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A Warm, Stratified, and Restricted Labrador Sea Across the Middle Eocene and Its Climatic Optimum
Author(s) -
Cramwinckel Marlow J.,
Coxall Helen K.,
Śliwińska Kasia K.,
Polling Marcel,
Harper Dustin T.,
Bijl Peter K.,
Brinkhuis Henk,
Eldrett James S.,
Houben Alexander J. P.,
Peterse Francien,
Schouten Stefan,
Reichart GertJan,
Zachos James C.,
Sluijs Appy
Publication year - 2020
Publication title -
paleoceanography and paleoclimatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.927
H-Index - 127
eISSN - 2572-4525
pISSN - 2572-4517
DOI - 10.1029/2020pa003932
Subject(s) - geology , oceanography , foraminifera , benthic zone , holocene climatic optimum , deep sea , dinoflagellate , bottom water , stratification (seeds) , palynology , ocean current , north atlantic deep water , paleontology , climate change , deep water , seed dormancy , pollen , ecology , botany , germination , dormancy , biology
Several studies indicate that North Atlantic Deep Water (NADW) formation might have initiated during the globally warm Eocene (56–34 Ma). However, constraints on Eocene surface ocean conditions in source regions presently conducive to deep water formation are sparse. Here we test whether ocean conditions of the middle Eocene Labrador Sea might have allowed for deep water formation by applying (organic) geochemical and palynological techniques, on sediments from Ocean Drilling Program (ODP) Site 647. We reconstruct a long‐term sea surface temperature (SST) drop from ~30°C to ~27°C between 41.5 to 38.5 Ma, based on TEX 86 . Superimposed on this trend, we record ~2°C warming in SST associated with the Middle Eocene Climatic Optimum (MECO; ~40 Ma), which is the northernmost MECO record as yet, and another, likely regional, warming phase at ~41.1 Ma, associated with low‐latitude planktic foraminifera and dinoflagellate cyst incursions. Dinoflagellate cyst assemblages together with planktonic foraminiferal stable oxygen isotope ratios overall indicate low surface water salinities and strong stratification. Benthic foraminifer stable carbon and oxygen isotope ratios differ from global deep ocean values by 1–2‰ and 2–4‰, respectively, indicating geographic basin isolation. Our multiproxy reconstructions depict a consistent picture of relatively warm and fresh but also highly variable surface ocean conditions in the middle Eocene Labrador Sea. These conditions were unlikely conducive to deep water formation. This implies either NADW did not yet form during the middle Eocene or it formed in a different source region and subsequently bypassed the southern Labrador Sea.