Evidence for enhanced convection of North Pacific Intermediate Water to the low‐latitude Pacific under glacial conditions

• Published in: Paleoceanography Vol. 32; no. 1; pp. 41 - 55
• Main Authors: Max, L., Rippert, N., Lembke‐Jene, L., Mackensen, A., Nürnberg, D., Tiedemann, R.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-01-2017
• Subjects: Biogeochemistry; Boundary conditions; Carbon isotopes; Cibicides lobatulus; Composition; Convection; Dynamics; equatorial Pacific; Equatorial regions; Evolution; Foraminifera; Intermediate water; Intermediate water masses; Isotopes; last glacial period; Latitude; Mineral nutrients; North Pacific; Nutrient cycles; Ocean circulation; Ocean currents; Oceanography; stable isotopes; subthermocline; Surface water; Tropical climate; Ventilation; Water depth; Water masses; IN, North Pacific, North Pacific Intermediate Water; IS, Equatorial Pacific; INE, Subarctic Pacific; IS, Tropical Pacific; IN, Bering Sea; IN, North Pacific
• ISSN: 0883-8305; 2572-4517; 1944-9186; 2572-4525
• DOI: 10.1002/2016PA002994

We provide high‐resolution foraminiferal stable carbon isotope (δ13C) records from the subarctic Pacific and Eastern Equatorial Pacific (EEP) to investigate circulation dynamics between the extratropical and tropical North Pacific during the past 60 kyr. We measured the δ13C composition of the epibenthic foraminiferal species Cibicides lobatulus from a shallow sediment core recovered from the western Bering Sea (SO201‐2‐101KL; 58°52.52′N, 170°41.45′E; 630 m water depth) to reconstruct past ventilation changes close to the source region of Glacial North Pacific Intermediate Water (GNPIW). Information regarding glacial changes in the δ13C of subthermocline water masses in the EEP is derived from the deep‐dwelling planktonic foraminifera Globorotaloides hexagonus at ODP Site 1240 (00°01.31′N, 82°27.76′W; 2921 m water depth). Apparent similarities in the long‐term evolution of δ13C between GNPIW, intermediate waters in the eastern tropical North Pacific and subthermocline water masses in the EEP suggest the expansion of relatively 13C‐depleted, nutrient‐enriched, and northern sourced intermediate waters to the equatorial Pacific under glacial conditions. Further, it appears that additional influence of GNPIW to the tropical Pacific is consistent with changes in nutrient distribution and biological productivity in surface waters of the glacial EEP. Our findings highlight potential links between North Pacific mid‐depth circulation changes, nutrient cycling, and biological productivity in the equatorial Pacific under glacial boundary conditions.
Key Points
Expansion of Glacial North Pacific Intermediate Water (GNPIW) to the tropical Pacific
Glacial switch to additional influence of GNPIW at the Eastern Equatorial Pacific
Enhanced GNPIW convection coincides with low‐latitude nutrient and marine productivity changes