Open AccessStable carbon isotope patterns of marine biomarker lipids in the Arctic Ocean during Eocene Thermal Maximum 2
Author(s) -
Schoon Petra L.,
Sluijs Appy,
Sinninghe Damsté Jaap S.,
Schouten Stefan
Publication year - 2011
Publication title -
paleoceanography
Language(s) - English
Resource type - Journals
eISSN - 1944-9186
pISSN - 0883-8305
DOI - 10.1029/2010pa002028
Subject(s) - alkenone , oceanography , geology , water column , arctic , isotopes of carbon , paleoceanography , carbon cycle , plankton , anoxic waters , total organic carbon , phytane , paleontology , environmental chemistry , sea surface temperature , ecosystem , chemistry , source rock , ecology , structural basin , biology
The middle Paleocene through early Eocene long‐term gradual warming was superimposed by several transient warming events, such as the Paleocene‐Eocene Thermal Maximum (PETM) and Eocene Thermal Maximum 2 (ETM2). Both events show evidence for extreme global warming associated with a major injection of carbon into the ocean‐atmosphere system, but the mechanisms of carbon injection and many aspects of the environmental response are still poorly understood. In this study, we analyzed the concentration and stable carbon isotopic ( δ 13 C) composition of several sulfur‐bound biomarkers derived from marine photoautotrophs, deposited in the Arctic Ocean at ∼85°N, during ETM2. The presence of sulfur‐bound biomarkers across this event points toward high primary productivity and anoxic bottom water conditions. The previously reported presence of isorenieratene derivatives indicates euxinic conditions in the photic zone, likely caused by a combination of enhanced primary productivity and salinity stratification. The negative carbon isotope excursion measured at the onset of ETM2 for several biomarkers, ranges between 3‰ and 4.5‰, much larger than the ∼1.4‰ recorded in marine carbonates elsewhere, suggesting substantial enhanced isotopic fractionation by the primary producers likely due to a significant rise in p CO 2 . In the absence of biogenic carbonates in the ETM2 section of our core we use coeval planktonic δ 13 C from elsewhere to estimate surface water δ 13 C in the Arctic Ocean and then apply the relation between isotopic fractionation and p CO 2 , originally calibrated for haptophyte alkenones, to three selected organic biomarkers (i.e., S‐bound phytane, C 35 hopane, and a C 25 highly branched isoprenoid). This yields p CO 2 values potentially in the range of four times preindustrial levels. However, these estimates are uncertain because of a lack of knowledge on the importance of p CO 2 on photosynthetic isotopic fractionation.