Wintertime Expansion and Contraction of the Terra Nova Bay Polynya
147
then used to describe the character of wintertime ice production and water mass
modification in Terra Nova Bay. Terra Nova Bay was selected as the site for this
study because an extensive meteorological data set exists with which to test this
relationship, and because the winds are persistently strong and offshore with a
high degree of directional constancy, thus making a comparison with a onedimensional polynya model practical.
2 Environmental Conditions at Terra Nova Bay
2.1 Weather Conditions
Terra Nova Bay occupies an area of approximately 6000 km2 (65 km north/south
by 92 km east/west) [ 11 ] in the western Ross Sea near 75°S, 164°E (Fig. 1 ). It is bordered on the south by the floating Drygalski Ice Tongue, on the north by Cape
Washington, and on the west by the Nansen Ice Shelf, which is fed by the Reeves
and Priestley Glaciers.
An autonomous weather station (AWS) was installed on February 6, 1984, on
Inexpressible Island (74.92°S, 163.60°E) along the western shore of Terra Nova
Bay (Fig. 1) [12,13] and has operated intermittently since that time. Air température and vector winds at 1.5 m above the surface and atmospheric pressure at
~l-m height are measured at 10-min intervals and broadcast via the Service
ARGOS Data Collection System to the NOAA polar orbiting meteorolgical satellites [14,15]. In many years, equipment failure during the winter months due to
extreme wind events produced significant gaps in the data record. Nonetheless,
this station has been the only significant source of detailed wintertime meteorological measurements from the région. When two satellites are on orbit, nearly a
continuous sequence of 10-min observations can be collected. Once collected,
the 10-min data are scanned to pick out the nearest observation within ±1 h of
00,03, 06, 09, 12, 15, 18, and 21 h to produce the 3-hourly data set. Occasionally,
due to the particular orbit geometry of the satellites, gaps of several hours, duration do occur in the data record. However, this situation occurred generally less
than 3% of the time. These small gaps were filled with linearly interpolated values using the adjacent good points.
Bromwich [16] reports on the AWS data for the months of February, March,
and April during 1984, 1985, and 1987; there were no data for 1986. Bromwich et
al. [17] describe the 1988 and 1989 katabatic wind régime at Terra Nova Bay using
data from an extended AWS network. Here we focus on data from Inexpressible
Island for the years 1988,1989, and 1990, which correspond to the years when the
Defense Meteorological Satellite Program (DMSP) satellite, F-8, was on orbit.
Aside from the period February 17 - April 4,1990, when wind speed and direction
data are not available [18], the AWS data records are complété (Fig. 2).
Table 1 summarizes monthly mean air températures and standard déviations,
monthly mean wind speed and ±34 percentile limits, and monthly médian wind
direction and directional consistency (defîned as the ratio of the magnitude of the
vector-averaged wind speed to the mean wind speed) based on the 3-hourly meteorological observations. Of particular interest to this study is the directional con-
147
then used to describe the character of wintertime ice production and water mass
modification in Terra Nova Bay. Terra Nova Bay was selected as the site for this
study because an extensive meteorological data set exists with which to test this
relationship, and because the winds are persistently strong and offshore with a
high degree of directional constancy, thus making a comparison with a onedimensional polynya model practical.
2 Environmental Conditions at Terra Nova Bay
2.1 Weather Conditions
Terra Nova Bay occupies an area of approximately 6000 km2 (65 km north/south
by 92 km east/west) [ 11 ] in the western Ross Sea near 75°S, 164°E (Fig. 1 ). It is bordered on the south by the floating Drygalski Ice Tongue, on the north by Cape
Washington, and on the west by the Nansen Ice Shelf, which is fed by the Reeves
and Priestley Glaciers.
An autonomous weather station (AWS) was installed on February 6, 1984, on
Inexpressible Island (74.92°S, 163.60°E) along the western shore of Terra Nova
Bay (Fig. 1) [12,13] and has operated intermittently since that time. Air température and vector winds at 1.5 m above the surface and atmospheric pressure at
~l-m height are measured at 10-min intervals and broadcast via the Service
ARGOS Data Collection System to the NOAA polar orbiting meteorolgical satellites [14,15]. In many years, equipment failure during the winter months due to
extreme wind events produced significant gaps in the data record. Nonetheless,
this station has been the only significant source of detailed wintertime meteorological measurements from the région. When two satellites are on orbit, nearly a
continuous sequence of 10-min observations can be collected. Once collected,
the 10-min data are scanned to pick out the nearest observation within ±1 h of
00,03, 06, 09, 12, 15, 18, and 21 h to produce the 3-hourly data set. Occasionally,
due to the particular orbit geometry of the satellites, gaps of several hours, duration do occur in the data record. However, this situation occurred generally less
than 3% of the time. These small gaps were filled with linearly interpolated values using the adjacent good points.
Bromwich [16] reports on the AWS data for the months of February, March,
and April during 1984, 1985, and 1987; there were no data for 1986. Bromwich et
al. [17] describe the 1988 and 1989 katabatic wind régime at Terra Nova Bay using
data from an extended AWS network. Here we focus on data from Inexpressible
Island for the years 1988,1989, and 1990, which correspond to the years when the
Defense Meteorological Satellite Program (DMSP) satellite, F-8, was on orbit.
Aside from the period February 17 - April 4,1990, when wind speed and direction
data are not available [18], the AWS data records are complété (Fig. 2).
Table 1 summarizes monthly mean air températures and standard déviations,
monthly mean wind speed and ±34 percentile limits, and monthly médian wind
direction and directional consistency (defîned as the ratio of the magnitude of the
vector-averaged wind speed to the mean wind speed) based on the 3-hourly meteorological observations. Of particular interest to this study is the directional con-