Week 1
6 July 2006

The Transect Trajectory: a sampling in Drake Passage

Introduction: Where is Drake Passage?  Drake Passage is the body of water located between the tip of South America and Antarctica. It is 400 miles wide and is the shortest passage between the continents of South America and Antarctica. (See the map above from Geoscience World).

Question: What is the land mass to the east of the Falkland Island? What country/ies is/are visible?

The transect. Top seal marks our position. Bottom seal marks our destination. Octopus resides on So. Shetland Island.

The passage was named for Sir Frances Drake, who sailed through this region in the 16^th century, while exploring uncharted waters and looting Spanish ships for gold and other treasures. However, Drake never sailed through this passage. He chose to transit the Strait of Magellan from the Atlantic to the Pacific. (More on Drake passage, pirates and privateers in subsequent episodes.)

Extension exercises: Look for maps on the voyages of both Magellan and Drake. Did either of these early explorers visit what is now the continental U.S.? What countries were each of these early explorers from and what was the purpose of their voyages?

Super Science: The Transect Trajectory  

For the next few days, scientists and crew on the Nathaniel B. Palmer will be taking samples on a transect in the Drake Passage. A transect refers to the linear pathway from which samples are collected. For most of this data collection, the ship will remain in motion. Later samplings will be taken while the ship is stopped at predetermined stations.

Types of instruments and measurements:

1. XBTs  are used to measure the temperature and the depth of the ocean from where the sample is taken.. This is a canister like sensor that is launched into the ocean. It relays information back to the ship by means of a copper wire. These instruments are disposable and are not recovered.
   
   
2. XCTDs measure conductivity, temperature, and also the depth where the sample is taken. These measuring devices are also not recovered.
   
   
3. Water sampling is done to identify concentrations of various elements.

Our guide to XBT launching	XBT launcher and canister Link
Rick bravely holds an XBT cannister

One of the reasons scientists are collecting this information is to find out how these conditions and concentrations of elements affect the growth of phytoplankton. There are significant phytoplankton blooms along the edges of the Antarctic continental shelf, especially in summer when there is abundant sunshine. Phytoplankton absorb CO-2.

Extension exercise: How do people affect the amount of CO-2 in the atmosphere? What are the effects of increased amounts of CO-2?

This research is just one of many projects that helps scientists interpret past and current conditions on earth and also helps them make predictions about the future.