NOAA Teacher at Sea
Aboard NOAA Ship Henry B. Bigelow
July 20 — August 1, 2011
Mission: Cetacean and Seabird Abundance Survey
Geographical Area: North Atlantic
Date: July 26, 2011
Air Temp: 20 ºC
Water Temp: 20 ºC
Wind Speed: 3 knots
Water Depth: 4141 meters
Science and Technology Log
To quantify sea conditions, scientists use the Beaufort Scale. Calm waters with no wind is a Beaufort state of zero but when the wind speed increases and white caps start to form the Beaufort state raises to a 4. Good observation conditions for sighting marine mammals fall between sea state 0-3. When the white caps form it gets difficult to distinguish between a white cap and a dolphin splash, decreasing our chances of seeing all the animals in our survey area.
Today, the sighting conditions were good with the sea state varying from a 1-3 over the course of the day. While the conditions were good we did not see any animals for hours. This was surprising to many of the scientists so we looked more closely at the conditions in the water to investigate the lack of sightings.
Three times a day (morning, noon and night) a system of nets with a probe attached is deployed to sample the water under the ship. The net is called a Bongo net, due to its dual net design that looks similar to a Bongo drum. The net is made of a fine mesh that catches small animals swimming below the ship. The probe, attached to the net, is called a CTD, which stands for conductivity, temperature and depth. Scientists can use the combination of the animals found in the net and the readings from the CTD to make conclusions about the productivity of the waters around the ship. The data collected at our noon deployment gave great insight into our lack of visual and acoustic sightings.
During our noon Bongo net deployment an interesting phenomenon was seen in the data. First, the nets that typically collect animals were nearly empty. Secondly, the CTD data showed very little change in water density between the surface and 200m. This lack of change tells scientists that there is very little mixing of the ocean currents in this area of the North Atlantic. Mixing usually causes colder, nutrient rich water to move toward the surface supplying animals with the oxygen and nutrients they need to grow and reproduce quickly. When mixing is absent small animals are not as abundant eliminating the food source for the rest of the food chain. With no food, dolphins and whales move out of the area to more fertile waters. Hopefully, we will move to more productive areas and increase our cetacean sightings.
We have been at sea for 5 days now. I have figured out my routine and I am really enjoying being away from land. Surprisingly for a ship, internet speeds are quick, DirectTV is crystal clear and the laundry facilities are efficient. (It pays to be on one of the newer, technologically advanced ships in NOAA’s fleet. ) The food has been outstanding and I am making some new friends. Getting up early, 5am, may bothersome, but the sunrises and clear air have made the mornings a great part of the day. After dinner the crew has a variety of games to pass the time including ladder golf, bean bag toss and darts. If you think these games are challenging on land, adding the roll of the ship adds a new level of difficulty.