Strongly positive temperature anomalies developed in the NE Pacific Ocean during the boreal winter of 2013–2014. Based on a mixed layer temperature budget, these anomalies were caused by lower than ...normal rates of the loss of heat from the ocean to the atmosphere and of relatively weak cold advection in the upper ocean. Both of these mechanisms can be attributed to an unusually strong and persistent weather pattern featuring much higher than normal sea level pressure over the waters of interest. This anomaly was the greatest observed in this region since at least the 1980s. The region of warm sea surface temperature anomalies subsequently expanded and reached coastal waters in spring and summer 2014. Impacts on fisheries and regional weather are discussed. It is found that sea surface temperature anomalies in this region affect air temperatures downwind in Washington state.
Key Points
Anomalous atmospheric forcing in the NE Pacific in winter 2013–2014
Weak seasonal cooling due to reduced heat fluxes and anomalous advection
SST anomalies have impacts on the ecosystem and air temperatures
Climate change is likely to change the relationships between commonly used climate indices and underlying patterns of climate variability, but this complexity is rarely considered in studies using ...climate indices. Here, we show that the physical and ecological conditions mapping onto the Pacific Decadal Oscillation (PDO) index and North Pacific Gyre Oscillation (NPGO) index have changed over multidecadal timescales. These changes apparently began around a 1988/1989 North Pacific climate shift that was marked by abrupt northeast Pacific warming, declining temporal variance in the Aleutian Low (a leading atmospheric driver of the PDO), and increasing correlation between the PDO and NPGO patterns. Sea level pressure and surface temperature patterns associated with each climate index changed after 1988/1989, indicating that identical index values reflect different states of basinscale climate over time. The PDO and NPGO also show timedependent skill as indices of regional northeast Pacific ecosystem variability. Since the late 1980s, both indices have become less relevant to physical–ecological variability in regional ecosystems from the Bering Sea to the southern California Current. Users of these climate indices should be aware of nonstationary relationships with underlying climate variability within the historical record, and the potential for further nonstationarity with ongoing climate change.
Climate change has exacerbated the occurrence of large‐scale sea surface temperature anomalies, or marine heatwaves (MHWs)—extreme phenomena often associated with mass mortality events of marine ...organisms. Using a combination of citizen science and federal data sets, we investigated the causal mechanisms of the 2014/2015 die‐off of Cassin's Auklets (Ptychoramphus aleuticus), a small zooplanktivorous seabird, during the NE Pacific MHW of 2013–2015. Carcass deposition followed an effective reduction in the energy content of mesozooplankton, coincident with the loss of cold‐water foraging habitat caused by the intrusion of the NE Pacific MHW into the nearshore environment. Models examining interannual variability in effort‐controlled carcass abundance (2001–2014) identified the biomass of lipid‐poor zooplankton as the dominant predictor of increased carcass abundance. In 2014, Cassin's Auklets dispersing from colonies in British Columbia likely congregated into a nearshore band of cooler upwelled water and ultimately died from starvation following the shift in zooplankton composition associated with onshore transport of the NE Pacific MHW. For Cassin's Auklets, already in decline due to ocean warming, large‐scale and persistent MHWs might represent a global population precipice.
Plain Language Summary
During the winter of 2014/2015, thousands of Cassin's Auklets, a small seabird that breeds in the NE Pacific, were found dead on beaches from California to British Columbia, Canada. We show that wide‐scale starvation was due to a change in food quality associated with warmer ocean temperatures preceding and during the die‐off. This research highlights that more frequent and intense ocean warming events may have complex impacts on food webs with population consequences for marine predators, particularly seabirds such as Cassin's Auklets.
Key Points
During the winter of 2014/2015, over 9,000 (>100 x normal) dead Cassin's Auklets were observed on beaches from California to British Columbia
The die‐off was ultimately caused by a reduction in zooplankton prey energy content as a result of the NE Pacific marine heatwave (MHW)
The NE Pacific MHW likely inflated event magnitude by compressing cold‐water habitat, and by proxy live birds, closer to shore than usual
ABSTRACT We present photometry and derived redshifts from up to eleven bandpasses for 9927 galaxies in the Hubble Ultra Deep field (UDF), covering an observed wavelength range from the ...near-ultraviolet (NUV) to the near-infrared (NIR) with Hubble Space Telescope observations. Our Wide Field Camera 3 (WFC3)/UV F225W, F275W, and F336W image mosaics from the ultra-violet UDF (UVUDF) imaging campaign are newly calibrated to correct for charge transfer inefficiency, and use new dark calibrations to minimize background gradients and pattern noise. Our NIR WFC3/IR image mosaics combine the imaging from the UDF09 and UDF12 campaigns with CANDELS data to provide NIR coverage for the entire UDF field of view. We use aperture-matched point-spread function corrected photometry to measure photometric redshifts in the UDF, sampling both the Lyman break and Balmer break of galaxies at - , and one of the breaks over the rest of the redshift range. Our comparison of these results with a compilation of robust spectroscopic redshifts shows an improvement in the galaxy photometric redshifts by a factor of two in scatter and a factor three in outlier fraction (OLF) over previous UDF catalogs. The inclusion of the new NUV data is responsible for a factor of two decrease in the OLF compared to redshifts determined from only the optical and NIR data, and improves the scatter at and at . The panchromatic coverage of the UDF from the NUV through the NIR yields robust photometric redshifts of the UDF, with the lowest OLF available.
Changes in upper ocean stratification during the second half of the 21st century, relative to the second half of the 20th century, are examined in ten of the CMIP3 climate models according to the ...SRES‐A2 scenario. The upper ocean stratification, defined here as the density difference between 200 m and the surface, is larger everywhere during the second half of the 21st century, indicative of an increasing degree of decoupling between the surface and the deeper oceans, with important consequences for many biogeochemical processes. The areas characterized by the largest stratification changes include the Arctic, the tropics, the North Atlantic, and the northeast Pacific. The increase in stratification is primarily due to the increase in surface temperature, whose influence upon density is largest in the tropical regions, and decreases with increasing latitude. The influence of salinity upon the stratification changes, while not as spatially extensive as that of temperature, is very large in the Arctic, North Atlantic and Northeast Pacific. Salinity also significantly contributes to the density decrease near the surface in the western tropical Pacific, but counteracts the negative influence of temperature upon density in the tropical Atlantic.
Key Points
Changes in SST and SSS lead to changes in stratification
Increasing temperatures reduce surface density
Salinity can have a large influence on density in specific regions
The ability of management strategies to achieve the fishery management goals are impacted by environmental variation and, therefore, also by global climate change. Management strategies can be ...modified to use environmental data using the "dynamic B sub(0)" concept, and changing the set of years used to define biomass reference points. Two approaches have been developed to apply management strategy evaluation to evaluate the impact of environmental variation on the performance of management strategies. The "mechanistic approach" estimates the relationship between the environment and elements of the population dynamics of the fished species and makes predictions for population trends using the outputs from global climate models. In contrast, the "empirical approach" examines possible broad scenarios without explicitly identifying mechanisms. Many reviewed studies have found that modifying management strategies to include environmental factors does not improve the ability to achieve management goals much, if at all, and only if the manner in which these factors drive the system is well known. As such, until the skill of stock projection models improves, it seems more appropriate to consider the implications of plausible broad forecasts related to how biological parameters may change in the future as a way to assess the robustness of management strategies, rather than attempting specific predictions per se.
The two leading modes of North Pacific sea surface temperature (SST) and sea level pressure (SLP), as well as their connections to tropical variability, are explored in the 24 coupled climate models ...used in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) to evaluate North Pacific decadal variability (NPDV) in the past twentieth century; climate of the twentieth century (20C3M) scenario and future twenty-first century; Special Report on Emissions Scenarios (SRES) A1B scenario climate. Results indicate that the two dominant modes of North Pacific oceanic variability, the Pacific decadal oscillation (PDO) and the North Pacific Gyre Oscillation (NPGO), do not exhibit significant changes in their spatial and temporal characteristics under greenhouse warming. However, the ability of the models to capture the dynamics associated with the leading North Pacific oceanic modes, including their link to the corresponding atmospheric forcing patterns and to tropical variability, is questionable.
The temporal and spatial statistics of the North Pacific Ocean modes exhibit significant discrepancies from observations in their twentieth-century climate, most visibly for the second mode, which has significantly more low-frequency power and higher variance than in observations. The dynamical coupling between the North Pacific Ocean and atmosphere modes evident in the observations is very strong in the models for the first atmosphere–ocean coupled mode, which represents covariability of the PDO pattern with the Aleutian low (AL). However, the link for the second atmosphere–ocean coupled mode, describing covariability of an NPGO-like SST pattern with the North Pacific Oscillation (NPO), is not as clearly reproduced, with some models showing no relationship between the two.
Exploring the tropical Pacific–North Pacific teleconnections reveals more issues with the models. In contrast with observations, the atmospheric teleconnection excited by the El Niño–Southern Oscillation in the models does not project strongly on the AL–PDO coupled mode because of the displacement of the center of action of the AL in most models. Moreover, most models fail to show the observational connection between El Niño Modoki–central Pacific warming and NPO variability in the North Pacific. In fact, the atmospheric teleconnections associated with El Niño Modoki in some models have a significant projection on, and excite the AL–PDO coupled mode instead. Because of the known links between tropical Pacific variability and NPDV, these analyses demonstrate that focus on the North Pacific variability of climate models in isolation from tropical dynamics is likely to lead to an incomplete view, and inadequate prediction, of NPDV.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We present the Smoothed Hessian Major Axis Filament Finder (shmaff), an algorithm that uses the eigenvectors of the Hessian matrix of the smoothed galaxy distribution to identify individual ...filamentary structures. Filaments are traced along the Hessian eigenvector corresponding to the largest eigenvalue and are stopped when the axis orientation changes more rapidly than a preset threshold. In both N-body simulations and the Sloan Digital Sky Survey (SDSS) main galaxy redshift survey data, the resulting filament length distributions are approximately exponential. In the SDSS galaxy distribution, using smoothing lengths of 10 and 15 h−1 Mpc, we find filament lengths per unit volume of 1.9 × 10−3 and 7.6 × 10−4 h2 Mpc−2, respectively. The filament width distributions, which are much more sensitive to non-linear growth, are also consistent between the real and mock galaxy distributions using a standard cosmology. In SDSS, we find mean filament widths of 5.5 and 8.4 h−1 Mpc on 10 and 15 h−1 Mpc smoothing scales, with standard deviations of 1.1 and 1.4 h−1 Mpc, respectively. Finally, the spatial distribution of filamentary structure in simulations is very similar between z= 3 and z= 0 on smoothing scales as large as 15 h−1 Mpc, suggesting that the outline of filamentary structure is already in place at high redshift.
Mueter, F. J., Bond, N. A., Ianelli, J. N., and Hollowed, A. B. 2011. Expected declines in recruitment of walleye pollock (Theragra chalcogramma) in the eastern Bering Sea under future climate ...change. - ICES Journal of Marine Science, 68: 1284-1296.
A statistical model is developed to link recruitment of eastern Bering Sea walleye pollock (Theragra chalcogramma) to variability in late summer sea surface temperatures and to the biomass of major predators. The model is based on recent advances in the understanding of pollock recruitment, which suggest that warm spring conditions enhance the survival of early larvae, but high temperatures in late summer and autumn are associated with poor feeding conditions for young-of-year pollock and reduced recruitment in the following year. A statistical downscaling approach is used to generate an ensemble of late summer temperature forecasts through 2050, based on a range of IPCC climate projections. These forecasts are used to simulate future recruitment within an age-structured stock projection model that accounts for density-dependent effects (stock-recruitment relationship), the estimated effects of temperature and predation, and associated uncertainties. On average, recruitment in 2040-2050 should expectedly decline by 32-58% relative to a random recruitment scenario, depending on assumptions about the temperature relationship, the magnitude of density-dependence, and future changes in predator biomass. The approach illustrated here can be used to evaluate the performance of different management strategies and provide long-term strategic advice to managers confronted with a rapidly changing climate.
Ocean–atmosphere interaction over the Northern Hemisphere western boundary current (WBC) regions (i.e., the Gulf Stream, Kuroshio, Oyashio, and their extensions) is reviewed with an emphasis on their ...role in basin-scale climate variability. SST anomalies exhibit considerable variance on interannual to decadal time scales in these regions. Low-frequency SST variability is primarily driven by basin-scale wind stress curl variability via the oceanic Rossby wave adjustment of the gyre-scale circulation that modulates the latitude and strength of the WBC-related oceanic fronts. Rectification of the variability by mesoscale eddies, reemergence of the anomalies from the preceding winter, and tropical remote forcing also play important roles in driving and maintaining the low-frequency variability in these regions. In the Gulf Stream region, interaction with the deep western boundary current also likely influences the low-frequency variability. Surface heat fluxes damp the low-frequency SST anomalies over the WBC regions; thus, heat fluxes originate with heat anomalies in the ocean and have the potential to drive the overlying atmospheric circulation. While recent observational studies demonstrate a local atmospheric boundary layer response to WBC changes, the latter’s influence on the large-scale atmospheric circulation is still unclear. Nevertheless, heat and moisture fluxes from the WBCs into the atmosphere influence the mean state of the atmospheric circulation, including anchoring the latitude of the storm tracks to the WBCs. Furthermore, many climate models suggest that the large-scale atmospheric response to SST anomalies driven by ocean dynamics in WBCregions can be important in generating decadal climate variability. As a step toward bridging climate model results and observations, the degree of realism of the WBC in current climate model simulations is assessed. Finally, outstanding issues concerning ocean–atmosphere interaction in WBC regions and its impact on climate variability are discussed.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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