3.8. Pendulum Cove

SITE DESCRIPTION

On February 23, our team recorded two stations at Pendulum Cove. The site is unique because it is located within the collapsed caldera of Deception Island, which affords it significantly more protection from outside elements than the other sites visited (see figure 1 for map of study location). Deception Island is an active volcano, and thus the waters which we observed at Pendulum Cove were affected by the geothermal activity occurring below. At 10:54am, we lowered our conductivity-temperature-depth (CTD) instrument to a depth of 36 meters at the first station. We recorded our second station at 11:15am, during which we lowered the CDT to a depth of 32 meters.

TEMPERATURE

Pendulum Cove 1 can be found along the vertical line to the right whereas Pendulum Cove 2 can be found along the vertical line to the left of the temperature section plot in figure 50. Temperature ranged from 1.96 to 2.22°C at our first station of Pendulum Cove. Temperature decreased constantly with depth at this location.Temperature hardly varied at all at Station 2 of Pendulum Cove. In fact, it seems to have varied no more than 0.05°C (see figure 51).

Figure 50: Temperature gradient observed at Pendulum Cove

Figure 51: Temperature changes over depth in Pendulum Cove (Station 1 red, Station 2 green)

SALINITY

Pendulum Cove 1 is on the right side of the graph whereas Pendulum Cove 2 is on the left side of the graph (see figure 52). Salinity ranged between 33.76 and 33.95 psu in this region. A small pocket of fresher water was observed at the water's surface, most likely formed through the incorporation of melting ice into the top of the water column. Salinity also varied much less in station 2 compared to station 1 at Pendulum Cove, reaching a minimum of 33.87 and a maximum of 33.925 psu.

Station 2 showed a much smaller range of salinity variation than station 1 (see figure 53). This being said, most of the variation found in station 1 is in the top 10 metres of the water column. Below 10 metres, both stations reflected similar results.

Figure 52: Salinity gradient observed at Pendulum Cove

Figure 53: Salinity changes over depth at Pendulum Cove

T-S PLOT

When looking at the potential temperature/saliniy (T/S) plot of Pendulum cove station 1 and 2, we can observe, once again, a negative relationship between potential temperature and salinity (see figure 54 and 55). Potential temperature varies between 1.97 and 2.22°C and salinity varies between 33.76 and 33.945 psu at station 1 (figure 54).

Potential temperature varied between 2.063 and 2.17 °C whereas salinity reflected a range between 33.878 and 33.931 psu at station 2 (see figure 55). The general trend of this relationship is a negative one; colder waters tended to also be more saline whereas warmer waters tended to be less saline.

Figure 54: Potential temperature/salinity plot with isopycnals for Pendulum Cove station 1

Figure 55: Potential temperature/ salinity with isopycnols for Pendulum Cove station 2

DENSITY

Density varied between 16.68 and 16.84 kg/m3 a at station 1 in Pendulum Cove. This represents a very small variation yet it did maintain the regular pattern of increased density as we increase depth in the water column. Density at station 2 of Pendulum Cove was found to vary between 16.68 and 16.84 kg/m3 (see figure 56 and 57).

Over both stations, density did not differ greatly. Station 1 demonstrated slightly more fluctuations in density closer to the surface compared to Station 2. Nevertheless, both stations reflected the common expected pattern of increased density with increased depth in the water column.

Figure 56: Density gradient at Pendulum Cove

*Station 1 is at the right of section whereas station 2 is at the left.

Figure 57: Potential density section plot at Pendulum Cove: potential density changes with depth