Impact of climatic change on the biological production in the Barents Sea

The Barents Sea is a high latitude ecosystem and is an important nursery and feeding area for commercial fish stocks such as cod, capelin and herring. There is a large inter-annual variability both in physical and biological conditions in the Barents Sea. Understanding and predicting changes in the system requires insight into the coupled nature of the physical and biological interactions. A coupled physical and biological ocean model is used to study the impact of postulated future atmospheric changes on the physical and biological conditions in the Barents Sea. Results from this simulation not only show that there is a large variability in the physical conditions on a wide range of time scales, but also that the temperature in the Barents Sea is increasing. The corresponding ice cover decrease is most noticeable in the summer months. The changes in physical properties will most likely have an impact on the biotope. On average, the primary production increases slightly over a 65 year long period, about 8%, partly due to an increased production in the northern Barents Sea. The model further simulates that the production of Atlantic zooplankton species increases approximately 20% and becomes more abundant in the east. The Arctic zooplankton biomass decreases significantly (50%) causing the total simulated production to decrease.     

Ocean heat transport into the Arctic in the twentieth and twenty-first century in EC-Earth

The ocean heat transport into the Arctic and the heat budget of the Barents Sea are analyzed in an ensemble of historical and future climate simulations performed with the global coupled climate model EC-Earth. The zonally integrated northward heat flux in the ocean at 70°N is strongly enhanced and compensates for a reduction of its atmospheric counterpart in the twenty first century. Although an increase in the northward heat transport occurs through all of Fram Strait, Canadian Archipelago, Bering Strait and Barents Sea Opening, it is the latter which dominates the increase in ocean heat transport into the Arctic. Increased temperature of the northward transported Atlantic water masses are the main reason for the enhancement of the ocean heat transport. The natural variability in the heat transport into the Barents Sea is caused to the same extent by variations in temperature and volume transport. Large ocean heat transports lead to reduced ice and higher atmospheric temperature in the Barents Sea area and are related to the positive phase of the North Atlantic Oscillation. The net ocean heat transport into the Barents Sea grows until about year 2050. Thereafter, both heat and volume fluxes out of the Barents Sea through the section between Franz Josef Land and Novaya Zemlya are strongly enhanced and compensate for all further increase in the inflow through the Barents Sea Opening. Most of the heat transported by the ocean into the Barents Sea is passed to the atmosphere and contributes to warming of the atmosphere and Arctic temperature amplification. Latent and sensible heat fluxes are enhanced. Net surface long-wave and solar radiation are enhanced upward and downward, respectively and are almost compensating each other. We find that the changes in the surface heat fluxes are mainly caused by the vanishing sea ice in the twenty first century. The increasing ocean heat transport leads to enhanced bottom ice melt and to an extension of the area with bottom ice melt further northward. However, no indication for a substantial impact of the increased heat transport on ice melt in the Central Arctic is found. Most of the heat that is not passed to the atmosphere in the Barents Sea is stored in the Arctic intermediate layer of Atlantic water, which is increasingly pronounced in the twenty first century.     

The influence of the North Atlantic on climate variations in the Barents Sea and their predictability

The effects of Atlantic water inflow on the climate variability in the Barents Sea are studied. Initial data are the series of water temperature at the Kola meridian cross-section, monthly values of ice extent, air temperature at the stations, sea level pressure from the reanalysis data, and sea surface temperature. The methods of multivariate correlation, spectral, and factor analysis and EOF decomposition are used. It was found that variations in the Atlantic water inflow define the main part of interannual variability of sea ice extent, water temperature, and air temperature in the Barents Sea in the cold season. The influence of regional atmospheric circulation on the interannual variability of these parameters is small. The effects that water temperature anomalies in the area of Newfoundland and in the equatorial part of the North Atlantic have on climate parameters in the Barents Sea are discovered. The response of these parameters lags behind the respective anomalies by 9-58 months. The high correlation between them makes it possible to develop the method of statistical forecasting of sea ice extent and water temperature in the Barents Sea with the lead time up to 4 years.     

Capelin migrations and climate change – a modelling analysis

The capelin is a small pelagic fish that performs long distance migrations. It is a key species in the Barents Sea ecosystem and its distribution is highly climate dependent. Here we use an individual based model to investigate consequences of global warming on capelin distribution and population dynamics. The model relies on input on physics and plankton from a biophysical ocean model, and the entire life cycle of capelin including spawning of eggs, larval drift and adult movement is simulated. Spawning day and adult movement strategies are adapted by a genetic algorithm. Spawning has to take place in designated near-shore spawning areas. The output generated by the model is capelin migration/distribution and population dynamics. We present simulations with present day climate and a future climate scenario. For the present climate the model evolves a spatial distribution resembling typical spatial dynamics of capelin with the coasts of Northern Norway and Murman as the main spawning areas. For the climate change simulation, the capelin is predicted to shift spawning eastwards and also utilize new spawning areas along Novaya Zemlya. There is also a shift in the adult distribution towards the north eastern part of the Barents Sea and earlier spawning associated with the warming.     

Climatic variations of ice conditions in different regions of the Barents Sea

Presented are the results of studying the regional peculiarities of climatic variations of spatiotemporal distribution of ice in the Barents Sea water area in 1977?C2010. Demonstrated is the dynamics of the interannual and seasonal variability of main elements of the ice regime (ice cover area, ice edge position, and ice period duration). Revealed are the common features and differences in the ice conditions in the water areas under study. It has been found that there is a significant feedback between the specific ice coverage in different areas of the sea. The climatic variations of the total ice coverage of the Barents Sea for the period of 1960?C2010 are analyzed using the electronic database on the Barents Sea ice coverage. It can be supposed that the current warm phase of climatic variations in the Barents Sea is coming to the end.     

Sea ice in the Barents Sea: seasonal to interannual variability and climate feedbacks in a global coupled model

Sea ice variability in the Barents Sea and its impact on climate are analyzed using a 465-year control integration of a global coupled atmosphere–ocean–sea ice model. Sensitivity simulations are performed to investigate the response to an isolated sea ice anomaly in the Barents Sea. The interannual variability of sea ice volume in the Barents Sea is mainly determined by variations in sea ice import into Barents Sea from the Central Arctic. This import is primarily driven by the local wind field. Horizontal oceanic heat transport into the Barents Sea is of minor importance for interannual sea ice variations but is important on longer time scales. Events with strong positive sea ice anomalies in the Barents Sea are due to accumulation of sea ice by enhanced sea ice imports and related NAO-like pressure conditions in the years before the event. Sea ice volume and concentration stay above normal in the Barents Sea for about 2 years after an event. This strongly increases the albedo and reduces the ocean heat release to the atmosphere. Consequently, air temperature is much colder than usual in the Barents Sea and surrounding areas. Precipitation is decreased and sea level pressure in the Barents Sea is anomalously high. The large-scale atmospheric response is limited with the main impact being a reduced pressure over Scandinavia in the year after a large ice volume occurs in the Barents Sea. Furthermore, high sea ice volume in the Barents Sea leads to increased sea ice melting and hence reduced surface salinity. Generally, the climate response is smallest in summer and largest in winter and spring.     

Low-frequency variability of the arctic climate: the role of oceanic and atmospheric heat transport variations

Changes in meridional heat transports, carried either by the atmosphere (HTRA) or by the ocean (HTRO), have been proposed to explain the decadal to multidecadal climate variations in the Arctic. On the other hand, model simulations indicate that, at high northern latitudes, variations in HTRA and HTRO are strongly coupled and may even compensate each other. A multi-century control integration with the Max Planck Institute global atmosphere-ocean model is analyzed to investigate the relative role of the HTRO and HTRA variations in shaping the Arctic climate and the consequences of their possible compensation. In the simulation, ocean heat transport anomalies modulate sea ice cover and surface heat fluxes mainly in the Barents Sea/Kara Sea region and the atmosphere responds with a modified pressure field. In response to positive HTRO anomalies there are negative HTRA anomalies associated with an export of relatively warm air southward to Western Siberia and a reduced inflow of heat over Alaska and northern Canada. While the compensation mechanism is prominent in this model, its dominating role is not constant over long time scales. The presence or absence of the compensation is determined mainly by the atmospheric circulation in the Pacific sector of the Arctic where the two leading large-scale atmospheric circulation patterns determine the lateral fluxes with varying contributions. The degree of compensation also determines the heat available to modulate the large-scale Arctic climate. The combined effect of atmospheric and oceanic contributions has to be considered to explain decadal-scale warming or cooling trends.     

Simulation of the Atlantic meridional overturning circulation in an atmosphere-ocean global coupled model. Part II: weakening in a climate change experiment: a feedback mechanism

Most state-of-the art global coupled models simulate a weakening of the Atlantic meridional overturning circulation (MOC) in climate change scenarios but the mechanisms leading to this weakening are still being debated. The third version of the CNRM (Centre National de Recherches Météorologiques) global atmosphere-ocean-sea ice coupled model (CNRM-CM3) was used to conduct climate change experiments for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4). The analysis of the A1B scenario experiment shows that global warming leads to a slowdown of North Atlantic deep ocean convection and thermohaline circulation south of Iceland. This slowdown is triggered by a freshening of the Arctic Ocean and an increase in freshwater outflow through Fram Strait. Sea ice melting in the Barents Sea induces a local amplification of the surface warming, which enhances the cyclonic atmospheric circulation around Spitzberg. This anti-clockwise circulation forces an increase in Fram Strait outflow and a simultaneous increase in ocean transport of warm waters toward the Barents Sea, favouring further sea ice melting and surface warming in the Barents Sea. Additionally, the retreat of sea ice allows more deep water formation north of Iceland and the thermohaline circulation strengthens there. The transport of warm and saline waters toward the Barents Sea is further enhanced, which constitutes a second positive feedback.     

Hydrometeorological conditions in the Barents Sea during El Niño of 1997–1998

Interadapted fields of main hydrophysical characteristics in the vicinity of hydrological sections carried out in 1997–1998 in the Barents Sea are obtained on the basis of model computations. The complex analysis of these materials and atmospheric situation in the region during 1997–1998 enabled to estimate quantitatively the variations of significant hydrodynamic conditions: the decrease in the inflow of rather warm and salty North Atlantic waters and the compensation inflow of polar waters, the decrease in total heat content and the weakening of water dynamics in the system of the general cyclonic circulation, and the increase in the ice coverage of the Barents Sea in anomalously cold winter 1997/98. It is revealed with a high degree of the confidence probability that the significant deviations from the normal conditions occur in response to the global El Niño disturbance which took place in the same years with the maximum values of the Southern Oscillation Index in January–March 1998.     

Arctic climate change in 21st century CMIP5 simulations with EC-Earth

The Arctic climate change is analyzed in an ensemble of future projection simulations performed with the global coupled climate model EC-Earth2.3. EC-Earth simulates the twentieth century Arctic climate relatively well but the Arctic is about 2 K too cold and the sea ice thickness and extent are overestimated. In the twenty-first century, the results show a continuation and strengthening of the Arctic trends observed over the recent decades, which leads to a dramatically changed Arctic climate, especially in the high emission scenario RCP8.5. The annually averaged Arctic mean near-surface temperature increases by 12 K in RCP8.5, with largest warming in the Barents Sea region. The warming is most pronounced in winter and autumn and in the lower atmosphere. The Arctic winter temperature inversion is reduced in all scenarios and disappears in RCP8.5. The Arctic becomes ice free in September in all RCP8.5 simulations after a rapid reduction event without recovery around year 2060. Taking into account the overestimation of ice in the twentieth century, our model results indicate a likely ice-free Arctic in September around 2040. Sea ice reductions are most pronounced in the Barents Sea in all RCPs, which lead to the most dramatic changes in this region. Here, surface heat fluxes are strongly enhanced and the cloudiness is substantially decreased. The meridional heat flux into the Arctic is reduced in the atmosphere but increases in the ocean. This oceanic increase is dominated by an enhanced heat flux into the Barents Sea, which strongly contributes to the large sea ice reduction and surface-air warming in this region. Increased precipitation and river runoff lead to more freshwater input into the Arctic Ocean. However, most of the additional freshwater is stored in the Arctic Ocean while the total Arctic freshwater export only slightly increases.     

Possible implications of climatic variability on the presence of capelin (Mallotus villosus) off the Norwegian coast

The distribution of capelin in the southern Barents Sea shifts in the east-west direction in response to warming or cooling trends. The capelin arrives at the spawning grounds earlier and spawning takes place in deeper water in cold years as compared to warm years. Although the ultimate regulators of capelin distribution/abundance in the Barents Sea may involve complex interactions/responses between capelin and abiotic and biotic variables, water temperature was found to be a successful predictor and proximate regulator of capelin distribution/ abundance in that area.It has been maintained that capelin did not visit the Norwegian coastal waters during the turn of the 18th century and in 1830–1840. Yet, meteorological, oceanographic and ecological data hitherto presented provide cumulative evidence that capelin migrated to the Norwegian spawning grounds during both periods. Nevertheless, capelin arrived early in the year and remained and spawned further offshore in deeper waters. Since capelin in earlier fisheries were fished by means of land-fixed nets, the size of the catch depended on access by the capelin to the immediate coastal fishing areas. Thus, capelin were not accessible to Norwegian fishermen.     

Economic impacts on key Barents Sea fisheries arising from changes in the strength of the Atlantic thermohaline circulation

A bioeconomic model of key fisheries of the Barents Sea is run with scenarios generated by an earth system model of intermediate complexity to assess how the Barents Sea fisheries of cod (Gadus morhua) and capelin (Mallotus villosus) are affected by changes in the Atlantic thermohaline circulation (THC) arising from anthropogenic climate change. Changes in hydrographic conditions have an impact on recruitment success and survival rates, which constitute a lasting effect on the stocks. The economic development of the fisheries is determined for the 21st century, considering a purely stock size based and a coupled stock size-hydrography based harvesting strategy. Results show that a substantial weakening of the THC leads to impaired cod stock development, causing the associated fishery to become unprofitable in the long run. Simultaneous improvements in capelin stock development help the capelin fishery, but are insufficient to offset the losses incurred by the cod fishery. A comparison of harvest strategies reveals that in times of high variability in stock development, coupled stock size-hydrography based management leads to more stable economic results of these fisheries than the stock size based fishing strategy.     

Climate and oceanic fisheries: recent observations and projections and future needs

Several lines of evidence show that climatic variation and global warming can have a major effect on fisheries production and replenishment. To prevent overfishing and rebuild overfished stocks under changing and uncertain environmental conditions, new research partnerships between fisheries scientists and climate change experts are required. The International Workshop on Climate and Oceanic Fisheries held in Rarotonga, Cook Islands, 3–5 October 2011, brought representatives from these disciplines together to consider the effects of climate variability and change on oceanic fisheries, the tools and strategies required for identifying potential impacts on oceanic fisheries, and the priority adaptations for sustaining future harvests, especially in the Pacific Ocean. Recommendations made by the workshop included (1) development and implementation of sustainable management measures for fisheries; (2) long-term commitment to monitoring necessary to assess stock status and to conduct integrated ecosystem assessments; (3) process oriented research to evaluate the potential of marine species for adaptation to a changing ocean environment; (4) provision of improved national meteorological and hydrological services to fisheries agencies, enterprises and communities; (5) continuing communication of potential impacts and adaptation strategies to stakeholders to reduce the threats to oceanic fisheries and capitalise on opportunities; and (6) continued collaborative efforts between meteorological, oceanographic, biological and fisheries researchers and management agencies to better monitor and understand the impacts of short-term variability and longer-term change on oceanic fisheries.     

冬春季节北极海冰的年际和年代际变化

利用1953～1990年海冰密集度资料,研究了冬、春季节北极海冰的时空变化特征.结果表明:冬,春季节海冰变率大的海区主要有巴伦支海、格陵兰海、巴芬湾、戴维斯海峡以及白令海;在巴芬湾、戴维斯海峡和白令海海区,冬季海冰变率比春季的大;冬、春季节喀拉海、巴伦支海海冰面积均与春季白令海海冰面积呈反向变化关系,与巴芬湾、戴维斯海峡海冰面积也存在相反的变化趋势.分析还表明:北极海冰面积还表现出年代际时间尺度变化,尤其在冬季.春季格陵兰海海冰明显存在12年变化周期,而在冬、春季节,喀拉海、巴伦支海海冰存在l0年变化周期.     

An Integrated Assessment of changes in the thermohaline circulation

This paper discusses the risks of a shutdown of the thermohaline circulation (THC) for the climate system, for ecosystems in and around the North Atlantic as well as for fisheries and agriculture by way of an Integrated Assessment. The climate model simulations are based on greenhouse gas scenarios for the 21st century and beyond. A shutdown of the THC, complete by 2150, is triggered if increased freshwater input from inland ice melt or enhanced runoff is assumed. The shutdown retards the greenhouse gas-induced atmospheric warming trend in the Northern Hemisphere, but does not lead to a persistent net cooling. Due to the simulated THC shutdown the sea level at the North Atlantic shores rises by up to 80 cm by 2150, in addition to the global sea level rise. This could potentially be a serious impact that requires expensive coastal protection measures. A reduction of marine net primary productivity is associated with the impacts of warming rather than a THC shutdown. Regional shifts in the currents in the Nordic Seas could strongly deteriorate survival chances for cod larvae and juveniles. This could lead to cod fisheries becoming unprofitable by the end of the 21st century. While regional socioeconomic impacts might be large, damages would be probably small in relation to the respective gross national products. Terrestrial ecosystem productivity is affected much more by the fertilization from the increasing CO₂ concentration than by a THC shutdown. In addition, the level of warming in the 22nd to 24th century favours crop production in northern Europe a lot, no matter whether the THC shuts down or not. CO₂ emissions corridors aimed at limiting the risk of a THC breakdown to 10% or less are narrow, requiring departure from business-as-usual in the next few decades. The uncertainty about THC risks is still high. This is seen in model analyses as well as in the experts’ views that were elicited. The overview of results presented here is the outcome of the Integrated Assessment project INTEGRATION.     

全球变暖背景下北极海冰与东亚冬季风关系的变化及其机制

为了进一步了解全球变暖背景下北极海冰与东亚冬季风的关系及其变化,本文选用东亚冬季风北模态及南模态作为东亚冬季风指数,利用滑动相关分析、回归分析及合成分析研究了全球变暖背景下1953—2021年北极海冰密集度与东亚冬季风关系的变化特征及其机制。结果表明:11月巴伦支海海冰密集度与东亚冬季风北模态之间的关系发生了显著变化,从1962—1977年显著正相关转为1983—1999年显著负相关,2000年以后两者无显著关系。1962—1977年11月巴伦支海海冰偏多对应东亚冬季风偏强,这是大气环流影响海冰的结果,11月的大气环流异常特征维持到了冬季,使得欧亚大陆上空大气呈现出北极涛动(Arctic Oscillation,AO)负位相,在增强东亚冬季风的同时将中高纬大陆干冷空气输送至巴伦支海,在表面风应力的作用下巴伦支海海冰增多。1983—1999年则由前一时期的大气环流影响海冰变为海冰影响大气环流,11月巴伦支海海冰显著减少在冬季激发出了北极涛动负位相,加强东亚大槽及东亚高空西风急流,从而使得东亚冬季风偏强。2000年以后北极海冰与东亚冬季风北模态的关系明显减弱,此时东亚冬季风与北极涛动的负相关关系更为显著。     

我国近海和邻近海的海洋环境对最近全球气候变化的响应

鉴于全球气候变暖对海洋环境和海洋生态及对经济和社会可持续发展影响的严重性,作者首先利用ERA-40再分析的风场资料以及HadISST 和SODA等海洋高分辨率再分析资料,分析了近50年来全球气候变化对中国近海(包括渤海、黄海、东海和南海)和邻近海(主要是热带和副热带西太平洋)海面附近的风力、海表纬向和经向风应力和海表温度的影响.分析结果表明: 由于受全球气候变暖的影响,1976年之后中国近海和邻近海上空的冬、夏季风变弱,从而引起中国近海冬、夏季海表风应力减弱(尤其是经向风应力),而海表水温明显上升; 并且,冬、夏季海表风应力的减弱和海水温度的上升在中国东海反映尤其明显,这些为中国近海赤潮的频繁发生提供了有利的海洋环境.此外,从中国近海上空环流散度分布的变化可见,中国近海上空从1976年之后大气环流辐散增强,这不利于中国近海上升流的形成,从而会对沿岸水域营养盐的输送产生影响.     

北极海冰年际变化对东亚中纬度夏季陆面热力异常的指示作用及其可能原因

本文分析了夏季东亚中纬度近地面温度和春、夏北极海冰时空变化特征,探讨了格陵兰海、巴伦支海海冰异常变化与夏季东亚中纬度陆面热力异常在年际上的可能联系。结果表明:(1)1950—2014年,东亚中纬度夏季近地面温度明显增暖,并伴有明显的年际变化,年际变率最大值的区域主要位于40°N以北至贝加尔湖地区;春、夏格陵兰海和巴伦支海的海冰也呈现明显的减少趋势,同时表现出较强的年际变化特征。(2)春、夏格陵兰海、巴伦支海海冰异常对东亚中纬度夏季陆面热力异常具有一定的指示作用:春、夏格陵兰海、巴伦支海海冰异常偏多,通常对应夏季东亚中纬度近地面的东亚中纬度夏季增暖现象;反之亦然。(3)春、季格陵兰海、巴伦支海北极海冰指数(Arctic Sea Ice Index,ASII)高值年(海冰异常偏多年份),贝加尔湖及西南的蒙古高原地区通常为大范围的异常高压控制,有利于近地面温度升高;同时由于乌拉尔山阻塞高压减弱,极地南下的冷空气减弱,有利于东亚中纬度区域的温度升高。而ASII低值年的情形则相反,贝加尔湖以南地区受异常低压控制,乌拉尔山阻塞高压增强,冷空气易向南侵袭,不利于东亚中纬度近地面升温。     

Can marine fisheries and aquaculture meet fish demand from a growing human population in a changing climate?

Expansion in the world's human population and economic development will increase future demand for fish products. As global fisheries yield is constrained by ecosystems productivity and management effectiveness, per capita fish consumption can only be maintained or increased if aquaculture makes an increasing contribution to the volume and stability of global fish supplies. Here, we use predictions of changes in global and regional climate (according to IPCC emissions scenario A1B), marine ecosystem and fisheries production estimates from high resolution regional models, human population size estimates from United Nations prospects, fishmeal and oil price estimations, and projections of the technological development in aquaculture feed technology, to investigate the feasibility of sustaining current and increased per capita fish consumption rates in 2050. We conclude that meeting current and larger consumption rates is feasible, despite a growing population and the impacts of climate change on potential fisheries production, but only if fish resources are managed sustainably and the animal feeds industry reduces its reliance on wild fish. Ineffective fisheries management and rising fishmeal prices driven by greater demand could, however, compromise future aquaculture production and the availability of fish products.     

Present-day and future precipitation in the Baltic Sea region as simulated in a suite of regional climate models

Here we investigate simulated changes in the precipitation climate over the Baltic Sea and surrounding land areas for the period 2071–2100 as compared to 1961–1990. We analyze precipitation in 10 regional climate models taking part in the European PRUDENCE project. Forced by the same global driving climate model, the mean of the regional climate model simulations captures the observed climatological precipitation over the Baltic Sea runoff land area to within 15% in each month, while single regional models have errors up to 25%. In the future climate, the precipitation is projected to increase in the Baltic Sea area, especially during winter. During summer increased precipitation in the north is contrasted with a decrease in the south of this region. Over the Baltic Sea itself the future change in the seasonal cycle of precipitation is markedly different in the regional climate model simulations. We show that the sea surface temperatures have a profound impact on the simulated hydrological cycle over the Baltic Sea. The driving global climate model used in the common experiment projects a very strong regional increase in summertime sea surface temperature, leading to a significant increase in precipitation. In addition to the common experiment some regional models have been forced by either a different set of Baltic Sea surface temperatures, lateral boundary conditions from another global climate model, a different emission scenario, or different initial conditions. We make use of the large number of experiments in the PRUDENCE project, providing an ensemble consisting of more than 25 realizations of climate change, to illustrate sources of uncertainties in climate change projections.