Townsend Cromwell
TC-99-05 Swordfish Oceanography
TC-99-05 Swordfish OceanographyApril 26-May 9, 1999
April 29, 1999 It's been a busy week for the TOWNSEND CROMWELL and her crew. We completed our lobster tagging cruise and returned to Honolulu on April 21, having tagged and released 2686 spiny lobsters on Necker Island's reef. In addition, we collected 300 specimens from 60 different species for the Hawaiian Monk Seal Nutrition study and collected data for miscellaneous other studies. Upon arriving, we were greeted by NOAA Operations Fleet Inspectors for the ship's annual Fleet Inspection. These inspectors provide the invaluable service of inspecting NOAA's research vessels for compliance with safety regulations and for making recommendations for safer procedures and equipment. The import was a busy time as the ship was unloaded of lobster traps and reloaded with supplies and equipment for the next cruise. Simultaneously, the NOAA inspectors inspected the ship's equipment, records, operations and procedures. On April 26 we departed the pier to hold drills and perform maneuvers for the inspectors (above right). After which, we transferred the inspectors to shore, embarked the scientists for our present cruise, and departed for waters north of the Hawaiian Islands.
On our present cruise, we are gathering oceanographic data as we travel north along the 158W longitude line (left). Along with information picked up by the ship's sensors (ADCP and TSG), we are performing CTD casts (below right) (short for Conductivity-Temperature-Depth) every 15 nautical miles to depths of 500 meters (1640 feet). The instrument used for CTDs weighs about 1000 lb. and is lowered on a cable by one of our deck winches. As the unit descends and ascends, it collects data on Temperature, Depth, Salinity, Oxygen and Chlorophyll levels. Chlorophyll is used as an indication of the amount of algae (phytoplankton) present in the water. The unit also has numerous large bottles attached to it which are remotely triggered by one of the ship's computers to collect samples of water at various depths for further analysis.
The data collected from this cruise will be used to gain a better understanding of a shifting boundary that forms between two masses of ocean water north of the Hawaiian Islands. Just as the boundary between two masses of air are referred to as a "Front" (I.E. "Warm Front" or "Cold Front"), this oceanographic boundary is referred to as the Subtropical Front. This front is characterized by a sudden shift in salinity and temperature of the sea water and an increase in phytoplankton. It's important commercially as there are a higher numbers of swordfish that tend to be commercially caught near it. We are studying the front in an effort to gain a better understanding of the relationship between the fish and the frontal environment in which they inhabit.Yesterdays cruise write-ups for TC-99-05