3.7. Gerlache Strait

SITE DESCRIPTION

On the morning of February 22, 2011, our ship stopped in the Gerlache Strait. The location was notably cold and windy and the current appeared to be strong, yet not as strong as the waters in the Antarctic Sound (see observations 3.6). We lowered the conductivity-temperature-depth (CTD) instrument into the water at 10:28 AM to a depth of 290 metres. We also lowered a Niskin Bottle into the water at 10:50AM, with the messenger sent down at 10:55AM to cap the bottle. The sample collected from the Niskin Bottle was taken at a depth of 50 metres. The current appeared to be calmer than that observed in the Antarctic Sound, and we thus made an attempt with our Secchi Disk. Yet in the end, the current proved to be too strong to successfully measure a depth reading without damaging our Secchi Disk.

TEMPERATURE

Temperature varied between 0.2 and 1.1°C over 290 metres in Gerlache Strait (see figure 46). These waters were considerably warmer than those recorded in the Antarctic Sound (see figure 42).

Figure 46: Temperature changes through depth in the Gerlache Strait

SALINITY

Salinity was calculated at a minimum value of 33.3 and a maximum value of 34.52 psu in Gerlache Strait . The section plot below (see figure 47) shows a distinct increase in salinity as one goes lower into water column as expected.

Figure 47: Salinity changes through depth in the Gerlache Strait

T-S PLOT

When looking at the potential temperature/salinity (T/S) plot of Gerlache Strait, we can observe a negative relationship between potential temperature and salinity in this area (see figure 48). As potential temperature decreases, salinity increases. This represents the type of trend one would expect at greater depths since higher pressure has lower temperature and higher salinity. Potential temperature varied between 1.05 and 0.2 °C whereas salinity varied between 33.3 and 34.7 psu.

Figure 48: Potential temperature and salinity plot with isopycnols for the Gerlache Strait

DENSITY

Density varied between 16.6 and 17.6kg/m3, thus representing 1psu of variation over 290m of depth (see figure 49). The density gradient was representative of what we would expect; that is that density increases constantly with increasing depth.

Figure 49: Potential density changes through depth in the Gerlache Strait