title: Subtropical Arctic Ocean temperatures during the Palaeocene/Eocene thermal maximum.
abstract: The Palaeocene/Eocene thermal maximum, approximately 55 million years ago, was a brief period of widespread, extreme climatic warming, that was associated with massive atmospheric greenhouse gas input. Although aspects of the resulting environmental changes are well documented at low latitudes, no data were available to quantify simultaneous changes in the Arctic region. Here we identify the Palaeocene/Eocene thermal maximum in a marine sedimentary sequence obtained during the Arctic Coring Expedition. We show that sea surface temperatures near the North Pole increased from 18 degrees C to over 23 degrees C during this event. Such warm values imply the absence of ice and thus exclude the influence of ice-albedo feedbacks on this Arctic warming. At the same time, sea level rose while anoxic and euxinic conditions developed in the ocean's bottom waters and photic zone, respectively. Increasing temperature and sea level match expectations based on palaeoclimate model simulations, but the absolute polar temperatures that we derive before, during and after the event are more than 10 degrees C warmer than those model-predicted. This suggests that higher-than-modern greenhouse gas concentrations must have operated in conjunction with other feedback mechanisms--perhaps polar stratospheric clouds or hurricane-induced ocean mixing--to amplify early Palaeogene polar temperatures.
authors.affiliation: Palaeoecology, Institute of Environmental Biology, Utrecht University, Laboratory of Palaeobotany and Palynology, Budapestlaan 4, 3584 CD Utrecht, The Netherlands. a.sluijs@bio.uu.nl
authors.forename: Appy
authors.initials: A
authors.lastname: Sluijs
authors.forename: Stefan
authors.initials: S
authors.lastname: Schouten
authors.forename: Mark
authors.initials: M
authors.lastname: Pagani
authors.forename: Martijn
authors.initials: M
authors.lastname: Woltering
authors.forename: Henk
authors.initials: H
authors.lastname: Brinkhuis
authors.forename: Jaap S
authors.initials: JS
authors.lastname: Sinninghe Damsté
authors.forename: Gerald R
authors.initials: GR
authors.lastname: Dickens
authors.forename: Matthew
authors.initials: M
authors.lastname: Huber
authors.forename: Gert-Jan
authors.initials: GJ
authors.lastname: Reichart
authors.forename: Ruediger
authors.initials: R
authors.lastname: Stein
authors.forename: Jens
authors.initials: J
authors.lastname: Matthiessen
authors.forename: Lucas J
authors.initials: LJ
authors.lastname: Lourens
authors.forename: Nikolai
authors.initials: N
authors.lastname: Pedentchouk
authors.forename: Jan
authors.initials: J
authors.lastname: Backman
authors.forename: Kathryn
authors.initials: K
authors.lastname: Moran
mesh_terms: D000818:Animals; D001110:Arctic Regions; D004141:Dinoflagellida / Q000302:isolation & purification; D005580:Fossils; D019015:Geologic Sediments / Q000032:analysis / Q000737:chemistry; D017752:Greenhouse Effect; D049690:History, Ancient; D007053:Ice; D009792:Oceans and Seas; D012623:Seawater; D013170:Spores / Q000302:isolation & purification; D013696:Temperature; D013997:Time Factors; D014329:Tropical Climate
chemical_list: D007053:Ice