Southern ocean warming, sea level and hydrological change during the Paleocene-Eocene thermal maximum

A brief (~150 kyr) period of widespread global average surface warming marks the transition between the Paleocene and Eocene epochs, ~56 million years ago. This so-called "Paleocene-Eocene thermal maximum" (PETM) is associated with the massive injection of <sup>13</sup>C-depleted carbon, reflected in a negative carbon isotope excursion (CIE). Biotic responses include a global abundance peak (acme) of the subtropical dinoflagellate <i>Apectodinium</i>. Here we identify the PETM in a marine sedimentary sequence deposited on the East Tasman Plateau at Ocean Drilling Program (ODP) Site 1172 and show, based on the organic paleothermometer TEX<sub>86</sub>, that southwest Pacific sea surface temperatures increased from ~26 °C to ~33°C during the PETM. Such temperatures before, during and after the PETM are >10 °C warmer than predicted by paleoclimate model simulations for this latitude. In part, this discrepancy may be explained by potential seasonal biases in the TEX<sub>86</sub> proxy in polar oceans. Additionally, the data suggest that not only Arctic, but also Antarctic temperatures may be underestimated in simulations of ancient greenhouse climates by current generation fully coupled climate models. An early influx of abundant <i>Apectodinium</i> confirms that environmental change preceded the CIE on a global scale. Organic dinoflagellate cyst assemblages suggest a local decrease in the amount of river run off reaching the core site during the PETM, possibly in concert with eustatic rise. Moreover, the assemblages suggest changes in seasonality of the regional hydrological system and storm activity. Finally, significant variation in dinoflagellate cyst assemblages during the PETM indicates that southwest Pacific climates varied significantly over time scales of 10<sup>3</sup> – 10<sup>4</sup> years during this event, a finding comparable to similar studies of PETM successions from the New Jersey Shelf

Paleoceanography and ice sheet variability offshore Wilkes Land, Antarctica – Part 3: Insights from Oligocene–Miocene TEX86-based sea surface temperature reconstructions

The volume of the Antarctic continental ice sheet(s) varied substantially during the Oligocene and Miocene ( 34–5 Ma) from smaller to substantially larger than today, both on million-year and on orbital timescales. However, reproduction through physical modeling of a dynamic response of the ice sheets to climate forcing remains problematic, suggesting the existence of complex feedback mechanisms between the cryosphere, ocean, and atmosphere systems. There is therefore an urgent need to improve the models for better predictions of these systems, including resulting potential future sea level change. To assess the interactions between the cryosphere, ocean, and atmosphere, knowledge of ancient sea surface conditions close to the Antarctic margin is essential. Here, we present a new TEX86- based sea surface water paleotemperature record measured on Oligocene sediments from Integrated Ocean Drilling Program (IODP) Site U1356, offshore Wilkes Land, East Antarctica. The new data are presented along with previously published Miocene temperatures from the same site. Together the data cover the interval between 34 and 11 Ma and encompasses two hiatuses. This record allows us to accurately reconstruct the magnitude of sea surface temperature (SST) variability and trends on both million-year and glacial–interglacial timescales.Julian D. Hartman, Francesca Sangiorgi, Henk Brinkhuis, and Peter K. Bijl acknowledge the NWO Netherlands Polar Program project number 866.10.110. Stefan Schouten was supported by the Netherlands Earth System Science Centre (NESSC), funded by the Dutch Ministry of Education, Culture and Science (OCW). Peter K. Bijl and Francien Peterse received funding through NWO-ALW VENI grant nos. 863.13.002 and 863.13.016, respectively. Carlota Escutia and Ariadna Salabarnada thank the Spanish Ministerio de Econimía y Competitividad for grant CTM2014-60451-C2-1-P. We thank Alexander Ebbing and Anja Bruls for GDGT sample preparation during their MSc research. This research used samples from the Integrated Ocean Drilling Program (IODP). IODP was sponsored by the US National Science Foundation and participating countries under management of Joined Oceanographic Institutions Inc

Quantized vortices and collective oscillations of a trapped Bose condensed gas

Using a sum rule approach we calculate the frequency shifts of the quadrupole oscillations of a harmonically trapped Bose gas due to the presence of a quantized vortex. Analytic results are obtained for positive scattering lengths and large N where the shift relative to excitations of opposite angular momentum is found to be proportional to the quantum circulation of the vortex and to decrease as N^{-2/5}. Results are also given for smaller values of N covering the transition between the ideal gas and the Thomas-Fermi limit. For negative scattering lengths we predict a macroscopic instability of the vortex. The splitting of the collective frequencies in toroidal configurations is also discussed.Comment: Rextex, 4 pages, 1 postscript figur

Fermionization of a bosonic gas under highly-elongated confinement: A diffusion quantum Monte Carlo study

The diffusion quantum Monte Carlo technique is used to solve the many-body Schroedinger equation fully quantum mechanically and nonperturbatively for bosonic atomic gases in cigar-shaped confining potentials. By varying the aspect ratio of the confining potential from 1 (spherical trap) to 10000 (highly elongated trap), we characterize the transition from the three-dimensional regime to the (quasi-)one-dimensional regime. Our results confirm that the bosonic gas undergoes ``fermionization'' for large aspect ratios. Importantly, many-body correlations are included explicitly in our approach.Comment: 10 pages, 8 figure

Real-time pion propagation in finite-temperature QCD

We argue that in QCD near the chiral limit, at all temperatures below the chiral phase transition, the dispersion relation of soft pions can be expressed entirely in terms of three temperature-dependent quantities: the pion screening mass, a pion decay constant, and the axial isospin susceptibility. The definitions of these quantities are given in terms of equal-time (static) correlation functions. Thus, all three quantities can be determined directly by lattice methods. The precise meaning of the Gell-Mann--Oakes--Renner relation at finite temperature is given.Comment: 25 pages, 2 figures; v2: discussion on the region of applicability expanded, to be published in PR

Structure of boson systems beyond the mean-field

We investigate systems of identical bosons with the focus on two-body correlations. We use the hyperspherical adiabatic method and a decomposition of the wave function in two-body amplitudes. An analytic parametrization is used for the adiabatic effective radial potential. We discuss the structure of a condensate for arbitrary scattering length. Stability and time scales for various decay processes are estimated. The previously predicted Efimov-like states are found to be very narrow. We discuss the validity conditions and formal connections between the zero- and finite-range mean-field approximations, Faddeev-Yakubovskii formulation, Jastrow ansatz, and the present method. We compare numerical results from present work with mean-field calculations and discuss qualitatively the connection with measurements.Comment: 26 pages, 6 figures, submitted to J. Phys. B. Ver. 2 is 28 pages with modified figures and discussion

Lipid-biomarker-based sea surface temperature record offshore Tasmania over the last 23 million years

The Neogene (23.04–2.58 Ma) is characterised by progressive buildup of ice volume and climate cooling in the Antarctic and the Northern Hemisphere. Heat and moisture delivery to Antarctica is, to a large extent, regulated by the strength of meridional temperature gradients. However, the evolution of the Southern Ocean frontal systems remains scarcely studied in the Neogene. Here, we present the first long-term continuous sea surface temperature (SST) record of the subtropical front area in the Southern Ocean at Ocean Drilling Program (ODP) Site 1168 off western Tasmania. This site is, at present, located near the subtropical front (STF), as it was during the Neogene, despite a 10∘ northward tectonic drift of Tasmania. We analysed glycerol dialkyl glycerol tetraethers (GDGTs – on 433 samples) and alkenones (on 163 samples) and reconstructed the paleotemperature evolution using TEX86 and U37k′ as two independent quantitative proxies. Both proxies indicate that Site 1168 experienced a temperate ∼ 25 ∘C during the early Miocene (23–17 Ma), reaching ∼ 29 ∘C during the mid-Miocene climatic optimum. The stepwise ∼ 10 ∘C cooling (20–10 ∘C) in the mid-to-late Miocene (12.5–5.0 Ma) is larger than that observed in records from lower and higher latitudes. From the Pliocene to modern (5.3–0 Ma), STF SST first plateaus at ∼ 15 ∘C (3 Ma), then decreases to ∼ 6 ∘C (1.3 Ma), and eventually increases to the modern levels around ∼ 16 ∘C (0 Ma), with a higher variability of 5∘ compared to the Miocene. Our results imply that the latitudinal temperature gradient between the Pacific Equator and the STF during late Miocene cooling increased from 4 to 14 ∘C. Meanwhile, the SST gradient between the STF and the Antarctic margin decreased due to amplified STF cooling compared to the Antarctic margin. This implies a narrowing SST gradient in the Neogene, with contraction of warm SSTs and northward expansion of subpolar conditions.</p