Present warming within the context of cooling–warming cycles observed since 1854 in the Bay of Biscay

The warming trend observed during the last decades in the Bay of Biscay is put within the context of sea surface temperature (SST) changes observed in the area since 1854. Macroscopically, two consecutive warming–cooling cycles were detected during this period of time: cooling from 1867 to 1910; warming from 1910 to 1945; cooling from 1945 to 1974; and warming from 1974 to nowadays. Warming rates of 0.17 and 0.22 °C per decade were measured during the warming sub-periods and cooling rates of ?0.14 and ?0.10 °C per decade were measured during the cooling sub-periods. The present warming period is on the same order of magnitude although slightly more intense than the one observed from 1910 to 1945, which is consistent with previous analysis carried for the North Atlantic. Finally, the thermal amplitude defined as the difference between the maximum and minimum annual values has increased since 1974 at a rate of 0.06 °C per decade due to the different increasing rates of the maximum (0.26 °C per decade) and minimum (0.20 °C per decade) SSTs.     

华北克拉通南缘中条山-嵩山地区1.78Ga基性岩墙群的地球化学特征及构造环境

幔源岩浆侵位产生的基性岩墙群是地壳伸展裂解的重要标志。华北克拉通南缘中条山-嵩山地区出露有大量的中元古代基性岩墙群,对其研究将有助于深入了解华北克拉通中元古代构造演化特征。其岩石类型以辉绿岩为主,少量辉长辉绿岩和辉绿玢岩;主要造岩矿物为斜长石和单斜辉石,其它矿物包括角闪石、Fe-Ti氧化物、磷灰石、黑云母、碱性长石和石英。锆石SHRIMPU-Pb年龄为1785±18Ma,代表岩墙的结晶年龄。岩石K2O+Na2O含量为3.63%～6.18%,K2O/Na2O比值为0.73～1.38,FeOT含量较高(10.03%～13.59%),属于拉斑玄武岩系列。岩石的稀土元素含量高(142×10-6～381×10-6),亏损Nb、Ta、Zr、Hf等高场强元素,富集Rb、Ba、La等大离子亲石元素,全岩εNd(t)值为-6.2～-8.1。岩墙的固结指数(SI)和MgO含量呈明显的正相关关系,说明幔源岩浆发生过明显的结晶分异作用。地球化学分析表明,研究区基性岩墙属于板内拉斑玄武岩系列,与熊耳群火山岩有相似的地球化学特征;基于两者紧密的产出关系,我们认为该区岩墙可能是熊耳群火山岩的通道岩墙,共同代表了华北克拉通东、西陆块碰撞后伸展事件。     

Stable isotope analysis of consumer food webs indicates ecosystem recovery following prolonged drought in a subtropical estuarine lake

Assessing changes in food-web structure provides a useful monitoring tool for gauging the resilience of ecosystems in the face of climatic impacts. We consider the ecological resilience of a large estuarine lake (St Lucia Estuary, South Africa) in the wake of an extreme climatic event (prolonged drought). Using carbon and nitrogen stable isotopes, food-web structure was assessed at five sites across the estuary during the winter and spring of 2013. Sampling occurred approximately three years after heavy rains flooded the system and returned it to a relatively diluted state following an almost decade-long drought that decimated food webs in the upper parts of the estuary due to hypersalinity effects. Comparisons of niche width and variance of consumer food webs among sites revealed a general homogenisation of food webs across the entire system, contrasting with the spatial differentiation of food webs documented during the drought phase. Our results indicate that the estuary is able to maintain ecological resilience at the whole-system level in the face of an extreme drought. This is likely facilitated by source pools of species residing in the relatively stable lower estuary, which are able to rapidly recolonise areas denuded by drought in the upper estuary.     

Coastal and oceanic SST variability along the western Iberian Peninsula

The inter-annual variability of the sea surface temperature (SST) was analyzed along the western Iberian Peninsula in the region ranging from 9.5 °W to 21.5 °W and from 37.5 °N to 42.5 °N with a spatial resolution of 1°×1° from 1900 to 2008. Both coastal and oceanic SST showed an overall increase with warming and cooling cycles similar to those observed in the North Atlantic region and in previous regional studies. In addition, the evolution of coastal and ocean water has been observed to be different. In general, ocean water is more affected by the different warming–cooling cycles than coastal water. In spite of coast and ocean are highly influenced by global changes affecting the whole North Atlantic region, near shore SST has been observed to be correlated with local wind regime, which is itself a manifestation of the Eastern Atlantic (EA) teleconnection pattern.     

Taxonomic level for assessing oil spill effects on soft-bottom sublittoral benthic communities

Infralittoral soft-bottom macrofauna abundance data collected during four-year surveys after the Aegean Sea (Galicia, Spain) and the Amoco Cadiz oil spill (Brittany, France) at a total of seven sites were analysed at three different taxonomic levels (species, genus, and family). The effects of the spills on macrofauna populations were very similar in the two areas. The post-spill time-courses of Shannon-Weaver diversity values were similar regardless of whether species-, genus- or family-level data were used. Non-metric multidimensional scaling identified well-defined groups of samples corresponding to different times post-spill, and again the results obtained were very similar regardless of the taxonomic level considered. In general, the use of genus- or family-level data did not lead to relevant information loss by comparison with species-level data. In view of these findings and those of previous studies of this type, we conclude that family-level data is generally sufficient for monitoring pollution effects in infralittoral soft-bottom environments.     

铜陵狮子山地区中酸性侵入岩锆石SHRIMP U-Pb定年及岩浆作用的深部过程

铜陵狮子山地区中酸性侵入岩锆石SHRIMP U-Pb定年结果表明,白茫山辉石二长闪长岩、鸡冠山和大团山石英二长闪长岩以及胡村花岗闪长岩的年龄分别为:138.21 ±0.82Ma、139.9 ±1.1Ma、139.3 ±1.2Ma和140.9 ±1.2Ma.岩浆侵位顺序为花岗闪长岩→石英二长闪长岩→辉石二长闪长岩.根据锆石SHRIMP U-Pb年龄变化范围,推测该区岩浆活动持续的时间约为15Ma,且岩浆属脉动式多次侵位,后期岩浆侵位的热使早期岩体中已结晶的锆石发生熔解、重结晶,形成新的锆石.地下深部岩浆活动频繁,形成了多级岩浆房,使得本区的莫霍面界线不明显.     

Review of the current distribution of southern elephant seals in the eastern South Pacific

The eastern South Pacific southern elephant seal population was extinguished by extensive hunting and the current presence of this species in this area is not well understood. We reviewed existing records from the 1900s to 2014 in the eastern South Pacific, as well as tagged seals and movement records in order to assess the potential immigration source of these individuals. A total of 409 confirmed sightings were compiled, ranging from the southern tip of South America (Cape Horn Archipelago) as far north as Ecuador, including some oceanic island groups. The evidence shows also that recolonisation of its former Pacific distribution has started, with slow population growth in three incipient pupping sites in southern Chile (south of 51°S). Although the source of all of the individuals in the growing colonies is unknown, evidence from tags and satellite tagging indicates that some seals come from subpopulations on the Peninsula Valdes and the Falkland/Malvinas Islands, although mtDNA analysis showed, preliminarily, a greater genetic relationship only with the Falkland/Malvinas Islands rookery.     

A strategy for frequency spectra of quaternary climate records

The paleoclimatic variability at frequencies ranging from 10^–4 cycle per year (cpy) to 10^–5 cpy is investigated using a set of four deep-sea cores from the Atlantic, Pacific and Indian Oceans. Dominant features are the presence of orbital frequencies corresponding to mean periods of 117.7, 43.6, 24.9 and 19.3 kyr. These are statistically significant according to such advanced spectral tools as Blackman-Tukey, maximum entropy and the highly efficient Thomson technique. However, the main purpose of this paper is methodological, describing the statistical analyses of time series with modern methods in order to stress their relative power, advantages and disadvantages. The more advanced statistical methods confirm the coincidence of the dominant periods in the deep sea cores and those in the astronomical elements, including combination tones. Three frequency bands of high paleoclimatic variability centred at 15.4, 13 and 10.8 kyr are indeed also detected. These two last periods are very close to those predicted by the climatic non-linear model of Ghil and Le Treut and found by Pestiaux et al. and Yiou et al.