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Climate Regime Shifts (climate + regime_shift)
Selected AbstractsEffects of decadal climate change on zooplankton over the last 50 years in the western subarctic North PacificGLOBAL CHANGE BIOLOGY, Issue 5 2006SANAE CHIBA Abstract Decadal- to multi-decadal variations have been reported in many regional ecosystems in the North Pacific, resulting in an increasing demand to elucidate the link between long-term climatic forcing and marine ecosystems. We detected phenological and quantitative changes in the copepod community in response to the decadal climatic variation in the western subarctic North Pacific by analyzing the extensive zooplankton collection taken since the 1950s, the Odate Collection. Copepod species were classified into five seasonal groups depending on the timing of the annual peak in abundance. The abundance of the spring community gradually increased for the period 1960,2002. The spring,summer community also showed an increasing trend in May, but a decadal oscillation pattern of quasi-30-year cycles in July. Phenological changes coincided with the climate regime shift in the mid-1970s, indicated by the Pacific decadal oscillation index (PDO). After the regime shift, the timing of the peak abundance was delayed one month, from March,April to April,May, in the spring community, whereas it peaked earlier, from June,July to May,June, in the spring,summer community, resulting in an overlap of the high productivity period for the two communities in May. Wintertime cooling, followed by rapid summertime warming, was considered to be responsible for delayed initiation and early termination of the productive season after the mid-1970s. Another phenological shift, quite different from the previous decade, was observed in the mid-1990s, when warm winters followed by cool summers lengthened the productive season. The results suggest that climatic forcing with different decadal cycles may operate independently during winter,spring and spring,summer to create seasonal and interannual variations in hydrographic conditions; thus, combinations of these seasonal processes may determine the annual biological productivity. [source] Oscillating trophic control induces community reorganization in a marine ecosystemECOLOGY LETTERS, Issue 12 2007Michael A. Litzow Abstract Understanding how climate regulates trophic control may help to elucidate the causes of transitions between alternate ecosystem states following climate regime shifts. We used a 34-year time series of the abundance of Pacific cod (Gadus macrocephalus) and five prey species to show that the nature of trophic control in a North Pacific ecosystem depends on climate state. Rapid warming in the 1970s caused an oscillation between bottom,up and top,down control. This shift to top,down control apparently contributed to the transition from an initial, prey-rich ecosystem state to the final, prey-poor state. However, top,down control could not be detected in the final state without reference to the initial state and transition period. Complete understanding of trophic control in ecosystems capable of transitions between alternate states may therefore require observations spanning more than one state. [source] A framework for incorporating climate regime shifts into the management of marine resourcesFISHERIES MANAGEMENT & ECOLOGY, Issue 2 2006J. R. KING Abstract, It is possible to use an ecosystem-based management approach to incorporate knowledge of climate regime impacts on ecosystem productivity to manage fishery resources. To do so, it requires the development of a coherent framework that can be built using existing stock assessment and management activities: ecosystem assessment, risk analyses, adaptive management and reference points. This paper builds such a framework and uses two population simulations to illustrate the benefits and tradeoffs of variable regime-specific harvest rates. The framework does not require prediction of regime shifts, but assumes that detection can occur soon after one has happened. As such, decisions do not need to be coincident to regime shifts, but can be delayed by an appropriate period of time that is linked to a species' life history, i.e. age of maturity or recruitment. Fisheries scientists should provide harvest recommendations that reflect a range of levels of risk to the stock under different assumptions of productivity. Coupling ecosystem assessment with ecosystem-based management would allow managers to select appropriate regime-specific harvest rates. [source] Decadal-scale variability in the Kuroshio marine ecosystem in winterFISHERIES OCEANOGRAPHY, Issue 4-5 2003Kaoru Nakata Abstract Interannual variation of winter copepod biomass during the last three decades of the twentieth century was examined in the Kuroshio, off central Japan in relation to climate regime shifts. The biomass levels of large copepods in the period before 1977 and in 1999 and 2000 were higher than those in the period between 1977 and 1998. The biomass of large copepods was positively related with the Southern Oscillation Index (SOI), in winter in the Northern Hemisphere, which also showed steplike shifts in 1976/77 and 1998/99. The biomass of large copepods was largely influenced by abundance of Calanus sinicus that has high rates of production compared with small copepods under food satiated conditions. Accordingly, the climatic regime shift accompanied by the climatic change in the tropical region seems to regulate interannual variation of winter biomass of large copepods in the Kuroshio through effects on food supply. There is less decadal variablity in the small copepod (SC) biomass than large copepod (LC) biomass, but more variablity in SC than in LC at periods 2,4 years. In contrast to the large copepods, the biomass of small copepods was not related to global climate indices but with the local climate factors such as SST in the Kuroshio and variability in the Kuroshio flow path. Causes for the differences in the biomass trends between large and small copepods are discussed. [source] Projecting the risk of future climate shiftsINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 7 2006David B. Enfield Abstract Recent research has shown that decadal-to-multidecadal (D2M) climate variability is associated with environmental changes that have important consequences for human activities, such as public health, water availability, frequency of hurricanes, and so forth. As scientists, how do we convert these relationships into decision support products useful to water managers, insurance actuaries, and others, whose principal interest lies in knowing when future climate regime shifts will likely occur that affect long-horizon decisions? Unfortunately, numerical models are far from being able to make deterministic predictions for future D2M climate shifts. However, the recent development of paleoclimate reconstructions of the Atlantic Multidecadal Oscillation (AMO) (Gray et al., 2004) and Pacific Decadal Oscillation (PDO); (MacDonald and Case, 2005) give us a viable alternative: to estimate probability distribution functions from long climate index series that allow us to calculate the probability of future D2M regime shifts. In this paper, we show how probabilistic projections can be developed for a specific climate mode,the AMO as represented by the Gray et al. (2004) tree-ring reconstruction. The methods are robust and can be applied to any D2M climate mode for which a sufficiently long index series exists, as well as to the growing body of paleo-proxy reconstructions that have become available. The target index need not be a paleo-proxy calibrated against a climate index; it may profitably be calibrated against a specific resource of interest, such as stream flow or lake levels. Copyright © 2006 Royal Meteorological Society [source] | |||||||||||||