The intertropical convergence zone is a near-equatorial band of intense rainfall and convection. Over the modern Atlantic Ocean, its annual average position is approximately 5N, and it is associated with low sea surface salinity and high surface temperatures. This average position has varied since the Last Glacial Maximum, in response to changing climate boundary conditions. The nature of this variation is less clear, with suggestions that the intertropical convergence zone migrated north-south away from the colder hemisphere or that it contracted and expanded symmetrically around its present position. Here we use paired Mg/Ca and δ 18 O measurements of planktonic foraminifera for a transect of ocean sediment cores to reconstruct past changes in tropical surface ocean temperature and salinity in the Atlantic Ocean over the past 25,000 years. We show that the low-salinity, high-temperature surface waters associated with the intertropical convergence zone migrated southward of their present position during the Last Glacial Maximum, when the Northern Hemisphere cooled, and northward during the warmer early Holocene, by about ±7of latitude. Our evidence suggests that the intertropical convergence zone moved latitudinally over the ocean, rather than expanding or contracting. We conclude that the marine intertropical convergence zone has migrated significantly away from its present position owing to external climate forcing during the past 25,000 years.
Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964, United States; Department of Environmental Studies, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105, United States; College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, United States; Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02543, United States; NIOZ Royal Netherlands Institute for Sea Research, Department of Marine Geology, Landsdiep 4, 1797 SZ 't Horntje (Texel), Netherlands
Recommended Citation:
Arbuszewski J.A.,Demenocal P.B.,Cléroux C.,et al. Meridional shifts of the Atlantic intertropical convergence zone since the Last Glacial Maximum[J]. Nature Geoscience,2013-01-01,6(11)