FN Archimer Export Format PT J TI Structure of the upper water column in the northwest North Atlantic: Modern versus last glacial maximum conditions BT AF DE VERNAL, A HILLAIRE-MARCEL, C PELTIER, WR WEAVER, AJ AS 1:1;2:1;3:2;4:3; FF 1:;2:;3:;4:; C1 Univ Quebec, GEOTOP, Montreal, PQ H3C 3P8, Canada. Univ Toronto, Dept Phys, Toronto, ON M5S 1A1, Canada. Univ Victoria, Sch Earth & Ocean Sci, Victoria, BC V8W 2Y2, Canada. C2 UNIV QUEBEC (UQAM-GEOTOP), CANADA UNIV TORONTO, CANADA UNIV VICTORIA, CANADA IF 3.871 TC 35 UR https://archimer.ifremer.fr/doc/00223/33405/31861.pdf LA English DT Article CR ENCENS-SHEBA (VT 48)/IMAGES IMAGES (VT/50) TIP 2000 IMAGES 1-MD101 IMAGES 3-IPHIS-MD106 IMAGES 4-MD111 IMAGES V LEG 1-MD114 IMAGES V LEG 4-MD114 IMAGES V LEG 5 NAUSICAA-IMAGES 2-MD105 BO Marion Dufresne DE ;Last Glacial Maximum;LGM;North Atlantic;salinity;density;pycnocline AB During the Last Glacial Maximum, the northwestern North Atlantic constituted a major conduit for Labrador and Greenland ice sheet meltwaters. Vertical density gradients in its upper water masses have been reconstructed by combining information from transfer functions based on dinocysts and from oxygen isotope measurements (delta(18)O) in planktonic foraminifera. Transfer functions yield temperature and salinity and thus potential density (sigma(theta)) for the warmest (August) and coldest (February) months in the photic zone. The delta(18)O values in different size fractions of epipelagic (Globigerina bulloides) and mesopelagic (Neogloboquadrina pachyderma left-coiled (Np1)) foraminifera allow us to assess sigma(theta) gradients through the pycnocline between surface and intermediate waters, based on the calibration of a sigma(theta) versus delta(18)O relationship from transfer function reconstructions. The size and density of Np1 shells provide further constraints on these sigma(theta) gradients. The results show the development of a very strong pycnocline during the LGM with a difference of about 3 (summer) to 1.5 (winter) sigma(theta) units between surface and underlying waters. They indicate conditions unfavorable for vertical convection and support the hypothesis of the spreading of a shallow, low-salinity buoyant layer over the northern North Atlantic. This layer depicted a strong E-W gradient, with maximum seasonal contrast and minimum absolute sigma(theta) values westward. PY 2002 PD OCT SO Paleoceanography SN 0883-8305 PU Amer Geophysical Union VL 17 IS 4 UT 000180656400002 DI 10.1029/2001PA000665 ID 33405 ER EF