典型气候事件对北极渔业资源的影响

随着北极海冰融化加剧,越来越多的渔船涌入北极海域,促使北极渔业资源得到了更好的开发。在这种情况下,研究气候事件对北极海域的影响变得至关重要。本文选取了北大西洋多年代际涛动（Atlantic Multidecadal Oscillation,AMO）、北极涛动（Arctic Oscillation,AO）和北大西洋涛动（North Atlantic Oscillation,NAO） 这三种典型气候事件,通过超前滞后相关、回归分析等统计方法,探究它们与北极渔区 （以27渔区为代表） 渔业总捕捞量以及4种主要经济鱼种 （大西洋鳕、大西洋鲱、格陵兰大比目鱼和大西洋鲑） 捕捞量之间的联系。研究结果表明：1950－2020年,27渔区的海洋渔业总捕捞量总体呈现出两次上升与两次下降过程;在AMO及AO两种气候事件中,AMO对27渔区的捕捞量影响最为显著,同时海冰范围变化对捕捞资源同期影响很强;其中的1980－2020年,4种主要经济鱼种捕捞量与AO相关性均较低,而与AMO呈现明显正或负相关性;4种主要经济鱼种捕捞量与大西洋海表温度存在显著相关性,尤其是类AMO型的海温变化对这4种鱼种捕捞量波动可能存在显著影响。本研究不仅揭示了气候变化对北极渔业资源的显著影响,还根据研究结果提出相应的对策建议,为进一步研究提供了方向和参考,以期实现北极渔业资源可持续发展。     

Deciphering late Devonian–early Carboniferous P–T–t path of mylonitized garnet-mica schists from Prins Karls Forland,Svalbard

Quartz-in-garnet inclusion barometry integrated with trace element thermometry and calculated phase relations is applied to mylonitized schists of the Pinkie unit cropping out on the island of Prins Karls Forland, western part of the Svalbard Archipelago. This approach combines conventional and novel techniques and allows deciphering of the pressure–temperature (P–T) evolution of mylonitic rocks, for which the P–T conditions could not have been easily deciphered using traditional methods. The results obtained suggest that rocks of the Pinkie unit were metamorphosed under amphibolite facies conditions at 8–10 kbar and 560–630°C and mylonitized at ~500 to 550°C and 9–11 kbar. The P–T results are coupled with in-situ Th–U-total Pb monazite dating, which records amphibolite facies metamorphism at c. 359–355 Ma. This is the very first evidence of late Devonian–early Carboniferous metamorphism in Svalbard and it implies that the Ellesmerian Orogeny on Svalbard was associated with metamorphism up to amphibolite facies conditions. Thus, it can be concluded that the Ellesmerian collision between the Franklinian margin of Laurentia and Pearya and Svalbard caused not only commonly accepted brittle deformation and weak greenschist facies metamorphism, but also a burial and deformation of rock complexes at much greater depths at elevated temperatures.     

Water source dynamics of high Arctic river basins

Arctic river basins are amongst the most vulnerable to climate change. However, there is currently limited knowledge of the hydrological processes that govern flow dynamics in Arctic river basins. We address this research gap using natural hydrochemical and isotopic tracers to identify water sources that contributed to runoff in river basins spanning a gradient of glacierization (0–61%) in Svalbard during summer 2010 and 2011. Spatially distinct hydrological processes operating over diurnal, weekly and seasonal timescales were characterized by river hydrochemistry and isotopic composition. Two conceptual water sources (‘meltwater’ and ‘groundwater’) were identified and used as a basis for end‐member mixing analyses to assess seasonal and year‐to‐year variability in water source dynamics. In glacier‐fed rivers, meltwater dominated flows at all sites (typically >80%) with the highest contributions observed at the beginning of each study period in early July when snow cover was most extensive. Rivers in non‐glacierized basins were sourced initially from snowmelt but became increasingly dependent on groundwater inputs (up to 100% of total flow volume) by late summer. These hydrological changes were attributed to the depletion of snowpacks and enhanced soil water storage capacity as the active layer expanded throughout each melt season. These findings provide insight into the processes that underpin water source dynamics in Arctic river systems and potential future changes in Arctic hydrology that might be expected under a changing climate. Copyright © 2013 John Wiley & Sons, Ltd.     

Rainfall–runoff responses on Arctic hillslopes underlain by continuous permafrost,North Slope,Alaska, USA

The Arctic hydrologic cycle is intensifying, as evidenced by increased rates of precipitation, evapotranspiration, and riverine discharge. However, the controls on water fluxes from terrestrial to aquatic systems in upland Arctic landscapes are poorly understood. Upland landscapes account for one third of the Arctic land surface and are often drained by zero‐order geomorphic flowpath features called water tracks. Previous work in the region attributed rapid runoff response at larger stream orders to water tracks, but models suggest water tracks are hydrologically disconnected from the surrounding hillslope. To better understand the role of water tracks in upland landscapes, we investigated the surface and subsurface hydrologic responses of 6 water tracks and their hillslope watersheds to natural patterns of rainfall, soil thaw, and drainage. Between storms, both water track discharge and the water table in the hillslope watersheds exhibited diel fluctuations that, when lagged by 5 hr, were temporally correlated with peak evapotranspiration rate. Water track soils remained saturated for more of the summer season than soils in their surrounding hillslope watersheds. When rainfall occurred, the subsurface response was nearly instantaneous, but the water tracks took significantly longer than the hillslopes to respond to rainfall, and longer than the responses previously observed in nearby larger order Arctic streams. There was also evidence for antecedent soil water storage conditions controlling the magnitude of runoff response. Based on these observations, we used a broken stick model to test the hypothesis that runoff production in response to individual storms was primarily controlled by rainfall amount and antecedent water storage conditions near the water track outlet. We found that the relative importance of the two factors varied by site, and that water tracks with similar watershed geometries and at similar landscape positions had similar rainfall–runoff model relationships. Thus, the response of terrestrial water fluxes in the upland Arctic to climate change depends on the non‐linear interactions between rainfall patterns and subsurface water storage capacity on hillslopes. Predicting these interactions across the landscape remains an important challenge.     

An examination of snow redistribution over smooth land‐fast sea ice

An understanding of temporal evolution of snow on sea ice at different spatial scales is essential for improvement of snow parameterization in sea ice models. One of the problems we face, however, is that long‐term climate data are routinely available for land and not for sea ice. In this paper, we examine the temporal evolution of snow over smooth land‐fast first‐year sea ice using observational and modelled data. Changes in probability density functions indicate that depositional and drifting events control the evolution of snow distribution. Geostatistical analysis suggests that snowdrifts increased over the study period, and the orientation was related to the meteorological conditions. At the microscale, the temporal evolution of the snowdrifts was a product of infilling in the valleys between drifts. Results using two shore‐based climate reporting stations (Paulatuk and Tuktoyuktuk, NWT) suggest that on‐ice air temperature and relative humidity can be estimated using air temperature recorded at either station. Wind speed, direction and precipitation on ice cannot be accurately estimated using meteorological data from either station. The temporal evolution of snow distribution over smooth land‐fast sea ice was modelled using SnowModel and four different forcing regimes. The results from these model runs indicate a lack of agreement between observed distribution and model outputs. The reasons for these results are lack of meteorological measurements prior to the end of January, lack of spatially adequate surface topography and discrepancies between meteorological variables on land and ice. Copyright © 2009 John Wiley & Sons, Ltd.     

2012/2013年冬季中国气温异常成因分析

2012/2013年冬季,我国平均气温为-3.8℃,较常年同期(-3.4℃)偏低0.4℃,就空间分布来看,我国东北、华北、黄淮、江淮和新疆北部气温较常年同期偏低。利用1951-2013年国家气候中心整理的全国160站月平均气温资料、英国Hadley中心全球海温资料、NCEP/NCAR再分析大气环流资料、德国不莱梅大学提供的海冰卫星遥感资料,通过EOF分析、回归分析、合成分析、相关分析方法研究了引起2012/2013年冬季我国气温异常的东亚中高纬大气环流异常,并从海洋环境要素异常的角度分析造成这种环流异常的原因。分析结果表明:2012/2013年冬季我国气温异常分布主要是由于北极涛动(AO,Arctic Oscillation)呈负位相,西伯利亚地区高度场异常偏高,东亚大槽明显偏深的环流形式引起的。而太平洋年代际振荡(PDO,Pacific Decadal Oscillation)负位相是引起西伯利亚高压强度偏强和东亚冬季风强度偏强的年代际海洋背景,前期9月海冰范围异常偏小是导致2012/2013年冬季AO呈现负位相及我国东北和新疆北部呈现异常低温的主要原因。     

北极秋季海冰密集度与中国初冬降雨之间的关系

本文通过对中国地区实测降水及北极海冰卫星数据的分析,研究了北极秋季海冰密集度与中国初冬降雨的关系。合成分析的研究结果表明2000年之前中国南方和北方冬季降水偏少,中部降水偏多,这之后中国南方和北方冬季降水增加,中部降水减少。SVD研究结果显示,北极海冰减少使得近三十年来中国南方和北方冬季降雨呈现逐渐增多,中部地区(从青藏高原向东北方向至日本)降雨逐步减少的趋势。随着北极海冰的进一步减少,如遇合适的气候条件,南方冻雨出现的概率会加大。北极秋季海冰异常的回复过程加之冬季海冰异常的延续信号在中国、蒙古及日本北部激发一个阻塞高压,以巴伦支海/卡拉海为中心激发一个异常低压。这使得来自北冰洋大西洋扇区的冷空气南下至欧洲大陆和亚洲北部,在阻塞高压的影响下,冷空气进一步南下,进入东亚地区。这不仅使得亚洲冬季温度降低,也为中国北部降水增加提供条件。     

冰上丝绸之路与北极油气资源

油气是重要的战略资源。其中天然气作为清洁能源,它曾经是,现在是,在可预期的未来——全球碳减排、中国碳达峰情景下,仍然是最重要的能源资源。能源进口渠道的多元化一直是中国缓解能源紧张的有效措施之一。北极地区油气资源丰富且以天然气为主,已发现的油气资源中绝大多数在俄罗斯,尤其是天然气。但是俄罗斯天然气生产的油气田80%以上已经进入北极圈。2012年,中俄合作开发北极亚马尔液化天然气项目正式启动,标志着中国参与北极油气资源开发利用取得重要进展,也事实上开启了中国主导的"丝绸之路经济带建设"和俄罗斯主导的"欧亚经济联盟建设"对接合作的进程。北极地区已发现的油气资源共计3289.4亿桶油当量,其中石油605.4亿桶（84.1亿吨）油当量,仅为全球已发现石油资源的2.5%;天然气41.4万亿立方米（约合2683亿桶,372.6亿吨油当量）,占全球已发现天然气资源的15.5%。北极地区已发现的油气总资源中绝大多数在俄罗斯,俄罗斯已发现的北极油气资源合计2905亿桶油当量（403.5亿吨）,占88.3%;其中天然气约39.47万亿立方米,约合2557.9亿桶（355.3亿吨）油当量,占北极地区已发现天然气总资源的95%以上。北极待发现的油气资源量也非常可观,约占世界待发现常规石油资源的15%;天然气占世界待发现常规天然气资源的30%,其分布也主要在俄罗斯。随着全球气候变暖和能源战略博弈,俄罗斯为确保其天然气出口及财政来源,必然要加大北极油气、特别是天然气的开采和开发,并通过北极航道运到中国和其他消费国。本文在概括分析北极油气资源分布特点、俄罗斯油气资源与北极战略及北方海航道通行能力的基础上,回顾了北极亚马尔液化天然气项目诞生、发展演变及其国际博弈的背景;概括介绍了中国成功介入北极油气资源项目这一标志性事件过程,并进一步提出了中国对北极油气资源利用战略举措的建议。      

Polar WRF模式海冰密集度方案对北极海雾模拟效果的个例研究

全球变暖的背景下,北极航线的常规通航甚至商业运营有望实现,而海雾会严重影响航道上船只的航行安全。海冰的存在使海气之间相互作用变得更为复杂,是研究北极海雾不可忽略的因素。船载观测发现,与中纬度常见平流冷却雾形成时气温下降速度往往超过海水降温速度不同,北极海雾发生时海冰的存在还会使海水降温速度超过空气降温速度。然而目前海冰分布是否会影响模式模拟海雾的准确性还不得而知,因此本文利用Polar WRF（Polar Weather Research and Forecasting）模式模拟了中国第七次北极考察中观测到的一次海雾过程,并进行海冰密集度敏感性试验。通过与船载观测和欧洲中期天气预报中心再分析数据比对发现,在低浮冰区内（海冰密集度小于50%）考虑海冰分布时可以更加准确地刻画潜热通量与水汽通量,模拟出与观测事实相符的表层空气降温与增湿过程以及相对湿度的变化,因此能够更好地刻画海雾的三维结构及其生消演变。