Open AccessRegional climate variability in the western subtropical North Atlantic during the past two millennia
Author(s) -
Saenger Casey,
Came Rosemarie E.,
Oppo Delia W.,
Keigwin Lloyd D.,
Cohen Anne L.
Publication year - 2011
Publication title -
paleoceanography
Language(s) - English
Resource type - Journals
eISSN - 1944-9186
pISSN - 0883-8305
DOI - 10.1029/2010pa002038
Subject(s) - intertropical convergence zone , geology , oceanography , tropical atlantic , climatology , foraminifera , atlantic equatorial mode , thermohaline circulation , north atlantic deep water , subtropics , sea surface temperature , northern hemisphere , north atlantic oscillation , hydrography , western hemisphere warm pool , atmospheric circulation , precipitation , geography , benthic zone , fishery , meteorology , biology
Western subtropical North Atlantic oceanic and atmospheric circulations connect tropical and subpolar climates. Variations in these circulations can generate regional climate anomalies that are not reflected in Northern Hemisphere averages. Assessing the significance of anthropogenic climate change at regional scales requires proxy records that allow recent trends to be interpreted in the context of long‐term regional variability. We present reconstructions of Gulf Stream sea surface temperature (SST) and hydrographic variability during the past two millennia based on the magnesium/calcium ratio and oxygen isotopic composition of planktic foraminifera preserved in two western subtropical North Atlantic sediment cores. Reconstructed SST suggests low‐frequency variability of ∼1°C during an interval that includes the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). A warm interval near 1250 A.D. is distinct from regional and hemispheric temperature, possibly reflecting regional variations in ocean‐atmosphere heat flux associated with changes in atmospheric circulation (e.g., the North Atlantic Oscillation) or the Atlantic Meridional Overturning Circulation. Seawater δ 18 O, which is marked by a fresher MCA and a more saline LIA, covaries with meridional migrations of the Atlantic Intertropical Convergence Zone. The northward advection of tropical salinity anomalies by mean surface currents provides a plausible mechanism linking Carolina Slope and tropical Atlantic hydrology.