Simulated climate conditions in Europe during the Marine Isotope Stage 3 stadial

Kjellström, E., Brandefelt, J., Näslund, J.‐O., Smith, B., Strandberg, G., Voelker, A. H. L. & Wohlfarth, B. 2010: Simulated climate conditions in Europe during the Marine Isotope Stage 3 stadial. Boreas, 10.1111/j.1502‐3885.2010.00143.x. ISSN 0300‐9483. State‐of‐the‐art climate models were used to simulate climate conditions in Europe during Greenland Stadial (GS) 12 at 44 ka BP. The models employed for these simulations were: (i) a fully coupled atmosphere–ocean global climate model (AOGCM), and (ii) a regional atmospheric climate model (RCM) to dynamically downscale results from the global model for a more detailed investigation of European climate conditions. The vegetation was simulated off‐line by a dynamic vegetation model forced by the climate from the RCM. The resulting vegetation was then compared with the a priori vegetation used in the first simulation. In a subsequent step, the RCM was rerun to yield a new climate more consistent with the simulated vegetation. Forcing conditions included orbital forcing, land–sea distribution, ice‐sheet configuration, and atmospheric greenhouse gas concentrations representative for 44 ka BP. The results show a cold climate on the global scale, with global annual mean surface temperatures 5 °C colder than the modern climate. This is still significantly warmer than temperatures derived from the same model system for the Last Glacial Maximum (LGM). Regional, northern European climate is much colder than today, but still significantly warmer than during the LGM. Comparisons between the simulated climate and proxy‐based sea‐surface temperature reconstructions show that the results are in broad agreement, albeit with a possible cold bias in parts of the North Atlantic in summer. Given a prescribed restricted Marine Isotope Stage 3 ice‐sheet configuration, with large ice‐free regions in Sweden and Finland, the AOGCM and RCM model simulations produce a cold and dry climate in line with the restricted ice‐sheet configuration during GS 12. The simulated temperature climate, with prescribed ice‐free conditions in south‐central Fennoscandia, is favourable for the development of permafrost, but does not allow local ice‐sheet formation as all snow melts during summer.     

Phase relationship and surface water mass change in the Northeast Atlantic during Marine Isotope Stage 11 (MIS 11)

Planktic foraminiferal census data, faunal sea surface temperatures (SSTs) and oxygen isotopic and lithic records from a site in the northeast Atlantic were analyzed to study the interglacial dynamics of Marine Isotope Stage (MIS) 11, a period thought to closely resemble the Holocene on the basis of orbital forcing. Interglacial conditions during MIS 11 persisted for approximately 26 ka. After the main deglacial meltwater processes ceased, a 10- to 12-ka-long transitional period marked by significant water mass circulation changes occurred before surface waters finally reached their thermal maximum. This SST peak occurred between 400 and 397 ka, inferred from the abundance of the most thermophilic foraminiferal species and was coincident with lowest sea level according to benthic isotope values. The ensuing stepwise SST decrease characterizes the overall climate deterioration preceding the increase in global ice volume by  3 ka. This cooling trend was followed by a more pronounced cold event that began at 388 ka, and that terminated in the recurrence of icebergs at the site around 382 ka. Because the water mass configuration of early MIS 11 evolved quite differently from that of the early Holocene, there is little evidence that MIS 11 can serve as an appropriate analogue for a future Holocene climate, despite the similarity in some orbital parameters.     

Palaeotemperature reconstructions of the European permafrost zone during marine oxygen isotope Stage 3 compared with climate model results

A palaeotemperature reconstruction based on periglacial phenomena in Europe north of approximately 51 °N, is compared with high‐resolution regional climate model simulations of the marine oxygen isotope Stage 3 (Stage 3) palaeoclimate. The experiments represent Stage 3 warm (interstadial), Stage 3 cold (stadial) and Last Glacial Maximum climatic conditions. The palaeotemperature reconstruction deviates considerably for the Stage 3 cold climate experiments, with mismatches up to 11 °C for the mean annual air temperature and up to 15 °C for the winter temperature. However, in this reconstruction various factors linking climate and permafrost have not been taken into account. In particular a relatively thin snow cover and high climatic variability of the glacial climate could have influenced temperature limits for ice‐wedge growth. Based on modelling the 0 °C mean annual ground temperature proves to be an appropriate upper temperature limit. Using this limit, mismatches with the Stage 3 cold climate experiments have been reduced but still remain. We therefore assume that the Stage 3 ice wedges were generated during short (decadal time‐scale) intervals of extreme cold climate, below the mean temperatures indicated by the Stage 3 cold climate model simulations. Copyright © 2003 John Wiley & Sons, Ltd.     

Spatially variable sedimentary responses to orbitally driven pluvial climate during Marine Oxygen Isotope Stage 5.1, Dakhla Oasis region, Egypt

Pleistocene basinal sediments (PBS) in the Dakhla region of Egypt's hyperarid Western Desert comprise four facies: (A) fluvio-lacustrine, (B) mixed lacustrine/pluvio-eolian, (C) pluvio-eolian, and (D) mixed eolian/pluvio-eolian. Contiguity of basins containing each facies, and their stratigraphic position between two bajada gravel formations, P/B-II and P/B-III, confirm their equivalence. Facies A and B, with lacustrine components, are attributed to orbitally forced poleward incursion of the Intertropical Convergence Zone (ITCZ), resulting in increased summer insolation/temperature/precipitation. Facies C and D, comprising pluvio-eolian and eolian sediments, reflect geologic/topographic influences overprinted on regional 'pluvial' conditions, eliminating lacustrine response. A Th/U age of ∼ 62 ka on lacustrine marl within Facies B is minimal, and an OSL age of 110 ± 18 ka on sediments immediately below Facies B is maximal. Since bajada gravels P/B-III are the youngest Pleistocene formation, they must represent the final strong incursion of the ITCZ into the Dakhla region at MIS 5.1, ∼ 80 ka. Because PBS Facies A pass rapidly up into P/B-III bajada gravels, PBS are assigned to the rising limb of the MIS 5.1 insolation/temperature/precipitation curve, slightly younger than 80 ka.     

Uncertainties in estimates of the impact of recent climate variations on groundwater

Objective and subjective uncertainties in modern estimates of the impact of long-term climate variations on the subsurface runoff and groundwater reserves are discussed. It is shown that the assessment of groundwater reserves should take into consideration the insufficient reliability of the main hydrogeological parameters and estimates of their likely changes. Therefore, the prediction of the influence of climate changes on groundwater reserves and its regime is now impossible. The mechanism of the natural floral damping of possible changes in the groundwater replenishment and temperature–moisture regime of large regions determined by climate changes due to the growing greenhouse gas concentration in the troposphere is described for the first time.     

白垩纪“温室”气候与海洋

白垩纪典型的"温室"气候和海洋一直是地学界关注的焦点之一.与现今地球"冰室"状态相比,温室状态下的气候和海洋遵循着不同的运行模式.本文在近年来取得的大量同位素、古生物以及气候和海洋模拟实验数据的基础上,评述了白垩纪古气候和古海洋研究中取得的重要进展.化石氧同位素数据揭示白垩纪全球平均气温比现今高3～10℃,海洋纬向温度梯度仅0.15～0.3℃/1°,全球海洋结构和大洋环流可能与现今完全不同,大洋环流的驱动很可能是盐度变化而不是温度差异.白垩纪深水沉积显示出从早白垩世碳酸盐台地相、含黑色页岩夹层、黑色页岩和大洋红层大规模出现一直到晚白垩世整体以大洋红层为主的转变.对该沉积转变机制及其与古海洋、古气候关系的研究正是IGCP463/494的主要科学目标.     

Comparison of the Climate during Marine Isotope Stage 9 and 11 Inferred from a Speleothem Isotope Record from Northern Norway

A stalagmite from northern Norway is dated with 12 thermal ionization mass spectrometry U-Th dates, and at least four separate growth periods are identified that correspond with marine isotope stages 9, 11, 13, and probably 15. The calcite is tested for isotopic equilibrium with the Hendy test. Oxygen isotope measurements on 231 subsamples on a vertical transect are used as a paleotemperature proxy. The detailed isotopic record from MIS 9 show apparent similarities to a Holocene record from the same cave, both in the climatic evolution and the overall temperatures: both show temperature oscillations changing from high-frequency, low-amplitude cycles in the beginning of the interglacial period to lower frequency, higher amplitude cycles in the later part of the interglacial period. The isotope record from MIS 11 shows a distinct isotopic event toward heavier values. The isotopic record together with the porous, humus-rich calcite are interpreted as indicating a warmer than present interglacial period with several episodes of heavy rainfall.     

全新世中期中国气候格局定量重建

古气候要素的定量化,是认识气候变化规律的关键节点之一。以往对于我国的古气候要素定量化重建,主要基于孢粉-气候的统计学方法。由于该方法难以有效区分温度、降水和大气CO₂浓度等环境因子对植物生长的影响,因而导致重建结果可能存在不确定性。本次研究,我们基于植物生理过程、新一代古气候定量重建的植被反演方法,考虑环境因子对植被生长的影响,利用新完善的中国第四纪孢粉数据库中的孢粉数据,定量化重建了我国全新世中期（6±0.5ka ¹⁴C）的古气候要素空间格局。结果表明,全新世中期我国年均温度比现在略高约0.7℃,东部区域增温明显,尤其是东北地区,而西北地区可能略有降温;最冷月温度增温较大,达约1℃,而最热月温度增温较小,为约0.5℃。全国年降水量整体比现在多约230mm,主要是夏季降水增多所导致,其中东部地区增加显著。上述结果揭示,全新世中期全球增温将有利于我国降水增加,并导致季节性温度变化明显。本次重建结果增强了与古气候模拟结果的可对比性。

     

泥河湾盆地上新世-更新世过渡时期野火与植被和气候变化

上新世-更新世过渡时期是地球气候由相对温暖的上新世向第四纪冰期-间冰期旋回模式转变的重要阶段, 也是现代气候和生态系统形成过程中的关键时期。野火作为地球生态系统重要的扰动因子, 直接影响着地球生态环境结构和功能的演变, 对维持地球生态系统平衡具有重要作用。本研究通过对泥河湾盆地NHA钻孔(175.2~106.0 m段)上新世-更新世过渡时期(2.89~1.78 Ma)333个沉积物样品的炭屑分析, 并结合孢粉分析结果, 揭示了泥河湾盆地上新世-更新世过渡时期野火活动历史, 探讨了研究段内泥河湾盆地野火活动对区域气候、植被变化的响应特征以及野火强度与火频率的关系。研究结果显示: 1)泥河湾盆地上新世-更新世过渡时期野火强度总体可以分为1个火强度较大的时期(2.74~2.32 Ma)和2个火强度较小的时期(2.89~2.74 Ma和2.32~1.78 Ma); 2)炭屑总浓度以及>125 μm粗粒炭屑浓度均表现出显著的41 ka斜率周期, 表明泥河湾盆地野火活动强度受高纬冰量驱动影响显著; 3)可燃生物量是影响野火强度的最主要因素, 而植被类型对野火强度的影响较小; 4)火强度与火频率的变化不完全同步, 表现为强度大-频率高、强度大-频率低以及强度小-频率高的3种模式; 5)2.60~2.14 Ma是研究段泥河湾盆地野火活动最强的时期, 表现为火强度大-频率高, 该时期泥河湾盆地受全球气候变冷影响, 植被以针叶林为主, 生物量较大, 气候波动频繁, 野火活动强; 6)强度大-频率高的火活动模式通常出现在气候转型期或古地磁漂移事件期间, 在2.60~2.56 Ma、2.15~2.14 Ma以及1.82~1.78 Ma出现的火强度和火频率峰值分别对应于Matuyama/Gauss古地磁倒转时期、Reunion正极性漂移事件以及Olduvai正极性漂移事件中后期, 可能与古地磁倒转引起的气候波动变化导致泥河湾盆地野火活动增强有关。

     

应用"天然冷"维护寒区环境

The changes of frozen ground caused by the rising temperature will destroy the heat balance of frozen ground and then damage the roadbeds and foundations in cold area. It is a new idea to collect and store the "natural cold" as a resource and apply it to keep the frozen ground frozen permanently and regulate the summer temperature in cities. This paper introduces the principles and systems used in collecting, storing and transmitting the natural cold , analyses the techniques which keep the frozen ground unchanged and protect the roadbed. The paper also studies the systems and techniques by which the natural cold is used for temperature regulation in cities. And the theories involved in this subject and the prospect of industrializing those techniques are presented as well by the author.     

Gaps in cubic closest packing: from MgO via spinel to the pharmacosiderite crystal structure type

Numerous ordered defect structures are known that are related to the sodium chloride (or MgO) structure type, thus they are basically cubic closest packed (ccp) arrangements with vacancies. For example the NbO type is an MgO type in which one quarter each of the anions and the cations are missing compared to the ccp in such a way that both anions and cations are in square-planar coordination. In spinel, Al₂MgO₄, one half of the octahedrally coordinated cations are missing compared with the MgO type and only one eighth of the tetrahedrally coordinated sites within the ccp are occupied. What these cases have in common is that all these derivatives are rather dense. This is different in pharmacosiderite, K[Fe₄(OH)₄As₃O₁₂]. 6 to 7H₂O, where one half of the anion positions, three quarters of the octahedral sites and five eighth of the tetrahedral sites remain vacant, compared to the spinel type. Pharmacosiderite is a wide open porous structure with zeolitic properties. We are illustrating these relationships using a Bärnighausen symmetry tree and by tables relating the various structure types to each other.     

中国近2000年来气候变化石笋记录研究进展

哥本哈根气候大会的召开,使得近2 000年来的气候变化研究倍受关注。本文对气候变化石笋记录,尤其是我国近2 000年来气候变化石笋记录取得的主要成果进行了总结。已有研究的进展主要在于:发现在中国季风区石笋记录中存在近2 000年来的一系列气候事件,并对其进行了高分辨率重建;对地区热月温度进行了年分辨率的重建,以及通过集成研究发现了"环流效应"等等。但以往的研究仍存在石笋古环境代用指标机理、年代学以及区域代表性石笋记录研究不够等问题。为此,文中提出了加强年际分辨率氧同位素古环境机理,特别是大气降水到石笋的一整套迁移变化过程的研究,以及与其他古环境代用指标的响应机理进行综合研究,加强近2 000年来石笋年代学研究和加强区域性代表性石笋记录研究等建议。     

Vegetation and climate history in the Westeifel Volcanic Field (Germany) during the past 11 000 years based on annually laminated lacustrine maar sediments

Lakes Holzmaar and Meerfelder Maar are located in the Westeifel Volcanic Field less than 10 km apart. Both maar lakes are well known for their annually laminated (varved) sediments covering the past 15 000 years. Here, we focus on reconstructing the history of Holocene vegetation, human impact and climate using high-resolution pollen data. Detailed correlation between the two records using palynologically defined tie-points provides for the first time a test of the precision of the individual varve chronologies. The high-resolution pollen records of both Holzmaar and Meerfelder Maar show continuous natural successions of vegetation during the early and mid-Holocene controlled by the development of soil, climate, immigration and competitive expansion of thermophilous tree species. From 6500 varve yr BP onwards, human impact became an increasingly more important factor. Given the high chronological precision of both records, regional similarities, but also local differences of anthropogenically influenced vegetation changes, can be recognized. The reconstructed July temperature between 8500 and 5000 varve yr BP is around 1 °C higher than today, most likely in response to higher summer insolation related to orbital forcing. High variability of reconstructed July and January temperatures as well as annual precipitation around 5000 varve yr BP is a prominent climatic signal. This is consistent with other records in several areas of Europe which also identify this period as climatically highly variable.     

CO2-forced climate thresholds during the Phanerozoic

The correspondence between atmospheric CO₂ concentrations and globally averaged surface temperatures in the recent past suggests that this coupling may be of great antiquity. Here, I compare 490 published proxy records of CO₂ spanning the Ordovician to Neogene with records of global cool events to evaluate the strength of CO₂-temperature coupling over the Phanerozoic (last 542 my). For periods with sufficient CO₂ coverage, all cool events are associated with CO₂ levels below 1000 ppm. A CO₂ threshold of below ∼500 ppm is suggested for the initiation of widespread, continental glaciations, although this threshold was likely higher during the Paleozoic due to a lower solar luminosity at that time. Also, based on data from the Jurassic and Cretaceous, a CO₂ threshold of below ∼1000 ppm is proposed for the initiation of cool non-glacial conditions. A pervasive, tight correlation between CO₂ and temperature is found both at coarse (10 my timescales) and fine resolutions up to the temporal limits of the data set (million-year timescales), indicating that CO₂, operating in combination with many other factors such as solar luminosity and paleogeography, has imparted strong control over global temperatures for much of the Phanerozoic.     

Vegetation and climate during the last glacial maximum in Japan

The Japanese Archipelago was almost entirely covered by coniferous forests during the last glacial maximum. Northern Hokkaido was distinguished by coniferous parkland and tundra vegetation, while southern Hokkaido and northernmost Honshu were covered by northern boreal coniferous forests consisting mainly of Picea jezoensis, Picea glehnii, Abies sachalinensis, and Larix gmelinii; Tsuga was missing from the forest. More diverse boreal forests including species from Sakhalin and northern Japan grew together in northeastern Honshu. Central Honshu and the mountains of southwestern Japan supported subalpine coniferous forests which are now mainly restricted in distribution to the central mountains. Temperate coniferous forests (Picea polita, Abies firma, and Tsuga sieboldii) existed principally in the modern mid-temperate and evergreen laurel-oak forest regions. Haploxylon pine and tree birch were also abundant in the boreal and cool-temperate zones, as was Diploxylon in the southern temperate zone. Significant populations of Fagus were found along the Pacific coasts of Kyushu and Shikoku, but they were too small to be defined as a beech forest zone. Quercetum mixtum (Quercus, Ulmus, and Tilia) was more common in the coastal lowlands of southwestern Japan than those of northeastern Honshu; it was completely eliminated from Hokkaido. The reduced mean August temperature inferred from the floral assemblages showed a latitudinal gradient 20,000 yr ago; it was 8–9°C in northern Hokkaido, 7.7–8.7°C in northernmost Honshu, 7.2–8.4°C in the central mountains, 6.5°C in the Chugoku District, and 5–6°C in Kyushu. The probable annual precipitation ranged from 1050 to 1300 mm along coasts in southwestern Japan during the culmination of the last glaciation.