TY - JOUR
T1 - Abrupt shoaling of the nutricline in response to massive freshwater flooding at the onset of the last interglacial sapropel event
AU - Grelaud, Michal
AU - Marino, Gianluca
AU - Ziveri, Patrizia
AU - Rohling, Eelco J.
PY - 2012/9/1
Y1 - 2012/9/1
N2 - A detailed assessment of the respective roles of production, export, and subsequent preservation of organic carbon (Corg) in the eastern Mediterranean (EMED) sediments during the formation of sapropels remains elusive. Here we present new micropaleontological results for both surface samples taken at several locations in the EMED and last interglacial sapropel S5 from core LC21 in the southeastern Aegean Sea. A strong exponential anticorrelation between relative abundances of the lower photic zone coccolithophore Florisphaera profunda in the surface sediments and modern concentrations of chlorophyll a (Chl-a) at the sea surface suggests that F. profunda percentages can be used to track past productivity changes in the EMED. Prior to S5 deposition, an abrupt and large increase of F. profunda percentages in LC21 coincided (within the multidecadal resolution of the records) with the marked freshening of EMED surface waters. This suggests a strong coupling between freshwater-bound surface to intermediate water (density) stratification and enhanced upward advection of nutrients to the base of the photic zone, fuelling a productive deep chlorophyll maximum (DCM) underneath a nutrient-starved surface layer. Our findings imply that (at least) at the onset of sapropel formation physical and biogeochemical processes likely operated in tandem, enabling high Corg accumulation at the seafloor.
AB - A detailed assessment of the respective roles of production, export, and subsequent preservation of organic carbon (Corg) in the eastern Mediterranean (EMED) sediments during the formation of sapropels remains elusive. Here we present new micropaleontological results for both surface samples taken at several locations in the EMED and last interglacial sapropel S5 from core LC21 in the southeastern Aegean Sea. A strong exponential anticorrelation between relative abundances of the lower photic zone coccolithophore Florisphaera profunda in the surface sediments and modern concentrations of chlorophyll a (Chl-a) at the sea surface suggests that F. profunda percentages can be used to track past productivity changes in the EMED. Prior to S5 deposition, an abrupt and large increase of F. profunda percentages in LC21 coincided (within the multidecadal resolution of the records) with the marked freshening of EMED surface waters. This suggests a strong coupling between freshwater-bound surface to intermediate water (density) stratification and enhanced upward advection of nutrients to the base of the photic zone, fuelling a productive deep chlorophyll maximum (DCM) underneath a nutrient-starved surface layer. Our findings imply that (at least) at the onset of sapropel formation physical and biogeochemical processes likely operated in tandem, enabling high Corg accumulation at the seafloor.
UR - http://www.scopus.com/inward/record.url?scp=84865410462&partnerID=8YFLogxK
U2 - 10.1029/2012PA002288
DO - 10.1029/2012PA002288
M3 - Article
AN - SCOPUS:84865410462
SN - 2572-4517
VL - 27
JO - Paleoceanography and Paleoclimatology
JF - Paleoceanography and Paleoclimatology
IS - 3
M1 - PA3208
ER -