Abstract: The Antarctic Vostok ice core provided compelling evidence of the nature of climate, and of climate feedbacks, over the past 420,000 years. Marine records suggest that the amplitude of climate variability was smaller before that time, but such records are often poorly resolved. Moreover, it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records. Here we report the recovery of a deep ice core from Dome C, Antarctica, that provides a climate record for the past 740,000 years. For the four most recent glacial cycles, the data agree well with the record from Vostok. The earlier period, between 740,000 and 430,000 years ago, was characterized by less pronounced warmth in interglacial periods in Antarctica, but a higher proportion of each cycle was spent in the warm mode. The transition from glacial to interglacial conditions about 430,000 years ago (Termination V) resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases, but there are significant differences in the patterns of change. The interglacial stage following Termination V was exceptionally long—28,000 years compared to, for example, the 12,000 years recorded so far in the present interglacial period. Given the similarities between this earlier warm period and today, our results may imply that without human intervention, a climate similar to the present one would extend well into the future.
EPICA community members* (participants are listed alphabetically)
Laurent Augustin1, Carlo Barbante2, Piers R. F. Barnes3, Jean Marc Barnola1, Matthias Bigler4, Emiliano Castellano5, Olivier Cattani6,
Jerome Chappellaz1, Dorthe Dahl-Jensen7, Barbara Delmonte1,8, Gabrielle Dreyfus6, Gael Durand1, Sonia Falourd6, Hubertus Fischer9,
Jacqueline Fluckiger4, Margareta E. Hansson10, Philippe Huybrechts9, Gerard Jugie11, Sigfus J. Johnsen7, Jean Jouzel6, Patrik Kaufmann4,
Josef Kipfstuhl9, Fabrice Lambert4, Vladimir Y. Lipenkov12, Genevieve C. Littot3, Antonio Longinelli13, Reginald Lorrain14, Valter Maggi8,
Valerie Masson-Delmotte6, Heinz Miller9, Robert Mulvaney3, Johannes Oerlemans15, Hans Oerter9, Giuseppe Orombelli8, Frederic Parrenin1,6,
David A. Peel3, Jean-Robert Petit1, Dominique Raynaud1, Catherine Ritz1, Urs Ruth9, Jakob Schwander4, Urs Siegenthaler4, Roland Souchez14,
Bernhard Stauffer4, Jorgen Peder Steffensen7, Barbara Stenni16, Thomas F. Stocker4, Ignazio E. Tabacco17, Roberto Udisti5,
Roderik S. W. van de Wal15, Michiel van den Broeke15, Jerome Weiss1, Frank Wilhelms9, Jan-Gunnar Winther18, Eric W. Wolff3 & Mario Zucchelli19*
1, Laboratoire de Glaciologie et Geophysique de l’Environnement (CNRS), BP 96, 38402 St Martin d’Heres Cedex, France; 2, Environmental Sciences Department,
University of Venice, Calle Larga S. Marta, 2137, I-30123 Venice, Italy; 3, British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK; 4, Climate
and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland; 5, Department of Chemistry—Analytical Chemistry
Section, Scientific Pole—University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino (Florence), Italy; 6, Institut Pierre Simon Laplace/Laboratoire des Sciences
du Climat et de l’Environnement, UMR CEA-CNRS 1572, CE Saclay, Orme des Merisiers, 91191 Gif-Sur-Yvette, France; 7, Niels Bohr Institute for Astronomy, Physics
and Geophysics, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark; 8, University of Milano-Bicocca, Dipartimento di Scienze Ambiente
e Territorio, Piazza della Scienza 1, I-20126 Milan, Italy; 9, Alfred-Wegener-Institute for Polar- und Marine Research (AWI), Postfach 120161, D-27515 Bremerhaven,
Germany; 10, Department of Physical Geography and Quaternary Geology, Stockholm University, S-106 91 Stockholm, Sweden; 11, Institut Polaire Francais–Paul Emile Victor (IPEV), BP 75, 29280 Plouzane, France; 12, Arctic and Antarctic Research Institute, 38 Beringa Street, 199397 St Petersburg, Russia; 13, Department of Earth Sciences, University of Parma, Parco Area delle Scienze 157/A, I-43100 Parma, Italy; 14, Departement des Sciences de la Terre et de l’Environnement, Faculte des Sciences, CP 160/03, Universite Libre de Bruxelles, 50 avenue FD Roosevelt, B1050 Brussels, Belgium; 15, Institute for Marine and Atmospheric Research Utrecht
(IMAU), Princetonplein 5, 3584 CC Utrecht, The Netherlands; 16, Department of Geological, Environmental and Marine Sciences, University of Trieste, Via E. Weiss 2,
I-34127 Trieste, Italy; 17, Earth Science Department, University of Milan, Via Cicognara 7, 20129 Milano, Italy; 18, Norwegian Polar Institute, N-9296 Tromsø, Norway;
19, ENEA, CRE Casaccia, PO Box 2400, Via Anguillarese 301, 00060 S. Maria di Galleria (RM), Italy.
*Deceased.

Abstract: Water stable isotope measurements (?D and ?18O) have been conducted on the Holocene part of two deep Greenland ice cores (Greenland Ice Core Project (GRIP) and NorthGRIP), located ?320 km apart. These combined measurements provide the first two continuous Greenland Holocene deuterium excess profiles (d = ?D ? 8?18O), a parameter strongly influenced by changes in moisture sources. We discuss here temporal and regional fluctuations of the deuterium excess within central to north Greenland, with a mean temporal resolution of ?4 years. Although GRIP and NorthGRIP exhibit similar annual mean surface temperatures and ?18O levels, a significant offset of modern deuterium excess is observed between the two sites. We attribute this offset to a different mix of modern moisture sources, pointing to regional-scale differences in moisture advection toward Greenland. The common long-term deuterium excess Holocene increasing trend is probably related to the increased relative contribution of low-latitude moisture to Greenland snowfall, in response to the change in the Earth obliquity, as symmetrically observed in Antarctica. Three abrupt declines punctuate the GRIP excess record (8.2, 4.5, and 0.35 ka BP), suggesting associated reorganizations of the northern high latitudes hydrological cycle. The 8.2 ka BP event is characterized by (1) a rapid cooling followed by a progressive warming and (2) a deuterium excess cooling restricted to GRIP, therefore totally different from rapid events during glacial times. By contrast, the NorthGRIP deuterium excess record is more stable. We propose that a slightly larger proportion of moisture supplied by local storm tracks to GRIP induces an isotopic compensation mechanism between simultaneous site and source temperature coolings, resulting in a rather temperature-insensitive ?18O profile, together with well-marked deuterium excess amplitudes. NorthGRIP ?18O seems less biased by isotopic processes and should provide a more reliable past temperature record.

Abstract: Spherical cap harmonic analysis (SCHA) has become a common tool for the regional modeling of potential fields since its introduction by Haines (1985). The fact that SCHA satisfies Laplace equation and the possibility of representing high-frequency fields with a small number of coefficients (compared to the global spherical harmonic analysis) made SCHA the preferred choice for the development, for example, of magnetic field models at national scale. However, Thébault et al. (2006a) demonstrated that the traditional SCHA presented some deficiencies, in particular related to the inversion of multilevel data sets. The authors presented the R-SCHA technique as an alternative method in which the introduction of a new set of basis functions and boundary conditions solved this issue. In this paper we present some numerical comparisons between the SCHA and R-SCHA techniques applied with different synthetic vector data sets, from near-surface main field, main difference, and crustal field data simulating a World Digital Magnetic Anomaly Map subset. Other analyses are carried out with synthetic vector data set that mimics the expected data distribution from a multisatellite mission like the forthcoming European Swarm mission. No regularization, weighting, or ad hoc procedures are applied to the synthetic vector data, and a cap of 7° aperture is considered. The numerical analyses show that SCHA is a satisfying approximation in a band-limited spectral region that depends on the cap's size. It does not work correctly either for main field or for the short-scale crustal field modeling. These aspects are supported by equations illustrating why SCHA may fail. On the contrary, R-SCHA converges more slowly than SCHA but is valid in all cases. It gives a consistent set of regional coefficients and fits the radial variation of the field in a realistic way. At last, the special case of data incompatibility shows that R-SCHA does not fit incompatible data while SCHA assimilates most of them. These results should help the scientific community to evaluate the level of approximation needed for the development of regional magnetic field models in the era of the European Space Agency Swarm mission.

Abstract: As already discussed in the preceding chapters, life at low temperatures is abundant, diverse and widespread, with organisms from all three domains of life being represented. Bacteria and archaea at thermal equilibrium with their environment are found to be preponderant, and these cold-adapted, or psychrophilic, microorganisms have been found to not only endure, but to flourish under the harsh conditions of permanently low-temperatures. In fact, for some, this environment is not only optimal, but mandatory for sustained cell proliferation, with moderate to high temperatures (e.g., >12°C) being deleterious (Xu et al. 2003c).

Abstract: Abstract  Snow surfaces play an important role in the biogeochemical cycle of mercury in high-latitude regions. Snowpacks act both as sources and sinks for gaseous compounds. Surprisingly, the roles of each environmental parameter that can govern the air–surface exchange over snow are not well understood owing to the lack of systematic studies. A laboratory system called the laboratory flux measurement system was used to study the emission of gaseous elemental mercury from a natural snowpack under controlled conditions. The first results from three snowpacks originating from alpine, urban and polar areas are presented. Consistent with observations in the field, we were able to reproduce gaseous mercury emissions and showed that they are mainly driven by solar radiation and especially UV-B radiation. From these laboratory experiments, we derived kinetic constants which show that divalent mercury can have a short natural lifetime of about 4–6 h in snow.