ODP Leg 202 abstract

Leg 202 (used to be Leg 201 before 24 August 2000)

SE Paleoceanography

Leg 202 will drill Neogene and older sediments in latitudinal and depth transects of topographic rises in the southeast Pacific (Cocos, Carnegie, Nazca, and Chile Rises). The primary objective is to assess changes in surface intermediate-, deep-, and bottom-water mass interaction between the south Pacific and the Southern Ocean. The subsurface flows, important elements of the global thermohaline circulation, influence the heat, salt, oxygen, and nutrient balances of the whole Pacific Ocean and may trigger global climate feedback associated with heat transport and the carbon cycle. The longitudinal spread of the proposed transects along the Peru-Chile Current will facilitate the study of the northward advection of cold upper-ocean water and upwelling of subsurface water along the eastern boundary. This study will test hypotheses on (1) global thermohaline circulation and the linkage of global oceans through the Antarctic, (2) the interaction of the eastern boundary with equatorial currents and its role in the long-term oceanic carbon dioxode balance, (3) the role of biological productivity on modifying subsurface water masses near the eastern boundary, (4) mechanisms of Southern Hemisphere wind changes (as reflected in boundary current advection) to changing glacial, orbital, and greenhouse gas forcing, and (5) the response of the ocean to the opening and closing of tectonic gateways such as the Drake Passage and the Panama Isthmus and the uplift of the Andes Mountains.

The depth transects in the southeast Pacific will complement those in the western and northern Pacific and will allow assembly of a detailed depth-latitude-time reconstruction of subsurface water masses of the whole Pacific. They will complement existing and planned Atlantic depth transects to form a first-order global view of Neogene evolution of thermohaline circulation. The latitudinal transect will add significant South Pacific data to studies of hemispheric thermal gradients during anomalously warm episodes of Neogene and Paleogene time. They will complement and extend land-based studies of the pole-equator-pole (PEP-1) study of IGBP/PAGES. In addition to addressing goals expressed by JOIDES, these transects are consistent with goals of the MESH Program Plan (MESH, 1994), and the international IMAGES Program Plan (IMAGES, 1994).

Leg Prop # Description Site Prop Lat. Prop Long. Prop Water Depth Prop. Total Depth Prop

202* 465 SE Pacific COC-1B 7°31'N 84°09'W 1000 275

Paleoceanography CAR-1B 0°55'S 81°89'W 1350 480

CAR-2B 1°89'S 82°85'W 2250 500

CAR-3B 4°28'S 85°20'W 3750 300

NAZ-1B 21°33'S 81°43'W 1330 100

NAZ-2B 15°85'S 76°92'W 2700 320

NAZ-3B 16°21'S 76°25'W 3600 230

NAZ-4B 16°70'S 76°11'W 4100 160

CBA-1B 23°60'S 73°60'W 3800 160

CBA-2B 33°40'S 73°72'W 3700 270

CBA-3A 40°14'S 75°45'W 4050 425

CRI-1B 46°50'S 76°30'W 2900 400

CRI-2B 47°10'S 76°35'W 3500 500

CRI-3B 50°70'S 76°90'W 4000 500

CRI-4A 43°47'S 75°93'W 3700 900

*Sites are based on 1995-1996 proposal. Sites will be modified based on recent site survey data, and the number of sites will be reduced to a one leg program.

Staff Scientist: Peter Blum

Operations Schedule | Back to FY 01-02 Abstracts