Paleo Slide Set: Heinrich Events: Marine Record of Abrupt Climate Changes in the Late Pleistocene
"Deep-tow fish" being lowered over the end of the ship.

The ocean floor of the North Atlantic covers an area of several hundred thousand square kilometers, 
but a sediment core can extract a cylinder only 7-11 cm in diameter and 2-20 m in length. Because of the enormous 
disparity between the size of the ocean and the size of a core, scientists try to focus coring efforts on sites 
that meet the following two criteria. First of all, sites should be located where they would best exhibit the 
phenomenon that is to be studied. Sediments extracted from shelf margins compared to sediments removed from open 
seas will contain different information about past climates because these sediments were deposited under very 
different environmental conditions. The type of phenomenon scientists are researching thus helps determine where 
they will go to retrieve a core. Once scientists identify a general region of the ocean to study, a decision made 
long before they board ship, they begin to look for sites in the region of the ocean that meet the second important 
criteria: locations where there is the best probability that the core retrieved will provide accurate information. 
High-resolution records of the sea floor and the underlying sediments provided by instruments such as this 
"deep-tow fish", are essential in deciding where cores should be taken. 

Photo Credits:
Anne Jennings 
Institute of Arctic and Alpine Research, University of Colorado-Boulder Boulder, Colorado