Variability of the Bering Sea circulation in the period 1992–2010

Sea surface height anomalies observed by satellites in 1992–2010 are combined with monthly climatologies of temperature and salinity to estimate circulation in the southern Bering Sea. The estimated surface and deep currents are consistent with independent velocity observations by surface drifters and Argo floats parked at 1,000?m. Analysis reveals 1–3-Sv interannual transport variations of the major currents with typical intra-annual variability of 3–7?Sv. On the seasonal scale, the Alaskan Stream transport is well correlated with the Kamchatka (0.81), Near Strait (0.53) and the Bering Slope (0.37) currents. Lagged correlations reveal a gradual increase of the time the lags between the transports of the Alaskan Stream, the Bering Slope Current and the Kamchatka Current, supporting the concept that the Bering Sea basin is ventilated by the waters carried by the Alaskan Stream south of the Aleutian Arc and by the flow through the Near Strait. Correlations of the Bering Sea currents with the Bering Strait transport are dominated by the seasonal cycle. On the interannual time scale, significant negative correlations are diagnosed between the Near Strait transport and the Bering Slope and Alaskan Stream currents. Substantial correlations are also diagnosed between the eddy kinetic energy and Pacific Decadal Oscillation.     

Modelling fish trade liberalisation: Does fish trade liberalisation result in welfare gains or losses?

Recent research has on the basis of general equilibrium models warned that trade liberalisation in non-optimally managed renewable resources might cause over-exploitation and reduced steady-state welfare. Welfare effects of trade liberalisation in open access and optimal management are found case specific and dependent on factors such as the country's status as importer or exporter, the state of the fish stocks and the size of the countries on the world market. The present paper develops an alternative partial equilibrium framework capable of identifying welfare effects of fish trade liberalisation also in the presence of complex but realistic management schemes, such as regulated open access and regulated restricted access. The case dependency known from the general equilibrium analysis is confirmed, but the introduction of realistic fisheries management schemes in the partial equilibrium model extended this case dependency. The welfare effect of trade liberalisation in an exporter country is negative under open access, but was found positive under regulated restricted access in the present paper.     

Incremental melting in the ureilite parent body: Initial composition,melting temperatures,and melt compositions

Ureilites are carbon‐rich ultramafic achondrites that have been heated above the silicate solidus, do not contain plagioclase, and represent the melting residues of an unknown planetesimal (i.e., the ureilite parent body, UPB). Melting residues identical to pigeonite‐olivine ureilites (representing 80% of ureilites) have been produced in batch melting experiments of chondritic materials not depleted in alkali elements relative to the Sun’s photosphere (e.g., CI, H, LL chondrites), but only in a relatively narrow range of temperature (1120 ºC–1180 ºC). However, many ureilites are thought to have formed at higher temperature (1200 ºC–1280 ºC). New experiments, described in this study, show that pigeonite can persist at higher temperature (up to 1280 ºC) when CI and LL chondrites are melted incrementally and while partial melts are progressively extracted. The melt productivity decreases dramatically after the exhaustion of plagioclase with only 5–9 wt% melt being generated between 1120 ºC and 1280 ºC. The relative proportion of pyroxene and olivine in experiments is compared to 12 ureilites, analyzed for this study, together with ureilites described in the literature to constrain the initial Mg/Si ratio of the UPB (0.98–1.05). Experiments are also used to develop a new thermometer based on the partitioning of Cr between olivine and low‐Ca pyroxene that is applicable to all ureilites. The equilibration temperature of ureilites increases with decreasing Al₂O₃ and Wo contents of pyroxene and decreasing bulk REE concentrations. The UPB melted incrementally, at different fO₂, and did not cool significantly (0 ºC–30 ºC) prior to its disruption. It remained isotopically heterogenous, but the initial concentration of major elements (SiO₂, MgO, CaO, Al₂O₃, alkali elements) was similar in the different mantle reservoirs.     

TTG-type plutonic rocks formed in a modern arc batholith by hydrous fractionation in the lower arc crust

We present the geochemistry and intrusion pressures of granitoids from the Kohistan batholith, which represents, together with the intruded volcanic and sedimentary units, the middle and upper arc crust of the Kohistan paleo-island arc. Based on Al-in-hornblende barometry, the batholith records intrusion pressures from ~0.2 GPa in the north (where the volcano-sedimentary cover is intruded) to max. ~0.9 GPa in the southeast. The Al-in-hornblende barometry demonstrates that the Kohistan batholith represents a complete cross section across an arc batholith, reaching from the top at ~8–9 km depth (north) to its bottom at 25–35 km (south-central to southeast). Despite the complete outcropping and accessibility of the entire batholith, there is no observable compositional stratification across the batholith. The geochemical characteristics of the granitoids define three groups. Group 1 is characterized by strongly enriched incompatible elements and unfractionated middle rare earth elements (MREE)/heavy rare earth element patterns (HREE); Group 2 has enriched incompatible element concentrations similar to Group 1 but strongly fractionated MREE/HREE. Group 3 is characterized by only a limited incompatible element enrichment and unfractionated MREE/HREE. The origin of the different groups can be modeled through a relatively hydrous (Group 1 and 2) and of a less hydrous (Group 3) fractional crystallization line from a primitive basaltic parent at different pressures. Appropriate mafic/ultramafic cumulates that explain the chemical characteristics of each group are preserved at the base of the arc. The Kohistan batholith strengthens the conclusion that hydrous fractionation is the most important mechanism to form volumetrically significant amounts of granitoids in arcs. The Kohistan Group 2 granitoids have essentially identical trace element characteristics as Archean tonalite–trondhjemite–granodiorite (TTG) suites. Based on these observations, it is most likely that similar to the Group 2 rocks in the Kohistan arc, TTG gneisses were to a large part formed by hydrous high-pressure differentiation of primitive arc magmas in subduction zones.     

The oxidation state of Ti in hornblende and biotite determined by electron energy-loss spectroscopy,with inferences regarding the Ti substitution

Structural formulae of many Ti-rich hornblendes and biotites exhibit cation deficiencies that increase with Ti content. These deficiencies may be caused by the presence of trivalent instead of tetravalent Ti, of oxygen replacing hydroxyl, or of vacancies on octahedral cation sites. In order to determine the oxidation state of their Ti, electron energy-loss spectra of natural, Ti-rich hornblende and biotites are compared with spectra of natural and synthetic Ti-bearing oxides and silicates. Spectra of Ti₂O₃ and TiO₂ demonstrate that the Ti L _2,3 edge for Ti³⁺ is shifted by ca. 2 eV to lower energy relative to the edge for Ti⁴⁺. Oxidation states of Ti determined by energy-loss spectroscopy for several minerals agree with data from other techniques: tetravalent for Ti-omphacite, perovskite, ilmenite and titanite; trivalent for NaTi³⁺Si₂O₆ pyroxene and fassaite from the Allende meteorite. The energy-loss spectra of the hornblende and biotite show that their Ti is tetravalent and cannot be the cause of the cation deficiencies. The relations between Ti contents and the number of deficiencies differ for hornblende and biotite. Hornblende shows a 2:1 relation between Ti content and deficiencies, suggesting Ti is coupled to an oxygen that is replacing hydroxyl (Ti-oxyhornblende substitution). Biotite shows a 1:1 relation, consistent with coupling of Ti to a vacant octahedral cation site (Ti-vacancy substitution) or to a variable combination of such vacancies and two oxygens replacing hydroxyls (Ti-oxybiotite substitution).     

气候变暖条件下,中(高)亚洲地区不稳定型冻土的巨大挑战和创新解决方案:——来自首届亚洲冻土大会及会后青藏高原考察的总结报告

首届亚洲冻土大会于2006年8月5~16日在兰州、青藏线和拉萨顺利召开.大会讨论主要包括以下5个议题:1)冻土工程;2)山区和高原冻融灾害及冰缘环境;3)冰冻圈的气候与环境条件;4)冻土水文、寒区水资源及土地利用,和;5)冻土监测、制图及模拟.国内论文大多集中于青藏铁路各种科技创新和工程(示范)建设方面.中亚冻土分类、制图和监测研讨会明确了制定统一的中亚地区冻土图的计划和实施方案.会议期间,国内主要新闻媒体对全球15位著名冻土学家进行了联合采访.大约80位中外代表参加了青藏(公)铁路沿线考察,并于8月15日在拉萨举行青藏铁路工程和环境问题讨论会.专家一致认为,青藏铁路所采取的冻土工程措施基本上是恰当、有效的,能够保证青藏铁路路基的长期稳定性.但是,沿线寒区环境保护问题还任重道远,需要尽快进行综合管(治)理,以达到青藏地区社会经济和谐、持续发展的目标.     

An assessment of the ENSO forecast skill of GEOS-5 system

The seasonal forecast skill of the NASA Global Modeling and Assimilation Office atmosphere–ocean coupled global climate model (AOGCM) is evaluated based on an ensemble of 9-month lead forecasts for the period 1993 to 2010. The results from the current version (V2) of the AOGCM consisting of the GEOS-5 AGCM coupled to the MOM4 ocean model are compared with those from an earlier version (V1) in which the AGCM (the NSIPP model) was coupled to the Poseidon Ocean Model. It was found that the correlation skill of the Sea Surface Temperature (SST) forecasts is generally better in V2, especially over the sub-tropical and tropical central and eastern Pacific, Atlantic, and Indian Ocean. Furthermore, the improvement in skill in V2 mainly comes from better forecasts of the developing phase of ENSO from boreal spring to summer. The skill of ENSO forecasts initiated during the boreal winter season, however, shows no improvement in terms of correlation skill, and is in fact slightly worse in terms of root mean square error (RMSE). The degradation of skill is found to be due to an excessive ENSO amplitude. For V1, the ENSO amplitude is too strong in forecasts starting in boreal spring and summer, which causes large RMSE in the forecast. For V2, the ENSO amplitude is slightly stronger than that in observations and V1 for forecasts starting in boreal winter season. An analysis of the terms in the SST tendency equation, shows that this is mainly due to an excessive zonal advective feedback. In addition, V2 forecasts that are initiated during boreal winter season, exhibit a slower phase transition of El Nino, which is consistent with larger amplitude of ENSO after the ENSO peak season. It is found that this is due to weak discharge of equatorial Warm Water Volume (WWV). In both observations and V1, the discharge of equatorial WWV leads the equatorial geostrophic easterly current so as to damp the El Nino starting in January. This process is delayed by about 2 months in V2 due to the slower phase transition of the equatorial zonal current from westerly to easterly.     

Supernova remnants, planetary nebulae and the distance to NGC 4214

We present narrow band, continuum subtracted Hα, [S ii], Hβ, [O iii] and [O ii] data taken with the Wide Field Camera 3 on the Hubble Space Telescope in the nearby dwarf starburst galaxy NGC 4214. From these images, we identify seventeen new planetary nebula candidates, and seven supernova remnant candidates. We use the observed emission line luminosity function of the planetary nebulae to establish a new velocity-independent distance to NGC 4214. We conclude that the PNLF technique gives a reddening independent distance to NGC 4214 of 3.19±0.36 Mpc, and that our current best-estimate of the distance to this galaxy ids 2.98±0.13 Mpc.     

Insight to Ecosystem Based Approach (EBA) at Landscape Level Using a Geospatial Medium

Ecosystem based approach (EBA) for resource management is a concerted, environmentally tuned and an integrated framework that holistically addresses the ecological character of the natural resource, its societal benefit spectrum and its environmental functions. In this paper, the EBA concept is closely linked with the emerging concept of multiple use systems (MUS) while taking account of environmental, economic, and social factors that govern the ecosystems services and benefits. We elucidate a multi-scalar approach and multiple case studies to understand EBA particularly in context of a wetlandscape. At the global scale, Ramsar sites of international importance are geospatially analyzed with reference to their agro-ecology and biodiversity. At regional scale, the agrarian use of inland wetlands in India was re-evaluated taking account of database from a recent inland wetland inventory. At the local scale, drawing on the landscape characterization and the ecological economics for fresh water Lake Kolleru in India and the Muthurajawela Marsh-Negombo Lagoon coastal marsh in Sri Lanka, we illustrate some of the practical challenges in balancing wetland conservation, development needs and the overall well-being of local people. We also discuss how variability in the scale, geophysical characteristics of the site and the data availability confines the ability to simplify a single complete approach to address issues in complex ecosystem such as wetlands. All levels of the study are supported by a variety of earth observation data and the geographical information system (GIS) tools. The site level analysis also draws on socio-economic assessment tools.