Sensitivity of modern climate to the presence,strength and salinity of Mediterranean-Atlantic exchange in a global general circulation model     

Ruza F. Ivanovic  Paul J. Valdes  Lauren Gregoire  Rachel Flecker  Marcus Gutjahr 《Climate Dynamics》2014,42(3-4):859-877

Mediterranean Outflow Water (MOW) is thought to be a key contributor to the strength and stability of Atlantic Meridional Overturning Circulation (AMOC), but the future of Mediterranean-Atlantic water exchange is uncertain. It is chiefly dependent on the difference between Mediterranean and Atlantic temperature and salinity characteristics, and as a semi-enclosed basin, the Mediterranean is particularly vulnerable to future changes in climate and water usage. Certainly, there is strong geologic evidence that the Mediterranean underwent dramatic salinity and sea-level fluctuations in the past. Here, we use a fully coupled atmosphere–ocean General Circulation Model to examine the impact of changes in Mediterranean-Atlantic exchange on global ocean circulation and climate. Our results suggest that MOW strengthens and possibly stabilises the AMOC not through any contribution towards NADW formation, but by delivering relatively warm, saline water to southbound Atlantic currents below 800 m. However, we find almost no climate signal associated with changes in Mediterranean-Atlantic flow strength. Mediterranean salinity, on the other hand, controls MOW buoyancy in the Atlantic and therefore affects its interaction with the shallow-intermediate circulation patterns that govern surface climate. Changing Mediterranean salinity by a factor of two reorganises shallow North Atlantic circulation, resulting in regional climate anomalies in the North Atlantic, Labrador and Greenland-Iceland-Norwegian Seas of ±4 °C or more. Although such major variations in salinity are believed to have occurred in the past, they are unlikely to occur in the near future. However, our work does suggest that changes in the Mediterranean’s hydrological balance can impact global-scale climate.  相似文献   

A one-dimensional modeling study of the diurnal cycle in the equatorial Atlantic at the PIRATA buoys during the EGEE-3 campaign     

Malick Wade  Guy Caniaux  Yves duPenhoat  Marcus Dengler  Hervé Giordani  Rebecca Hummels 《Ocean Dynamics》2011,61(1):1-20

A one-dimensional model is used to analyze, at the local scale, the response of the equatorial Atlantic Ocean under different meteorological conditions. The study was performed at the location of three moored buoys of the Pilot Research Moored Array in the Tropical Atlantic located at 10° W, 0° N; 10° W, 6° S; and 10° W, 10° S. During the EGEE-3 (Etude de la circulation océanique et de sa variabilité dans le Golfe de Guinee) campaign of May–June 2006, each buoy was visited for maintenance during 2 days. On board the ship, high-resolution atmospheric parameters were collected, as were profiles of temperature, salinity, and current. These data are used here to initialize, force, and validate a one-dimensional model in order to study the diurnal oceanic mixed-layer variability. It is shown that the diurnal variability of the sea surface temperatures is mainly driven by the solar heat flux. The diurnal response of the near-surface temperatures to daytime heating and nighttime cooling has an amplitude of a few tenths of degree. The computed diurnal heat budget experiences a net warming tendency of 31 and 27 W m⁻² at 0° N and 10° S, respectively, and a cooling tendency of 122 W m⁻² at 6° S. Both observed and simulated mixed-layer depths experience a jump between the nighttime convection phase and the well-stabilized diurnal water column. Its amplitude changes dramatically depending on the meteorological conditions occurring at the stations and reaches its maximum amplitude (~50 m) at 10° S. At 6° and 10° S, the presence of barrier layers is observed, a feature that is clearer at 10° S. Simulated turbulent kinetic energy (TKE) dissipation rates, compared to independent microstructure measurements, show that the model tracks their diurnal evolution reasonably well. It is also shown that the shear and buoyancy productions and the vertical diffusion of TKE all contribute to the supply of TKE, but the buoyancy production is the main source of TKE during the period of the simulation.  相似文献   

Factors controlling the distribution of anaerobic methanotrophic communities in marine environments: Evidence from intact polar membrane lipids     

Pamela E. Rossel  Marcus Elvert  Antje Boetius 《Geochimica et cosmochimica acta》2011,75(1):164-3574

Three distinct types of microbial consortia appear to mediate the anaerobic oxidation of methane with sulfate as electron acceptor in marine sediments and are distributed ubiquitously. These consortia consist of ANerobic MEthanotrophic (ANME) archaea of the ANME-1, ANME-2 and ANME-3 clades and their sulfate-reducing bacterial partners either of the Desulfosarcina-Desulfococcus (ANME-1/DSS and ANME-2/DSS) or Desulfobulbus spp. (ANME-3/DBB) branches. Frequently one consortium type dominates the community, but the selective factors are not well constrained. Here we analyzed patterns in the composition of intact polar lipids extracted from bacterial and archaeal communities of different marine seep environments. Further, we investigated if different environmental and geographical factors were responsible for the observed patterns, and hence could be important in the selection of seep communities. Intact polar lipids (IPLs) provide a more robust distinction of the composition of extant communities than their less polar derivatives. In ANME-1/DSS-dominated communities, glycosidic- and phospho-glyceroldialkylglyceroltetraethers were abundant, while ANME-2/DSS and ANME-3/DBB-dominated communities showed abundant archaeol-based IPLs, either with glycosidic and phospho-headgroups or only phospho-headgroups, respectively. The relative proportion of bacterial IPLs varied widely from 0% to 93% and was generally lower in samples of the ANME-1 type, suggesting lower bacterial biomasses in the respective communities. In addition to these lipid signatures, distinctive features were related to the habitat characteristics of these communities: lower amounts of phosphate-based IPLs were generally observed in communities from calcified microbial mats compared to sediments, which may reflect phosphate limitation. Based on statistical analyses of IPLs and environmental data this study constrained for the first time the occurrence of three environmental factors controlling the distribution of different ANME-associated communities in a wide range of hydrocarbon seep systems. Habitats dominated by ANME-1/DSS communities were characterized by high temperature and low oxygen content in bottom waters (or even anoxia), while ANME-2/DSS and ANME-3/DBB-dominated sediments were located in settings with lower temperatures and higher oxygen content in bottom waters. Furthermore, ANME-2/DSS communities were particularly prominent in environments in which a relatively high supply of sulfate was sustained.  相似文献   

Realised added value in dynamical downscaling of Australian climate change     

Di Virgilio  Giovanni  Evans  Jason P.  Di Luca  Alejandro  Grose  Michael R.  Round  Vanessa  Thatcher  Marcus 《Climate Dynamics》2020,54(11):4675-4692

Climate Dynamics - Coarse resolution global climate models (GCMs) cannot resolve fine-scale drivers of regional climate, which is the scale where climate adaptation decisions are made. Regional...  相似文献   

Examining the impact of multiple climate forcings on simulated Southern Hemisphere climate variability     

Beraki  Asmerom F.  Morioka  Yushi  Engelbrecht  Francois A.  Nonaka  Masami  Thatcher  Marcus  Kobo  Nomkwezane  Behera  Swadhin 《Climate Dynamics》2020,54(11):4775-4792

Climate Dynamics - The study examines the influence of external climate forcings, and atmosphere–ocean–sea–ice coupled interaction on the Southern Hemisphere (SH) atmospheric...  相似文献   

The importance of health co-benefits in macroeconomic assessments of UK Greenhouse Gas emission reduction strategies     

Henning Tarp Jensen  Marcus R. Keogh-Brown  Richard D. Smith  Zaid Chalabi  Alan D. Dangour  Mike Davies  Phil Edwards  Tara Garnett  Moshe Givoni  Ulla Griffiths  Ian Hamilton  James Jarrett  Ian Roberts  Paul Wilkinson  James Woodcock  Andy Haines 《Climatic change》2013,119(2):223-237

We employ a single-country dynamically-recursive Computable General Equilibrium model to make health-focussed macroeconomic assessments of three contingent UK Greenhouse Gas (GHG) mitigation strategies, designed to achieve 2030 emission targets as suggested by the UK Committee on Climate Change. In contrast to previous assessment studies, our main focus is on health co-benefits additional to those from reduced local air pollution. We employ a conservative cost-effectiveness methodology with a zero net cost threshold. Our urban transport strategy (with cleaner vehicles and increased active travel) brings important health co-benefits and is likely to be strongly cost-effective; our food and agriculture strategy (based on abatement technologies and reduction in livestock production) brings worthwhile health co-benefits, but is unlikely to eliminate net costs unless new technological measures are included; our household energy efficiency strategy is likely to breakeven only over the long term after the investment programme has ceased (beyond our 20 year time horizon). We conclude that UK policy makers will, most likely, have to adopt elements which involve initial net societal costs in order to achieve future emission targets and longer-term benefits from GHG reduction. Cost-effectiveness of GHG strategies is likely to require technological mitigation interventions and/or demand-constraining interventions with important health co-benefits and other efficiency-enhancing policies that promote internalization of externalities. Health co-benefits can play a crucial role in bringing down net costs, but our results also suggest the need for adopting holistic assessment methodologies which give proper consideration to welfare-improving health co-benefits with potentially negative economic repercussions (such as increased longevity).  相似文献   

<Superscript>10</Superscript>Be surface exposure dating of the last deglaciation in the Aare Valley,Switzerland     

Lorenz Wüthrich  Ezequiel Garcia Morabito  Jana Zech  Mareike Trauerstein  Heinz Veit  Christian Gnägi  Silke Merchel  Andreas Scharf  Georg Rugel  Marcus Christl  Roland Zech 《Swiss Journal of Geoscience》2018,111(1-2):295-303

The combined Rhone and Aare Glaciers presumably reached their last glacial maximum (LGM) extent on the Swiss Plateau prior to 24 ka. Two well-preserved, less extensive moraine stades, the Gurten and Bern Stade, document the last deglaciation of the Aare Valley, yet age constraints are very scarce. In order to establish a more robust chronology for the glacial/deglacial history of the Aare Valley, we applied ¹⁰Be surface exposure dating on eleven boulders from the Gurten and Bern Stade. Several exposure ages are of Holocene age and likely document post-depositional processes, including boulder toppling and quarrying. The remaining exposure ages, however yield oldest ages of 20.7 ± 2.2 ka for the Gurten Stade and 19.0 ± 2.0 ka for the Bern Stade. Our results are in good agreement with published chronologies from other sites in the Alps.  相似文献   

Seasonal controls on sediment transport and deposition in Lake Ohau,South Island,New Zealand: Implications for a high‐resolution Holocene palaeoclimate reconstruction          下载免费PDF全文

Heidi A. Roop  Gavin B. Dunbar  Richard Levy  Marcus J. Vandergoes  Alexander L. Forrest  Sharon L. Walker  Jennifer Purdie  Phaedra Upton  James Whinney 《Sedimentology》2015,62(3):826-844

Laminated sediments in Lake Ohau, Mackenzie Basin, New Zealand, offer a potential high‐resolution climate record for the past 17 kyr. Such records are particularly important due to the relative paucity of detailed palaeoclimate data from the Southern Hemisphere mid‐latitudes. This paper presents outcomes of a study of the sedimentation processes of this temperate lake setting. Hydrometeorological, limnological and sedimentological data were collected over a 14 month period between 2011 and 2013. These data indicate that seasonality in the hydrometeorological system in combination with internal lake dynamics drives a distinct seasonal pattern of sediment dispersal and deposition on a basin‐wide scale. Sedimentary layers that accumulate proximal to the lake inflow at the northern end of the lake form in response to discrete inflow events throughout the year and display an event stratigraphy. In contrast, seasonal change in the lake system controls accumulation of light (winter) and dark (summer) laminations at the distal end of the lake, resulting in the preservation of varves. This study documents the key processes influencing sediment deposition throughout Lake Ohau and provides fundamental data for generating a high‐resolution palaeoclimate record from this temperate lake.  相似文献   

Use of principal component analysis for identification of Rockland and Trego Hot Springs tephras in the Hat Creek Graben,northeastern California,USA     

Solène Pouget  Marcus Bursik  Joaquín A. Cortés  Chris Hayward 《Quaternary Research》2014

Discontinuous tephra layers were discovered at Burney Spring Mountain, northern California. Stratigraphic relationships suggest that they are two distinct tephras. Binary plots and standard similarity coefficients of electron probe microanalysis data have been supplemented with principal component analysis to correlate the two tephra layers to known regional tephras. Using principal component analysis, we are furthermore able to bound our uncertainty in the correlation of the two tephra layers. After removal of outliers, within the 95% prediction interval, we can say that one tephra layer is likely the Rockland tephra, aged 565–610 ka, and the second layer is likely from Mt. Mazama, the Trego Hot Springs tephra, aged ~ 29 ka. In the case of the Rockland tephra, the new findings suggest that dispersal to the north was highly restricted. For Trego Hot Springs ash, the new findings extend the distribution to the southwest, with a rapid thinning in that direction. Coupled with considerations of regular tephra dispersal patterns, the results suggest that the primary dispersal direction for both tephras was to the south, and that occurrences in other directions are unlikely or otherwise anomalous.  相似文献   

Rising powers: the evolving role of BASIC countries     

Karl Hallding  Marie Jürisoo  Marcus Carson  Aaron Atteridge 《Climate Policy》2013,13(5):608-631

The exponential growth in global populations, economic activity and resource utilization means it is becoming increasingly difficult to satisfy global demand for a number of fundamental resources, while some key ecosystems services are under stress. The likelihood of future resource scarcities have begun to influence the positions taken within international climate change negotiations by fast-growing developing countries. When Brazil, South Africa, India, and China formed the BASIC group it took many by surprise. The coordination needed to align this heterogeneous group of countries cannot simply be understood in terms of a set of shared interests around climate policy. How the BASIC group emerged and the nature of its cooperation on climate change are examined within the broader context in which these increasingly powerful countries came to join forces. Although traditionally aligned with the G77 group of developing countries, recent strategising as a group of emerging economies reflects their realization that there are insufficient global resources available to follow the same development pathway as industrialized countries. Hence, they must seek alternative growth pathways, which requires establishing common ground while also keeping track of each others' positions on important global issues like climate change.  相似文献