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The southern Norwegian Sea during the last 45 ka: hydrographical reorganizations under changing ice‐sheet dynamics
Author(s) -
Wary Melanie,
Eynaud Frederique,
Rossignol Linda,
Zaragosi Sebastien,
Sabine Marjolaine,
Castera MarieHelene,
Billy Isabelle
Publication year - 2017
Publication title -
journal of quaternary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.142
H-Index - 94
eISSN - 1099-1417
pISSN - 0267-8179
DOI - 10.1002/jqs.2965
Subject(s) - geology , stadial , oceanography , north atlantic deep water , deglaciation , ice sheet , glacial period , halocline , holocene , climatology , thermohaline circulation , paleontology , salinity
ABSTRACT The last glacial millennial Heinrich and Dansgaard–Oeschger events have been the subject of many studies in recent decades. However, significant uncertainties remain, notably regarding associated oceanic mechanisms. Here we investigate the evolution of hydrographical conditions in the 3–41 ka cal BP interval of core MD99‐2285 located in the southern Norwegian Sea. Our results reveal an unusual scheme with: (i) warm Greenland interstadials marked by a relatively cold and homogeneous upper water column seasonally ice‐covered and active deep water formation, (ii) cold Greenland and Heinrich stadials marked by a warm, low‐salinity and nearly sea ice‐free surface layer with iceberg calving, separated by a strong halocline from a colder and saltier subsurface layer, as well as strongly reduced deep convection, and (iii) close to modern Holocene oceanic conditions, but showing significant differences from interstadial conditions. Hence, our work strongly suggests different deep‐water convection modes in the Nordic Seas, with, notably, interstadial deep water formation mainly forced by brine release. According to our results, the transition from the glacial mode of deep water formation to the modern open ocean convection mode might have occurred at the end of deglaciation/beginning of the Holocene, when both modes probably occurred.