Antarctic Blog
15 March 2017
Volcanic eruption on the South Sandwich Islands
by Julia Schmale
Position 57°S 32°W
The South Sandwich Islands are just one and a half days of steaming away from South Georgia. We left South Georgia in a storm and were unable to outrun it before getting to the islands. After trawling at the northern end of the Archipelago, we actually stationed downwind of Saunders Island for our project to measure the emissions of seabirds. Unfortunately, the rain and high wind speeds inhibited transport of any plume and so all we could measure were very low particle number concentrations.
Position 57°S 32°W
The South Sandwich Islands are just one and a half days of steaming away from South Georgia. We left South Georgia in a storm and were unable to outrun it before getting to the islands. After trawling at the northern end of the Archipelago, we actually stationed downwind of Saunders Island for our project to measure the emissions of seabirds. Unfortunately, the rain and high wind speeds inhibited transport of any plume and so all we could measure were very low particle number concentrations.
Southern Thule
All day we sailed along the western sides of the islands covered in thick fog to get to the southern end for another round of trawling. By the end of the day, we almost had given up hope of seeing any of the islands. However, just at sunset, the sky cleared up and we could see the Scott and Southern Thule Islands. Their lower parts were covered with penguins. Seals and whales were diving in the vicinity and many seabirds were looking for food. The scene was spectacular in the late day’s light.
As we went sailing on, barely past the islands, we picked up an enhanced signature of particulate sulfate. The concentration of particulate sulfate increases normally when phytoplankton emits dimethyl sulfide which is oxidized to sulfuric acid, or when wind speeds rise and more sea salt is present in the air. The latter is accompanied by higher chloride concentrations equally stemming from the sea salt. This time, the particulate chloride concentration stayed low. At the same time there was also no indication of a phytoplankton bloom. So it was not immediately apparent what the source of the signal was. Speaking to the Russian delegate from the Arctic and Antarctic Research Institute in St. Petersburg, he told us that they just received notice that one of the South Sandwich Islands volcanos had shown increased activity. Checking the air mass movement based on the ETH forecast data for this expedition, pieces came together and it is highly likely that we picked up the trace of a very recent volcanic eruption. More details will be researched once we are back.
As we went sailing on, barely past the islands, we picked up an enhanced signature of particulate sulfate. The concentration of particulate sulfate increases normally when phytoplankton emits dimethyl sulfide which is oxidized to sulfuric acid, or when wind speeds rise and more sea salt is present in the air. The latter is accompanied by higher chloride concentrations equally stemming from the sea salt. This time, the particulate chloride concentration stayed low. At the same time there was also no indication of a phytoplankton bloom. So it was not immediately apparent what the source of the signal was. Speaking to the Russian delegate from the Arctic and Antarctic Research Institute in St. Petersburg, he told us that they just received notice that one of the South Sandwich Islands volcanos had shown increased activity. Checking the air mass movement based on the ETH forecast data for this expedition, pieces came together and it is highly likely that we picked up the trace of a very recent volcanic eruption. More details will be researched once we are back.
A plume of particulate sulfate