3.6. Antarctic Sound

SITE DESCRIPTION

Our ship, the M/V Ushuaia, stopped in the Antarctic Sound on February 20th, 2011 en route to Paradise Bay, and we lowered our CTD into the water at 1:55pm. The current was very strong and did not allow for us to record a Secchi Disk reading, and thus we were only able to take CTD measurements at this location. The weather was sunny with few clouds in the sky and there was a notable wind passing over the Sound. There was a very large iceberg grounded to the sea floor just a few hundred meters from the station where we cast the CDT.

TEMPERATURE

According to our measurements, the water column in the Antarctic Sound was not highly stratified. Temperature only ranged between -0.46 and -0.6 °C over 160 metres (see figure 42). Although there is a small difference between surface waters and waters at 160m depth, this water appears much colder than the majority of our other sites measured.

Figure 42: Temperature changes through depth in Antarctic Sound

SALINITY

Salinity was recorded at a minimum value of 34.27 and a maximum value of 34.46 at our station in the Antarctic Sound (see figure 43). This is a smaller variation in salinity than was found at most other sites. This small difference is most likely due to the gradual increase in density of water through the water column.

Figure 43: Salinity changes through depth in Antarctic Sound

T-S PLOT

Through analysis of the potential temperature/ salinity (T/S) plot taken in the Antarctic Sound, can observe a negative relationship between potential temperature and salinity in this area (see figure 44). As potential temperature decreased, salinity also increased. This reflects the more dense waters being both very cold and very saline whereas warmer waters tended to also be less saline in this region. Warm fresher water on the surface is most likely due to melting ice and heating from solar radiation. This relationship was not constant however; between 34.33 and 34.35 we see a rise in potential temperature that remains unexplained. Overall, potential temperature varied between -0.63 and -0.45°C and salinity ranged between 34.25 and 35.48 psu.

Figure 44: Potential temperature and salinity plot for Antarctic Sound

DENSITY

Density levels were recorded between 16.5 and 17.35kg/m3 (see figure 45). This trend demonstrates the gradual increase in density with increasing depth, as would be expected.

Figure 45: Potential density over depth for Antarctic Sound