mass of the Ross Sea is the High Salinity Shelf
Water (HSSW), which is also formed in the Weddell Sea but with a lower salinity
value. This water mass contributes to the formation of Antarctic bottom water
and to a significant amount of shelf water circulating around Antarctica. There
are strong indications that High Salinity Shelf Water is formed in Terra Nova Bay,
where a récurrent polynya has been observed year after year [1].
The two basic mechanisms responsible for polynya formation and maintenance are associated with processes of sensible heat or latent heat [2]. A “sensible heat polynya” is due to vertical convection or upwelling of warm waters driven by winds and/or currents, able to prevent ice formation. The Terra Nova Bay
polynya is believed to belong to type called “latent heat polynya”, whose maintenance mechanism is due to the ice floes driven offshore by strong katabatic
winds [3]. The protection of the Drygalsky Ice Tongue, preventing ice advection
from the south, plays a fundamental rôle in the polynya formation and persistence [4]. Although the dimension of the Terra Nova Bay polynya fluctuâtes in
response to katabatic winds, the presence of an open sea area allows a strong
air-sea interaction, and, as a conséquence, a continuous ice production and
salty shelf water formation.
During February 1995, CTD casts were collected from Terra Nova Bay to Cap
Adare (Fig. 1) and one mooring was deployed in the polynya area (named D in