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Torben Koenigk Christof K?nig Beatty Mihaela Caian Ralf D?scher Klaus Wyser 《Climate Dynamics》2012,38(11-12):2389-2408
Decadal prediction is one focus of the upcoming 5th IPCC Assessment report. To be able to interpret the results and to further improve the decadal predictions it is important to investigate the potential predictability in the participating climate models. This study analyzes the upper limit of climate predictability on decadal time scales and its dependency on sea ice albedo parameterization by performing two perfect ensemble experiments with the global coupled climate model EC-Earth. In the first experiment, the standard albedo formulation of EC-Earth is used, in the second experiment sea ice albedo is reduced. The potential prognostic predictability is analyzed for a set of oceanic and atmospheric parameters. The decadal predictability of the atmospheric circulation is small. The highest potential predictability was found in air temperature at 2?m height over the northern North Atlantic and the southern South Atlantic. Over land, only a few areas are significantly predictable. The predictability for continental size averages of air temperature is relatively good in all northern hemisphere regions. Sea ice thickness is highly predictable along the ice edges in the North Atlantic Arctic Sector. The meridional overturning circulation is highly predictable in both experiments and governs most of the decadal climate predictability in the northern hemisphere. The experiments using reduced sea ice albedo show some important differences like a generally higher predictability of atmospheric variables in the Arctic or higher predictability of air temperature in Europe. Furthermore, decadal variations are substantially smaller in the simulations with reduced ice albedo, which can be explained by reduced sea ice thickness in these simulations. 相似文献
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Georges Clauzon Jean-Pierre Suc† Speranta-Maria Popescu† Mariana Marunteanu‡ Jean-Loup Rubino¶ Florian Marinescu‡ Mihaela Carmen Melinte§ 《Basin Research》2005,17(3):437-462
A recently published scenario viewing the Messinian salinity crisis as two evaporitic steps rather than one has led to a search for new indices of the crisis in the Eastern Paratethys. Fluvial processes characterized the southwestern Dacic Basin (Southern Romania, i.e. the Carpathian foredeep) whereas brackish sediments were continuously deposited in its northern part. This is consistent with previously evidenced responses of the Black Sea to the Messinian salinity crisis. High sea‐level exchanges between the Mediterranean Sea and Eastern Paratethys are considered to have occurred just before and just after desiccation of the Mediterranean. This accounts for two successive Mediterranean nannoplankton‐dinocyst influxes into the Eastern Paratethys that, respectively, belong to zones NN 11 and NN 12. Meanwhile, two separate events that gave rise to Lago Mare facies (with Paratethyan Congeria, ostracods and/or dinoflagellate cysts) arose in the Mediterranean Basin in response to these high sea‐level exchanges and located 5.52 and 5.33 Ma (isotopic stages TG 11 and TG 5, respectively), i.e. just before and just after the almost complete desiccation of the Mediterranean). These Lago Mare facies formed independently of lakes with ostracods of the Cyprideis group that developed in the central basins during the final stages of desiccation. The gateway faciliting these water exchanges is not completely identified. A proto‐Bosphorus strait seems unlikely. A plausible alternative route extends from the northern part of the Thessaloniki region up to the Dacic Basin and through Macedonia and the Sofia Basin. The expression ‘Lago Mare’ is chronostratigraphically ambiguous and should be discontinued for this purpose, although it might remain useful as a palaeoenvironmental term. 相似文献
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Quantitative analysis of variations in morphological types of charcoal were undertaken in sediment cores from three lakes
on the Interior Plateau (BC, Canada) over the period AD 1919–2000. Seven distinct morphological types of charcoal were identified
based on particle shape and structural features and were compared with seasonal precipitation and recorded area burned within
20 km-radius of study lakes. Fragile-type charcoal fragments, termed type M, displayed significant relationships to recorded
area burned in sediment cores from Prosser (r
2 = 0.5; p = 0.0001) and Opatcho (r
2 = 0.2; p = 0.02) lakes. However, nonsignificant correlations (p > 0.05) were found between total charcoal and area burned. Robust and highly elongated morphotypes C and F were correlated
to recorded spring precipitation (r
2 = 0.5; p = 0.002) in Opatcho Lake. Charcoal from a sediment core from Big Lake, the lake with the largest watershed, was significantly
but inversely related to past fires (r
2 = 0.44; p = 0.0003), suggesting important contributions from secondary transportation and deposition. Models were developed to infer
relative area burned and precipitation for the study lakes. Our results suggest that charcoal morphotypes are related to the
biogeoclimatic and lake watershed characteristics. This study also suggest that charcoal morphotypes can provide insights
on past fire and climate, which was not possible based on traditional analysis of total charcoal. 相似文献
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Vrancea is one of the few singular seismic regions of the world where intermediate-depth earthquakes are permanently generated (around 10 events/month with M
L
> 3) within an extremely confined focal volume. This particularity and the relatively large number of short-period waveforms recorded by the Romanian local network provides us the opportunity to test the performance of the empirical Green's function technique in retrieving the source time function and source directivity of the Vrancea earthquakes. Three earthquakes that occurred on March 11, 1983 (M
L
= 5.4), April 12, 1983 (M
L
= 5.1) and August 7, 1984 (M
L
= 5.1) in the lower part of the subducting lithosphere (h 150 km) were analyzed. A set of 28 adjacent events (3.0 < M
L
< 4.4) which occurred between 1981 and 1997 were selected as corresponding empirical Green's functions. To test the confidence of the retrieved source time function, we compare the deconvolved pulses using Green's functions of different sizes and recorded simultaneously by short-period and broad-band instruments. Our tests show that the durations of the source time function is well-constrained and is not affected by the limited frequency range of the short-period instruments, or by the relative difference in the focal mechanism between the main event and Green's event. The apparent duration of the source time function outlines source directivity effects, and when these effects are sufficiently strong, they can identify the real fault plane. Relatively short source duration and correspondingly high stress drop values are in agreement with other previous results emphasizing a specific seismic regime in the lower part of the Vrancea subducting lithosphere. 相似文献
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François Bache Speranta‐Maria Popescu Marina Rabineau Christian Gorini Jean‐Pierre Suc Georges Clauzon Jean‐Louis Olivet Jean‐Loup Rubino Mihaela Carmen Melinte‐Dobrinescu Ferran Estrada Laurent Londeix Rolando Armijo Bertrand Meyer Laurent Jolivet Gwénaël Jouannic Estelle Leroux Daniel Aslanian Antonio Tadeu Dos Reis Ludovic Mocochain Nikola Dumurdžanov Ivan Zagorchev Vesna Lesić Dragana Tomić M. Namık Çağatay Jean‐Pierre Brun Dimitrios Sokoutis Istvan Csato Gülsen Ucarkus Ziyadin Çakır 《Basin Research》2012,24(2):125-153
The Messinian Salinity Crisis is well known to have resulted from a significant drop of the Mediterranean sea level. Considering both onshore and offshore observations, the subsequent reflooding is generally thought to have been very sudden. We present here offshore seismic evidence from the Gulf of Lions and re‐visited onshore data from Italy and Turkey that lead to a new concept of a two‐step reflooding of the Mediterranean Basin after the Messinian Salinity Crisis. The refilling was first moderate and relatively slow accompanied by transgressive ravinement, and later on very rapid, preserving the subaerial Messinian Erosional Surface. The amplitude of these two successive rises of sea level has been estimated at ≤500 m for the first rise and 600–900 m for the second rise. Evaporites from the central Mediterranean basins appear to have been deposited principally at the beginning of the first step of reflooding. After the second step, which preceeded the Zanclean Global Stratotype Section and Point, successive connections with the Paratethyan Dacic Basin, then the Adriatic foredeep, and finally the Euxinian Basin occurred, as a consequence of the continued global rise in sea level. A complex morphology with sills and sub‐basins led to diachronous events such as the so‐called ‘Lago Mare’.This study helps to distinguish events that were synchronous over the entire Mediterranean realm, such as the two‐step reflooding, from those that were more local and diachronous. In addition, the shoreline that marks the transition between these two steps of reflooding in the Provence Basin provides a remarkable palaeogeographical marker for subsidence studies. 相似文献
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James M. Dohm Robert C. Anderson Nadine G. Barlow Hirdy Miyamoto Ashley G. Davies G. Jeffrey Taylor Victor R. Baker William V. Boynton John Keller Kris Kerry Daniel Janes Alberto G. Fairn Dirk Schulze-Makuch Mihaela Glamoclija Lucia Marinangeli Gian G. Ori Robert G. Strom Jean-Pierre Williams Justin C. Ferris J.A.P. Rodríguez Miguel A. de Pablo Suniti Karunatillake 《Planetary and Space Science》2008,56(7):985-1013
The paradigm of an ancient warm, wet, and dynamically active Mars, which transitioned into a cold, dry, and internally dead planet, has persisted up until recently despite published Viking-based geologic maps that indicate geologic and hydrologic activity extending into the Late Amazonian epoch. This paradigm is shifting to a water-enriched planet, which may still exhibit internal activity, based on a collection of geologic, hydrologic, topographic, chemical, and elemental evidences obtained by the Viking, Mars Global Surveyor (MGS), Mars Odyssey (MO), Mars Exploration Rovers (MER), and Mars Express (MEx) missions. The evidence includes: (1) stratigraphically young rock materials such as pristine lava flows with few, if any, superposed impact craters; (2) tectonic features that cut stratigraphically young materials; (3) features with possible aqueous origin such as structurally controlled channels that dissect stratigraphically young materials and anastomosing-patterned slope streaks on hillslopes; (4) spatially varying elemental abundances for such elements as hydrogen (H) and chlorine (Cl) recorded in rock materials up to 0.33 m depth; and (5) regions of elevated atmospheric methane. This evidence is pronounced in parts of Tharsis, Elysium, and the region that straddles the two volcanic provinces, collectively referred to here as the Tharsis/Elysium corridor. Based in part on field investigations of Solfatara Crater, Italy, recommended as a suitable terrestrial analog, the Tharsis/Elysium corridor should be considered a prime target for Mars Reconnaissance Orbiter (MRO) investigations and future science-driven exploration to investigate whether Mars is internally and hydrologically active at the present time, and whether the persistence of this activity has resulted in biologic activity. 相似文献
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