Transient simulation of the last glacial inception. Part I: glacial inception as a bifurcation in the climate system   总被引：2，自引：2，他引：0  

Reinhard Calov  Andrey Ganopolski  Martin Claussen  Vladimir Petoukhov  Ralf Greve 《Climate Dynamics》2005,24(6):545-561

We study the mechanisms of glacial inception by using the Earth system model of intermediate complexity, CLIMBER-2, which encompasses dynamic modules of the atmosphere, ocean, biosphere and ice sheets. Ice-sheet dynamics are described by the three-dimensional polythermal ice-sheet model SICOPOLIS. We have performed transient experiments starting at the Eemiam interglacial, at 126 ky BP (126,000 years before present). The model runs for 26 kyr with time-dependent orbital and CO₂ forcings. The model simulates a rapid expansion of the area covered by inland ice in the Northern Hemisphere, predominantly over Northern America, starting at about 117 kyr BP. During the next 7 kyr, the ice volume grows gradually in the model at a rate which corresponds to a change in sea level of 10 m per millennium. We have shown that the simulated glacial inception represents a bifurcation transition in the climate system from an interglacial to a glacial state caused by the strong snow-albedo feedback. This transition occurs when summer insolation at high latitudes of the Northern Hemisphere drops below a threshold value, which is only slightly lower than modern summer insolation. By performing long-term equilibrium runs, we find that for the present-day orbital parameters at least two different equilibrium states of the climate system exist—the glacial and the interglacial; however, for the low summer insolation corresponding to 115 kyr BP, we find only one, glacial, equilibrium state, while for the high summer insolation corresponding to 126 kyr BP only an interglacial state exists in the model.

---

Reinhard CalovEmail:

  相似文献   

Late- and post-Variscan cooling and exhumation history of the northern Rhenish massif and the southern Ruhr Basin: new constraints from fission-track analysis     

Harald Karg  Andrew Carter  Manfred R. Brix  Ralf Littke 《International Journal of Earth Sciences》2005,94(2):180-192

Apatite fission-track analyses were carried out on outcrop and core samples from the Rhenish massif and the Carboniferous Ruhr Basin/Germany in order to study the late- and post-Variscan thermal and exhumation history. Apatite fission-track ages range from 291±15 Ma (lower Permian) to 136±7 Ma (lower Cretaceous) and mean track lengths vary between 11.6 m and 13.9 m, mostly displaying unimodal distributions with narrow standard deviations. All apatite fission-track ages are younger than the corresponding sample stratigraphic age, indicating substantial post-depositional annealing of the apatite fission-tracks. This agrees with results from maturity modelling, which indicates 3500–7000 m eroded Devonian and Carboniferous sedimentary cover. Numerical modelling of apatite fission-track data predicts onset of exhumation and cooling not earlier than 320 Ma in the Rhenish massif and 300 Ma in the Ruhr Basin, generally followed by late Carboniferous–Triassic cooling to below 50–60°C. Rapid late Variscan cooling was followed by moderate Mesozoic cooling rates of 0.1–0.2°C/Ma, converting into denudation rates of <1 mm/a (assuming a stable geothermal gradient of 30°C/km). Modelling results also give evidence for some late Triassic and early Jurassic heating and/or burial, which is supported by sedimentary rocks of the same age preserved at the rim of the lower Rhine Basin and in the subsurface of the Central and Northern Ruhr Basin. Cenozoic exhumation and cooling of the Rhenish massif is interpreted as an isostatic response to former erosion and major base-level fall caused by the subsidence in the lower Rhine Basin.  相似文献   

Late Quaternary polycystine radiolarian datum events in the Sea of Okhotsk   总被引：2，自引：0，他引：2  

Alexander Matul  Andrea Abelmann  Ralf Tiedemann  Andre Kaiser  Dirk Nürnberg 《Geo-Marine Letters》2002,22(1):25-32

Five radiolarian datum events have been recorded in the Late Quaternary sediment section from the Sea of Okhotsk, using age assignments based on oxygen-isotope stratigraphy: the last occurrence datum (LOD) of Stylacontarium acquilonium (at about 329 ka), the LOD of Spongodiscus sp. (at about 287 ka), the LOD of Amphimelissa setosa (at about 72 ka), the LOD of Lychnocanoma nipponica sakaii (at about 28 ka), and the L. nipponica sakaii acme event (at about 72 ka). The LODs of S. acquilonium, Spongodiscus sp. and A. setosa appear to be synchronous in comparison with those in the Subarctic North Pacific, but the LOD and the acme event of L. nipponica sakaii show an apparent diachroneity with the corresponding North Pacific events.  相似文献   

The future of chemical in situ sensors     

Ralf D. Prien 《Marine Chemistry》2007

Many of the sampling methods used in oceanographic sciences today date back decades, if not centuries. Although there has been a marked change in how sampling for chemical oceanography is carried out it still relies on taking samples of seawater from a research vessel in most cases. Assessing processes on small timescales as well as transient events requires higher temporal and spatial resolution of measurements; long time series stations require high duration deployments of instruments. Both requirements can only be adequately satisfied by in situ sensors; for the physical parameters off the shelf instruments are available, in the field of chemical oceanography only a few parameters, such as oxygen, are covered by off the shelf instruments, for most parameters adequate instrumentation only exists in the form of prototypes, if at all. Chemical in situ sensors are needed to gain new insights in how the oceans and the life in it works.  相似文献   

Reduced Sensitivity of Tropical Cyclone Intensity and Size to Sea Surface Temperature in a Radiative-Convective Equilibrium Environment     

Shuai WANG  Ralf TOUMI 《大气科学进展》2018,35(8):981-993

It has been challenging to project the tropical cyclone(TC) intensity,structure and destructive potential changes in a warming climate.Here,we compare the sensitivities of TC intensity,size and destructive potential to sea surface warming with and without a pre-storm atmospheric adjustment to an idealized state of Radiative-Convective Equilibrium(RCE).Without RCE,we find large responses of TC intensity,size and destructive potential to sea surface temperature(SST) changes,which is in line with some previous studies.However,in an environment under RCE,the TC size is almost insensitive to SST changes,and the sensitivity of intensity is also much reduced to 3%?C-1–4%?C-1.Without the pre-storm RCE adjustment,the mean destructive potential measured by the integrated power dissipation increases by about 25%?C-1 during the mature stage.However,in an environment under RCE,the sensitivity of destructive potential to sea surface warming does not change significantly.Further analyses show that the reduced response of TC intensity and size to sea surface warming under RCE can be explained by the reduced thermodynamic disequilibrium between the air boundary layer and the sea surface due to the RCE adjustment.When conducting regional-scale sea surface warming experiments for TC case studies,without any RCE adjustment the TC response is likely to be unrealistically exaggerated.The TC intensity–temperature sensitivity under RCE is very similar to those found in coupled climate model simulations.This suggests global mean intensity projections under climate change can be understood in terms of a thermodynamic response to temperature with only a minor contribution from any changes in large-scale dynamics.  相似文献   

Characterization and Parametrization of Reynolds Stress and Turbulent Heat Flux in the Stably-Stratified Lower Arctic Troposphere Using Aircraft Measurements   总被引：1，自引：1，他引：0  

Amir A. Aliabadi  Ralf M. Staebler  Michael Liu  Andreas Herber 《Boundary-Layer Meteorology》2016,161(1):99-126

  相似文献   

Source rock potential of the Middle Jurassic to Middle Pliocene,onshore Nile Delta Basin,Egypt     

Bandar I. Ghassal  Haytham El Atfy  Victoria Sachse  Ralf Littke 《Arabian Journal of Geosciences》2016,9(20):744

Organic geochemical characterization of cutting samples from the Abu Hammad-1 and Matariya-1 wells elucidates the depositional environment and source rock potential of the Jurassic and Lower Cretaceous successions and the Middle Miocene to Pleistocene section in the southern and eastern Nile Delta Basin. The burial and thermal histories of the Mesozoic and Miocene sections were modeled using 1D basin modeling based on input data from the two wells. This study reveals fair to good gas-prone source rocks within the Upper Jurassic and Lower Cretaceous sections with total organic carbon (TOC) averaging 2.7% and hydrogen index (HI) up to 130 mg HC/g TOC. The pristane/n-C₁₇ versus phytane/n-C₁₈ correlation suggests mixed marine and terrestrial organic matter with predominant marine input. Burial and thermal history modeling reveals low thermal maturity due to low heat flow and thin overburden. These source rocks can generate gas in the western and northern parts of the basin where they are situated at deeper settings. In contrast, the thick Middle Miocene shows fair source rock quality (TOC averaging at 1.4%; HI maximizing at 183 mg HC/g TOC). The quality decreases towards the younger section where terrestrial organic matter is abundant. This section is similar to previously studied intervals in the eastern Nile Delta Basin but differs from equivalents in the central parts where the quality is better. Based on 1D modeling, the thick Middle Miocene source rocks just reached the oil generation stage, but microbial gas, however, is possible.  相似文献   

Impact of Lateglacial cold events on the northern Aegean region reconstructed from marine and terrestrial proxy data     

Ulrich Kotthoff  Andreas Koutsodendris  Jörg Pross  Gerhard Schmiedl  André Bornemann  Christian Kaul  Gianluca Marino  Odile Peyron  Ralf Schiebel 《第四纪科学杂志》2011,26(1):86-96

  相似文献   

Catchment‐wide denudation rates at the margin of NE Tibet from in situ‐produced cosmogenic 10Be     

Luigi Palumbo  Ralf Hetzel  Mingxin Tao  Xiaobin Li 《地学学报》2011,23(1):42-48

  相似文献   

Computational modeling of flow‐induced anisotropy of polar ice for the EDML deep drilling site,Antarctica: The effect of rotation recrystallization and grain boundary migration     

Swantje Bargmann  Hakime Seddik  Ralf Greve 《国际地质力学数值与分析法杂志》2012,36(7):892-917

  相似文献