The closing of a seaway; ocean water masses and global climate change

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doi: 10.1016/S0012-821X(03)00164-X
Author(s): Lear, Caroline H.; Rosenthal, Yair; Wright, James D.
Author Affiliation(s): Primary:
Rutgers University, Institute of Marine and Coastal Sciences, New Brunswick, NJ, United States
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, 210(3-4), p.425-436. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. 43 refs.; illus., incl. 1 table
Summary: The Late Neogene witnessed various major paleoceanographic changes that culminated in intense Northern Hemisphere Glaciation (NHG). The cause and effects of these changes are still debated. We use a multiproxy approach to determine the relative timing of the closure of the Panama gateway, changes in Atlantic circulation, global cooling and ice sheet growth. Benthic foraminiferal Mg/Ca records from a Pacific and an Atlantic Site have been produced and are interpreted in terms of bottom water temperatures. These Mg-temperature records are combined with published benthic δ13C, δ18O and erosion records to reconstruct the flow of proto-North Atlantic Deep Water (proto-NADW) over the past 12 Ma. The results suggest that between 12.5 and 10.5 Ma, and again between about 8.5 and 6 Ma, a nutrient-depleted water mass that was colder (by 1-2°C) and fresher than the intervening deep water mass filled the Atlantic basin. This proto-NADW became warmer (by ∼1°C) and saltier between 6 and 5 Ma, coincident with the restriction of surface water flow through the Central American Seaway. The Mg-temperature records define a subsequent global cooling trend of ∼3.5°C between 5 Ma and today. Early NHG in the late Miocene was perhaps related to the formation of the relatively cold, fresh proto-NADW. The formation of the warmer and saltier proto-NADW in the early Pliocene may have initially limited Northern Hemisphere ice growth. However, the increased moisture released at high northern latitudes associated with formation of "warm" proto-NADW, coupled with the global temperature decrease of deep (and hence polar surface) waters, likely helped initiate the intense NHG of the Plio-Pleistocene. Abstract Copyright (2003) Elsevier, B.V.
Year of Publication: 2003
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Alkaline earth metals; Atlantic Ocean; Benthic taxa; Calcium; Cenozoic; Chemical ratios; Climate change; Cooling; DSDP Site 289; DSDP Site 563; DSDP Site 608; Deep Sea Drilling Project; Equatorial Atlantic; Equatorial Pacific; Foraminifera; Gateways; Geochemistry; Glacial geology; Glaciation; Global change; IPOD; Ice sheets; Invertebrata; Leg 130; Leg 154; Leg 30; Leg 82; Leg 94; Magnesium; Metals; Microfossils; Neogene; North Atlantic; North Atlantic Deep Water; ODP Site 806; ODP Site 926; Ocean Drilling Program; Ocean circulation; Pacific Ocean; Paleo-oceanography; Paleocirculation; Pliocene; Protista; Quaternary; Tertiary; Upper Neogene
Coordinates: S002956 S002955 E1583042 E1583041
N333831 N333832 W0434602 W0434603
N425012 N425013 W0230515 W0230515
N001906 N001907 E1592142 E1592140
N034309 N034309 W0425430 W0425430
Record ID: 2003050838
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands