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Abstract. The early Eocene (56 to 48 million years ago) is inferred to havebeen the most recent time that Earth's atmospheric CO2 concentrationsexceeded 1000 ppm. Global mean temperatures were also substantially warmerthan those of the present day. As such, the study of early Eocene climate provides insightinto how a super-warm Earth system behaves and offers an opportunity toevaluate climate models under conditions of high greenhouse gas forcing. TheDeep Time Model Intercomparison Project (DeepMIP) is a systematicmodel–model and model–data intercomparison of three early Paleogene timeslices: latest Paleocene, Paleocene–Eocene thermal maximum (PETM) and earlyEocene climatic optimum (EECO). A previous article outlined the modelexperimental design for climate model simulations. In this article, weoutline the methodologies to be used for the compilation and analysis ofclimate proxy data, primarily proxies for temperature and CO2. Thispaper establishes the protocols for a concerted and coordinated effort tocompile the climate proxy records across a wide geographic range. Theresulting climate “atlas” will be used to constrain and evaluate climatemodels for the three selected time intervals and provide insights into themechanisms that control these warm climate states. We provide version 0.1 ofthis database, in anticipation that this will be expanded in subsequentpublications.

Author(s): James C. Zachos [1]; Gerald R. Dickens [2]; Richard E. Zeebe [3] By the year 2400, it is predicted that humans will have released about 5,000 gigatonnes of carbon [...]

Author(s): Appy Sluijs (corresponding author) [1]; Henk Brinkhuis [1]; Stefan Schouten [3]; Steven M. Bohaty [4]; Cédric M. John [4, 6]; James C. Zachos [4]; Gert-Jan Reichart [2]; Jaap S. [...]

The Paleocene-Eocene thermal maximum (PETM) ca. 55.5 Ma was a geologically brief interval characterized by massive influx of isotopically light carbon, extreme changes in global climate, and profound variations in Earth system processes. An outstanding issue is whether it was an isolated event, or the most prominent example of a recurring phenomenon. Recent studies of condensed deep-sea sections support the latter, but this finding remains uncertain. Here we present and discuss lithologic and carbon isotope records across two lower Eocene outcrops on South Island, New Zealand. The PETM manifests as a marl-rich horizon with a significant negative carbon isotope excursion (CIE). Above, in sediment deposited between 54 and 53 Ma, are four horizons with similar though less pronounced expressions. Marl beds of all five horizons represent increased terrigenous sedimentation, presumably linked to an accelerated hydrological cycle. Five corresponding clay-rich horizons and CIEs are found in deep-sea records, although the lithologic variations represent carbonate dissolution rather than siliciclastic dilution. The presence of five intervals with similar systemic responses in different environments suggests a mechanism that repeatedly injected large masses of [sup.13]C-depleted carbon during the early Eocene. Keywords: Paleocene-Eocene thermal maximum, PETM, carbon isotope excursion, CIE.

Author(s): Mark Pagani (corresponding author) [1, 7]; Nikolai Pedentchouk [1, 7]; Matthew Huber [2, 7]; Appy Sluijs [3]; Stefan Schouten [4]; Henk Brinkhuis [3]; Jaap S. Sinninghe Damsté [4, 5]; [...]

The history of the Arctic Ocean during the Cenozoic era (0-65 million years ago) is largely unknown from direct evidence. Here we present a Cenozoic palaeoceanographic record constructed from >400 m of sediment core from a recent drilling expedition to the Lomonosov ridge in the Arctic Ocean. Our record shows a palaeoenvironmental transition from a warm 'greenhouse' world, during the late Palaeocene and early Eocene epochs, to a colder 'icehouse' world influenced by sea ice and icebergs from the middle Eocene epoch to the present. For the most recent ~14 Myr, we find sedimentation rates of 1-2 cm per thousand years, in stark contrast to the substantially lower rates proposed in earlier studies; this record of the Neogene reveals cooling of the Arctic that was synchronous with the expansion of Greenland ice (~3.2 Myr ago) and East Antarctic ice (~14 Myr ago). We find evidence for the first occurrence of ice-rafted debris in the middle Eocene epoch (~45 Myr ago), some 35 Myr earlier than previously thought; fresh surface waters were present at ~49 Myr ago, before the onset of ice-rafted debris. Also, the temperatures of surface waters during the Palaeocene/Eocene thermal maximum (~55 Myr ago) appear to have been substantially warmer than previously estimated. The revised timing of the earliest Arctic cooling events coincides with those from Antarctica, supporting arguments for bipolar symmetry in climate change. The Cenozoic Arctic Ocean Little was known about the environmental history of the Arctic Ocean before the 2004 ACEX ocean drilling expedition. Now a 430-metre sea floor sediment core has been recovered and its analysis, reported this week, provides a 56-million-year climate record spanning the transition from a warm 'greenhouse' to a colder 'icehouse' world. Several key events are identified during the Cenozoic: surface waters during the Palaeocene/Eocene thermal maximum (55 million years ago) were much warmer than previous estimates; surface-water freshening confirms an intensified hydrological cycle about 49 million years ago; and the first ice-rafted debris occurred 45 million years ago, 35 million years earlier than was thought. The revised timings for the earliest Arctic cooling events coincide with those for Antarctica, supporting suggestions that global climate changed symmetrically about the poles. Analysis of Arctic Ocean sediment core spanning more than 50 million years identifies several key features of Arctic climate history -- the revised timing of the earliest Arctic cooling events implied by this record coincides with those from Antarctica, supporting arguments that climate change is symmetric about the Earth's polar regions., Author(s): Kathryn Moran [sup.1] [sup.31] , Jan Backman [sup.2] , Henk Brinkhuis [sup.3] , Steven C. Clemens [sup.4] , Thomas Cronin [sup.5] , Gerald R. Dickens [sup.6] , Frédérique Eynaud [...]

The Cenozoic Arctic Ocean Little was known about the environmental history of the Arctic Ocean before the 2004 ACEX ocean drilling expedition. Now a 430-metre sea floor sediment core has been recovered and its analysis, reported this week, provides a 56-million-year climate record spanning the transition from a warm 'greenhouse' to a colder 'icehouse' world. Several key events are identified during the Cenozoic: surface waters during the Palaeocene/Eocene thermal maximum (55 million years ago) were much warmer than previous estimates; surface-water freshening confirms an intensified hydrological cycle about 49 million years ago; and the first ice-rafted debris occurred 45 million years ago, 35 million years earlier than was thought. The revised timings for the earliest Arctic cooling events coincide with those for Antarctica, supporting suggestions that global climate changed symmetrically about the poles. A core of sediments taken from underneath the Arctic Ocean provides evidence that ocean conditions could support a free-floating fern, Azolla, during the middle Eocene epoch, roughly 50 million years ago. It has been suggested, on the basis of modern hydrology and fully coupled palaeoclimate simulations, that the warm greenhouse conditions.sup.1 that characterized the early Palaeogene period (55-45 Myr ago) probably induced an intensified hydrological cycle.sup.2 with precipitation exceeding evaporation at high latitudes.sup.3. Little field evidence, however, has been available to constrain oceanic conditions in the Arctic during this period. Here we analyse Palaeogene sediments obtained during the Arctic Coring Expedition, showing that large quantities of the free-floating fern Azolla grew and reproduced in the Arctic Ocean by the onset of the middle Eocene epoch (~50 Myr ago). The Azolla and accompanying abundant freshwater organic and siliceous microfossils indicate an episodic freshening of Arctic surface waters during an ~800,000-year interval. The abundant remains of Azolla that characterize basal middle Eocene marine deposits of all Nordic seas.sup.4,5,6,7 probably represent transported assemblages resulting from freshwater spills from the Arctic Ocean that reached as far south as the North Sea.sup.8. The termination of the Azolla phase in the Arctic coincides with a local sea surface temperature rise from ~10 °C to 13 °C, pointing to simultaneous increases in salt and heat supply owing to the influx of waters from adjacent oceans. We suggest that onset and termination of the Azolla phase depended on the degree of oceanic exchange between Arctic Ocean and adjacent seas., Author(s): Henk Brinkhuis [sup.1] , Stefan Schouten [sup.2] , Margaret E. Collinson [sup.3] , Appy Sluijs [sup.1] , Jaap S. Sinninghe Damsté [sup.2] [sup.4] , Gerald R. Dickens [sup.5] , [...]

The Cenozoic Arctic Ocean Little was known about the environmental history of the Arctic Ocean before the 2004 ACEX ocean drilling expedition. Now a 430-metre sea floor sediment core has been recovered and its analysis, reported this week, provides a 56-million-year climate record spanning the transition from a warm 'greenhouse' to a colder 'icehouse' world. Several key events are identified during the Cenozoic: surface waters during the Palaeocene/Eocene thermal maximum (55 million years ago) were much warmer than previous estimates; surface-water freshening confirms an intensified hydrological cycle about 49 million years ago; and the first ice-rafted debris occurred 45 million years ago, 35 million years earlier than was thought. The revised timings for the earliest Arctic cooling events coincide with those for Antarctica, supporting suggestions that global climate changed symmetrically about the poles. Identification of the Palaeocene/Eocene thermal maximum in a marine sedimentary sequence shows that sea surface temperatures near the North Pole increased from roughly 18 degrees Celsius to over 23 degrees Celsius -- such warm values imply the absence of ice and thus exclude the influence of ice-albedo feedbacks on this Arctic warming. The Palaeocene/Eocene thermal maximum, ~55 million years ago, was a brief period of widespread, extreme climatic warming.sup.1,2,3, that was associated with massive atmospheric greenhouse gas input.sup.4. 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.sup.5. We show that sea surface temperatures near the North Pole increased from ~18 °C to over 23 °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.sup.6, but the absolute polar temperatures that we derive before, during and after the event are more than 10 °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.sup.7 or hurricane-induced ocean mixing.sup.8--to amplify early Palaeogene polar temperatures., Author(s): Appy Sluijs [sup.1] , Stefan Schouten [sup.2] , Mark Pagani [sup.3] , Martijn Woltering [sup.2] , Henk Brinkhuis [sup.1] , Jaap S. Sinninghe Damsté [sup.2] [sup.4] , Gerald R. [...]

Researchers have found methane-rich gas hydrates in sediments of the deep ocean and beneath permafrost regions, which if liberated, could supply bountiful energy or perturb global climate. Because methane is about ten times more powerful a greenhouse gas than carbon dioxide, its release could have resulted in a potentially abrupt climate change.

Generic models of continental-margin evolution predict that siliciclastic fluxes to slopes should be maximal and minimal during major sea-level lowstands and transgressions, respectively. Here we document the opposite for the northeast Australian margin, the largest extant mixed siliciclastic-carbonate depositional system. Cores from slopes of this margin consistently contain siliciclastic-rich intervals, ~0.3-1 m thick, in the upper few meters. Radiocarbon dates of planktonic foraminifera show that this interval was deposited between 12 and 7 ka and represents greatly increased siliciclastic fluxes during late transgression. This massive terrigenous discharge to slopes occurred along at least 450 km of the margin, irrespective of modern variations in bathymetry or climate. Although we cannot dismiss a significantly different early Holocene climate with greatly enhanced sediment discharge, available data instead suggest that rivers aggraded on the shelf during lowstand because of an extensive subaerially exposed reef system. This phenomenon may occur on other margins rimmed by reefs, requiring a major revision of concepts used to interpret mixed siliciclastic-carbonate systems. Keywords: Great Barrier Reef, sequence stratigraphy, sedimentation rates, transgression, late Quaternary, Last Glacial Maximum.

The widespread presence of bottom-simulating reflectors (BSRs) on continental margins has bolstered suggestions that gas hydrates and free gas constitute a large dynamic reservoir of C[H.sub.4] carbon and a vast potential source of energy. However, only a few hydrate-bearing areas have been drilled, and of these, the amount of C[H.sub.4] has only been directly quantified in 18 discrete samples from 3 holes on Blake Ridge, east of Georgia. Here we report and discuss 30 direct measurements of C[H.sub.4] concentration in sediments above and below the BSR at Hydrate Ridge on a tectonically active margin offshore Oregon. High C[H.sub.4] concentrations (71-3127 mM) support abundant gas hydrate (occupying an average of ~11% of porosity) and free gas (occupying ~4% of porosity in 1 sample) in a restricted area where hydrocarbon gases migrate from the deep accretionary complex to the seafloor. In a larger area lacking this hydrocarbon supply, lower C[H.sub.4] concentrations (10-893 mM) indicate less gas hydrate (average ~1% of porosity) and little or no free gas. Overall, the amount of C[H.sub.4] at Hydrate Ridge is significantly less than that at Blake Ridge. These results challenge certain interpretations, including the global volume of hydrate-bound C[H.sub.4], which though large, may be four to seven times less than widely cited estimates. Speculations on the distribution and role of gas hydrate and free gas need revision. Keywords: methane, gas hydrate, Hydrate Ridge, ODP Leg 204.