3.2. Errera Channel

SITE DESCRIPTION

The second zodiac site that we visited was located in the Errera Channel. In total, there were seven stations sampled within the Errera Channel. All sampling occurred in the vicinity of Ronge Island, although no sampling sites were particularly close to the land. The island provided a habitat for both a Gentoo penguin and a Fur seal population. Stations were not in close proximity to the surrounding icebergs and glaciers, but their presence should be noted. At every site, conductivity-temperature-depth (CTD) and Secchi depth measurements were recorded. Most of our Secchi Disk readings were visible to a depth of approximately 6.5 meters. Only two of the measurements were taken while shaded from the sun. However, we noticed no significant difference between the measurements taken in direct sunlight compared to in the shade. The surrounding water was darker than that observed at Brown Bluff, and the turbidity is probably associated with the presence of biological activity in the area. The map (Figure 10) below shows the geographical distribution of the 7 stations. Station 1 was significantly shallower than the rest of the stations. Sampling was conducted from West to East.

Figure 10: The seven sampling sites (stations) within the Errera Channel

TEMPERATURE

In Figure 12, it can be noted that the temperature gradient across the different stations appears to follow the same pattern. Surface water temperatures range from 1°C to 1.5°C, and decrease with depth to an estimated value of 0.7°C. Figure 13 shows an extrapolation of the temperature of the water column across the sampled area. Station 7, which is the furthest away from shore, had the warmest surface water. Surface temperatures decreased as the location got closer to the island. It seems that there was some mixing of ocean water in the area. A possible explanation is that warm surface water carried by wind mixes with colder water that is near the shore. An alternative explanation is that deep-water currents drive colder water to the east.

Figure 11: Stations Legend Figure 12: Station Plot of Temperature

Figure 13: Section Plot of Temperature

SALINITY

Figures 14 and 15 show that salinity decreased with depth at this location. There was a correlation between temperature and salinity in the Errera Channel. The layer of warm water on the right of the graph is the least saline at the area.

Figure 14: Station Plot of Salinity

Figure 15: Section Plot of Salinity

T/S PLOT

The potential temperature/ salinity (T/S) plot (see figure 16) is consistent with respect to the temperature, salinity, and potential density graphs. Warmer water at stations 6 and 7 was less dense, and therefore floated on top of colder and denser water at the bottom. Moreover, the densest water is the deepest water. Overall, findings at the Errera Channel were consistent with the principles of stratification.

Figure 16: Station Plot of Potential Temperature vs Salinity

DENSITY

Density measurements from the Errera Channel were consistent with those of salinity and temperature. The correlation between the figures below (figure 17, figure 18) supports the alternative explanation previously mentioned, namely that deep-water currents likely drive cold water to the east, and thus influence the movement of this ocean water. Colder and denser water is submerged under the incoming warmer water and mixing at depth occurs.

Figure 17: Station Plot of Potential Density

Figure 18: Section Plot of Potential Density

SECCHI DEPTHS

Our Secchi Disk measurements (see table 3) illustrate unique and interesting characteristics of the Errera Channel compared to the other two locations at which we used the Secchi Disk. Although we recorded the most stations of any specific location at the Errera Channel, and did so over a sizable distance, none of the seven stations varied in Secchi Depth by more than 1 meter, ranging between 6 and 7 meters. These findings indicate that the Errera Channel had the highest level of productivity occurring in its photic layer, and this high productivity was consistent across the channel.

Table 3: Secchi Depths