ALBERT

Description: In this study, the authors discuss two different parameterizations for the effect of mixed layer eddies, one based on ageostrophic linear stability analysis (ALS) and the other one based on a scaling of the potential energy release by eddies (PER). Both parameterizations contradict each other in two aspects. First, they predict different functional relationships between the magnitude of the eddy fluxes and the Richardson number (Ri) related to the background state. Second, they also predict different vertical structure functions for the horizontal eddy fluxes. Numerical simulations for two different configurations and for a large range of different background conditions are used to evaluate the parameterizations. It turns out that PER is better suited to capture the Ri dependency of the magnitude of the eddy fluxes. On the other hand, the vertical structure of the meridional eddy fluxes predicted by ALS is more accurate than that of PER, while the vertical structure of the vertical eddy fluxes is well predicted by both parameterizations. Therefore, this study suggests the use of the magnitude of PER and the vertical structure functions of ALS for an improved parameterization of mixed layer eddy fluxes.

Description: The dynamics of accretionary convergent margins are severely influenced by intense deformation and fluid expulsion. To quantify the fluid pressure and fluid flow velocities in the Hellenic subduction system, we set up 2-D hydrogeological numerical models following two seismic reflection lines across the Mediterranean Ridge. These profiles bracket the along-strike variation in wedge geometry: moderate compression and a 〉4 km thick underthrust sequence in the west versus enhanced compression and 〈1 km of downgoing sediment in the center. Input parameters were obtained from preexisting geophysical data, drill cores, and new geotechnical laboratory experiments. A permeability-porosity relationship was determined by a sensitivity analysis, indicating that porosity and intrinsic permeability are small. This hampers the expulsion of fluids and leads to the build up of fluid overpressure in the deeper portion of the wedge and in the underthrust sediment. The loci of maximum fluid pressure are mainly controlled by the compactional fluid source, which generally decreases toward the backstop. However, pore pressure is still high at the decollement level at distances 〈100 km from the deformation front, either by the incorporation of low permeability evaporites or additional compaction of the wedge sediments in the two profiles. In the west, however, formation of a wide accretionary complex is facilitated by high pore pressure zones. When compared to other large accretionary complexes such as Nankai or Barbados, our results not only show broad similarities but also that near-lithostatic pore pressures may be easier to maintain in the Hellenic Arc because of accentuated collision, some underthrust evaporates, and a thicker underthrust sequence.

Description: Northern Hemisphere stratospheric variability is investigated with respect to chaotic behavior using time series from three different variables extracted from four different reanalysis products and two numerical model runs with different forcing. The time series show red spectra at all frequencies and the probability distribution functions show persistent deviations from a Gaussian distribution. An exception is given by the numerical model forced with perpetual winter conditions—a case that shows more variability and follows a Gaussian distribution, suggesting that the deviation from Gaussianity found in the observations is due to the transition between summer and winter variability. To search for the presence of a chaotic attractor the correlation dimension and entropy, the Lyapunov spectrum, and the associated Kaplan–Yorke dimension are estimated. A finite value of the dimensions can be computed for each variable and data product, with the correlation dimension ranging between 3.0 and 4.0 and the Kaplan–Yorke dimension between 3.3 and 5.5. The correlation entropy varies between 0.6 and 1.1. The model runs show similar values for the correlation and Lyapunov dimensions for both the seasonally forced run and the perpetual-winter run, suggesting that the structure of a possible chaotic attractor is not determined by the seasonality in the forcing, but must be given by other mechanisms.

Description: Southern Hemisphere (SH) stratospheric variability is investigated with respect to chaotic behavior using time series from three different variables extracted from four different reanalysis products. The results are compared with the same analysis applied to the Northern Hemisphere (NH). The probability density functions (PDFs) for the SH show persistent deviations from a Gaussian distribution. The variability is given by white spectra for low frequencies, a slope of −1 for intermediate frequencies, and −3 slopes for high frequencies. Considering the time series for winter and summer separately, PDFs show a Gaussian distribution and the variability spectra change their slopes, indicating the role of the transition between winter and summer variability in shaping the time series. The correlation (D2) and the Kaplan–Yorke (DKY) dimensions are estimated. A finite value of the dimensions can be computed for each variable and data product, except for the NCEP zonal-mean zonal wind and temperature data, which violate the requirement D2 ≤ DKY, possibly owing to the presence of spurious trends and inconsistencies in the data. The value of D2 ranges between 2.6 and 3.9, while DKY ranges between 3.0 and 4.5. The results show that both D2 and DKY display large variability in their values both for different datasets and for different variables within the same dataset. The variability of the values of D2 and DKY thus leaves open the question about the existence of a low-dimensional attractor or if the finite dimensions of the system are the result of the projection of a larger attractor in a low-dimensional embedding space.

Description: The sensitivities of the Brewer–Dobson circulation (BDC) to different distributions of tropical SST heating are investigated in an idealized aquaplanet model. It is found that an increase in tropical SSTs generally leads to an acceleration of tropical upwelling and an associated reduction in the age of air (AOA) in the polar stratosphere and that the AOA near the subtropical tropopause is correlated with local isentropic mixing of tropospheric air with stratospheric air. The zonal distribution of SST perturbations has a major impact on the vertical and meridional structure of the BDC as compared with other SST characteristics. Zonally localized SST heatings tend to generate a shallow acceleration of the stratospheric residual circulation, enhanced isentropic mixing associated with a weakened stratospheric jet, and a reduction in AOA mostly within the polar vortex. In contrast, SST heatings with a zonally symmetric structure tend to produce a deep strengthening of the stratospheric residual circulation, suppressed isentropic mixing associated with a stronger stratospheric jet, and a decrease of AOA in the entire stratosphere. The shallow versus deep strengthening of the stratospheric residual circulation change has been linked to wave propagation and dissipation in the subtropical lower stratosphere rather than wave generation in the troposphere, and the former can be strongly affected by the vertical position of the subtropical jet. These results suggest that, while the longitudinally localized SST trends under climate change may contribute to the change in the shallow branch of the BDC, the upward shift of the subtropical jet associated with the zonal SST heating can impact the deep branch of the BDC.

Description: The authors test the hypothesis that recent observed trends in surface westerlies in the Southern Hemisphere are directly consequent on observed trends in the timing of stratospheric final warming events. The analysis begins by verifying that final warming events have an impact on tropospheric circulation in a simplified GCM driven by specified equilibrium temperature distributions. Seasonal variations are imposed in the stratosphere only. The model produces qualitatively realistic final warming events whose influence extends down to the surface, much like what has been reported in observational analyses. The authors then go on to study observed trends in surface westerlies composited with respect to the date of final warming events. If the considered hypothesis were correct, these trends would appear to be much weaker when composited with respect to the date of the final warming events. The authors find that this is not the case, and accordingly they conclude that the observed surface changes cannot be attributed simply to this shift toward later final warming events.

Description: Precipitation is highly variable in space and time; hence, rain gauge time series generally exhibit additional random small-scale variability compared to area averages. Therefore, differences between daily precipitation statistics simulated by climate models and gauge observations are generally not only caused by model biases, but also by the corresponding scale gap. Classical bias correction methods, in general, cannot bridge this gap; they do not account for small-scale random variability and may produce artifacts. Here, stochastic model output statistics is proposed as a bias correction framework to explicitly account for random small-scale variability. Daily precipitation simulated by a regional climate model (RCM) is employed to predict the probability distribution of local precipitation. The pairwise correspondence between predictor and predictand required for calibration is ensured by driving the RCM with perfect boundary conditions. Wet day probabilities are described by a logistic regression, and precipitation intensities are described by a mixture model consisting of a gamma distribution for moderate precipitation and a generalized Pareto distribution for extremes. The dependence of the model parameters on simulated precipitation is modeled by a vector generalized linear model. The proposed model effectively corrects systematic biases and correctly represents local-scale random variability for most gauges. Additionally, a simplified model is considered that disregards the separate tail model. This computationally efficient model proves to be a feasible alternative for precipitation up to moderately extreme intensities. The approach sets a new framework for bias correction that combines the advantages of weather generators and RCMs.

Description: No published information is available on the foraging ecology and choice of feeding habitat of New Zealand’s rarest breeding bird: the New Zealand Fairy Tern (NZFT) Sternula nereis davisae. To address this gap, we conducted an assessment of the largest remaining breeding population at Mangawhai Harbour, Northland, New Zealand, during the chick-rearing period of the 2010/2011 breeding season. We combined visual tracking of birds with prey surveys and stable isotope analyses, and we present the first quantitative assessment of NZFT foraging. We recorded 405 foraging dives that show NZFT foraging habitat includes the water edges, shallow channels, and pools on the tidal flats of mangrove-lined (Avicennia marina var. resinifera) parts of the estuary; tidal pools on mud- and sandflats in the mid-estuary and lower harbour; the shallow margins of the dredged main channel in the lower harbour; the oxbow lagoons on the sand spit; and coastal shallows. Our study identifies the mangrove-lined highly tidal and shallow mid-estuary and the lagoon on the sand spit as foraging hotspots for the Mangawhai breeding population of the NZFT. The prey survey employed a seine-net sampling method at identified NZFT foraging sites and yielded 4,367 prey-sized fish of 11 species, two of which had not previously been reported in Mangawhai Harbour, as well as numerous shrimps. The most abundant fish were gobies of the genus Favonigobius. Our stable isotope results highlight gobies as the most important prey for NZFT chick rearing, also indicating that flounder Rhombosolea sp. contribute to NZFT diet. We raise the possibility that shrimps may also constitute a substantial diet component for NZFT, potentially providing up to 21% of diet mass for adult birds. While our results provide a first basis to understanding the feeding ecology of NZFT during their breeding season in order to facilitate conservation planning, further research is required to address inter-annual variation and to identify key foraging grounds for this Critically Endangered bird at other breeding sites.

Description: There is an ongoing discussion in the community concerning the wave-averaged momentum equations in the hybrid vertically Lagrangian and horizontally Eulerian (VL) framework and, in particular, the form stress term (representing the residual effect of pressure perturbations) which is thought to restrict the handling of higher order waves in terms of a perturbation expansion. The present study shows that the traditional pressure-based form stress term can be transformed into a set of terms that do not contain any pressure quantities but do contain the time derivative of a wave-induced velocity. This wave-induced velocity is referred to as the pseudomomentum in the VL framework, as it is analogous to the generalized pseudomomentum in Andrews and McIntyre. This enables the second expression for the wave-averaged momentum equations in the VL framework (this time for the development of the total transport velocity minus the VL pseudomomentum) to be derived together with the vortex force. The velocity-based expression of the form stress term also contains the residual effect of the turbulent viscosity, which is useful for understanding the dissipation of wave energy leading to transfer of momentum from waves to circulation. It is found that the concept of the virtual wave stress of Longuet-Higgins is applicable to quite general situations: it does not matter whether there is wind forcing or not, the waves can have slow variations, and the viscosity coefficient can vary in the vertical. These results provide a basis for revisiting the surface boundary condition used in numerical circulation models.

Description: Mooring observations and model simulations point to an instability of the Labrador Current (LC) during winter, with enhanced eddy kinetic energy (EKE) at periods between 2 to 5 days, and much less EKE during other seasons. Linear stability analysis using vertical shear and stratification from the model reveals three dominant modes of instability in the LC: - a balanced interior mode with along-flow wavelengths of about 30–45 km, phase velocities of 0.3 m/s, maximal growth rates of 1 d−1 and surface intensified, but deep reaching amplitudes, - a balanced shallow mode with along-flow wavelengths of about 0.3–1.5 km, about three times larger phase speeds and growth rates, but amplitudes confined to the mixed layer (ML), - and an unbalanced symmetric mode with largest growth rates, vanishing phase speeds and along-flow structure, and very small cross-flow wavelengths, also confined to the ML. Both balanced modes are akin to baroclinic instability, but operate at moderate to small Richardson numbers Ri with much larger growth rates as for the quasi-geostrophic limit of Ri ≫ 1. The interior mode is found to be responsible for the instability of the LC during winter. Weak stratification and enhanced vertical shear due to local buoyancy loss and the advection of convective water masses from the interior result in small Ri within the LC, and to three times larger growth rates of the interior mode in March compared to summer and fall conditions. Both the shallow and the symmetric mode are not resolved by the model, but it is suggested that they might also play an important role for the instability in the LC and for lateral mixing.

Description: Sensible and latent heat fluxes were estimated from turbulence measurements gathered during several Atlantic transects of the R/V Polarstern. The inertial dissipation method was used to analyze the data. Resulting bulk transfer coefficients were then applied to the data from the ship’s meteorological system to get continuous time series of the heat fluxes. Combined to the measured downward solar and longwave radiation fluxes allows for an estimate of the total energy budget at the air-sea interface. Comparing these parameterized energy fluxes to ones based on the COARE 3.0 bulk flux algorithm show very strong agreement.

Description: The dynamical origin of the spectral and autocorrelation structure of annular variability in the troposphere is investigated by a deductive approach. Specifically, the structure of the power spectrum and autocorrelation function of the zonal-mean geopotential is analyzed for the case of a quasigeostrophic spherical atmosphere subject to a white noise mechanical forcing applied in a single Hough mode and concentrated at a particular level in the vertical, with vertically uniform Newtonian cooling and Rayleigh drag concentrated at a rigid lower boundary. Analytic expressions for the power spectrum are presented together with expressions for an approximate red noise (i.e., a Lorentzian-shaped) power spectrum. It is found that for an infinitely deep atmosphere the power spectrum can be well approximated by a red noise process for the first few Hough modes (associated with large Rossby heights), provided the distance from the forcing is not larger than about one Rossby height. When a frictional rigid lower boundary is included, however, the approximation is generally bad. The high-frequency part of the power spectrum exhibits near-exponential behavior and the autocorrelation function shows a transition from a rapid decay at short lags to a much slower decay at longer lags, if the thermal and mechanical damping time scales are sufficiently well separated. Since observed annular variability exhibits the same characteristics, the above results lead to the hypothesis that these characteristics may, to some extent, be intrinsic to the linear zonal-mean response problem—although the need for an additional contribution from eddy feedbacks is also implied by the results.

Description: A representation of an equatorial basin mode excited in a shallow water model for a single high order baroclinic vertical normal mode is used as a simple model for the equatorial deep jets. The model is linearized about both a state of rest and a barotropic mean flow corresponding to the observed Atlantic Equatorial Intermediate Current System. We found that the eastward mean flow associated with the North and South Intermediate Counter Currents (NICC and SICC, respectively) effectively shields the Equator from off-equatorial Rossby waves. The westward propagation of these waves is blocked and focusing on the Equator due to beta dispersion is prevented. This leads to less energetic jets along the Equator. On the other hand, the westward barotropic mean flow along the Equator reduces the gradient of absolute vorticity and hence widens the cross-equatorial structure of the basin mode. Increasing lateral viscosity predominantly affects the width of the basin modes’ Kelvin wave component in the presence of the mean flow while the Rossby wave is confined by the flanking NICC and SICC. Independent of the presence of the mean flow, the application of sufficient lateral mixing also hinders the focusing of off-equatorial Rossby waves, which is hence an unlikely feature of a low-frequency basin mode in the real ocean.

Description: A decadal change in the character of ENSO was observed around year 2000 toward weaker-amplitude, higher-frequency events with an increased occurrence of central Pacific El Niños. Here these changes are assessed in terms of the Bjerknes stability index (BJ index), which is a measure of the growth rate of ENSO-related SST anomalies. The individual terms of the index are calculated from ocean reanalysis products separately for the time periods 1980–99 and 2000–10. The spread between the products is large, but they show a robust weakening of the thermocline feedback due to a reduced thermocline slope response to anomalous zonal wind stress as well as a weakened wind stress response to eastern equatorial Pacific SST anomalies. These changes are consistent with changes in the background state of the tropical Pacific: cooler mean SST in the eastern and central equatorial Pacific results in reduced convection there together with a westward shift in the ascending branch of the Walker circulation. This shift leads to a weakening in the relationship between eastern Pacific SST and longitudinally averaged equatorial zonal wind stress. Also, despite a steeper mean thermocline slope in the more recent period, the thermocline slope response to wind stress anomalies weakened due to a smaller zonal wind fetch that results from ENSO-related wind anomalies being more confined to the western basin. As a result, the total BJ index is more negative, corresponding to a more strongly damped system in the past decade compared to the 1980s and 1990s.

Description: In his comment, G. Bürger criticizes the conclusion that inflation of trends by quantile mapping is an adverse effect.He assumes that the argument would be ‘‘based on the belief that long-term trends and along with them future climate signals are to be large scale.’’ His line of argument reverts to the so-called inflated regression. Here it is shown, by referring to previous critiques of inflation and standard literature in statistical modeling as well as weather forecasting, that inflation is built upon a wrong understanding of explained versus unexplained variability and prediction versus simulation. It is argued that a sound regressionbased downscaling can in principle introduce systematic local variability in long-term trends, but inflation systematically deteriorates the representation of trends. Furthermore, it is demonstrated that inflation by construction deteriorates weather forecasts and is not able to correctly simulate small-scale spatiotemporal structure.

Description: The relationship between the Agulhas Current and the Agulhas leakage is not well understood. Here, this is investigated using two basin-scale and two global ocean models, of incrementally increasing resolution. The response of the Agulhas Current is evaluated under a series of sensitivity experiments, in which idealised anomalies, designed to geometrically modulate zonal trade wind stress, are applied across the Indian Ocean basin. The imposed wind stress changes exceed ±2 standard deviations from the annual mean trade winds and, in the case of intensification, are partially representative of recently observed trends. The Agulhas leakage is quantified using complimentary techniques based on Lagrangian virtual floats and Eulerian passive tracer flux. As resolution increases, model behavior converges and the sensitivity of the leakage to Agulhas Current transport anomalies is reduced. In the two eddy-resolving configurations tested, the leakage is insensitive to changes in Agulhas Current transport at 32°S, though substantial eddy kinetic energy anomalies are evident. Consistent with observations, the position of the retroflection remains stable. The decoupling of Agulhas Current variability from the Agulhas leakage suggests that, while correlations between the two may exist, they may not have a clear dynamical basis. It is suggested that present and future Agulhas leakage proxies be considered in the context of potentially transient forcing regimes.

Description: A surface diurnal warm layer is diagnosed from Seaglider observations, and develops on half the days in the CINDY/DYNAMO Indian Ocean experiment. The diurnal warm layer occurs on days of high solar radiation flux (〉 80 W m−2) and low wind speed (〈 6 m s−1), and preferentially in the inactive stage of the Madden–Julian Oscillation. Its diurnal harmonic has an exponential vertical structure with a depth scale of 4–5 m (dependent on chlorophyll concentration), consistent with forcing by absorption of solar radiation. The effective sea surface temperature (SST) anomaly due to the diurnal warm layer often reaches 0.8°C in the afternoon, with a daily mean of 0.2°C, rectifying the diurnal cycle onto longer time scales. This SST anomaly drives an anomalous flux of 4 W m−2 that cools the ocean. Alternatively, in a climate model where this process is unresolved, this represents an erroneous flux that warms the ocean. A simple model predicts a diurnal warm layer to occur on 30–50% of days across the tropical warm pool. On the remaining days, with low solar radiation and high wind speeds, a residual diurnal cycle is observed by the Seaglider, with a diurnal harmonic of temperature that decreases linearly with depth. As wind speed increases, this already weak temperature gradient decreases further, tending towards isothermal conditions.

Description: Sea surface temperature (SST) anomalies in the eastern equatorial Atlantic are connected to modulations in the strength of the South Atlantic subtropical high-pressure system, referred to as the South Atlantic Anticyclone (SAA). Using ocean and atmosphere reanalysis products we show here that the strength of the SAA from February to May impacts the timing of the cold tongue onset and the intensity of its development in the eastern equatorial Atlantic (EEA) via anomalous tropical wind power. This modulation of the timing and amplitude of the seasonal cold tongue development manifests as anomalous SST events peaking between June and August. The timing and impact of this connection is not completely symmetric for warm and cold events. For cold events, an anomalously strong SAA in February and March leads to positive wind power anomalies from February to June resulting in an early cold tongue onset and subsequent cold SST anomalies in June and July. For warm events the anomalously weak SAA persists until May, generating negative wind power anomalies that lead to a late cold tongue onset as well as a suppression of the cold tongue development and associated warm SST anomalies. Mechanisms by which SAA induced wind power variations south of the equator influence EEA SST are discussed, including ocean adjustment via Rossby and Kelvin wave propagation, meridional advection, and local intraseasonal wind variations

Description: We present a detailed quality assessment of a novel underwater sensor for the measurement of CO2 partial pressure (pCO2) based on surface water field deployments carried out between 2008 and 2011. The commercially available sensor, which is based on membrane equilibration and NDIR spectrometry is small and can be integrated into mobile platforms. It is calibrated in water against a proven flow-through pCO2 instrument within a custom-built calibration setup. The aspect of highest concern with respect to achievable data quality of the sensor is the compensation for signal drift inevitably connected to absorption measurements. We use three means to correct for drift effects: (i) a filter correlation or dual-beam setup, (ii) regular zero gas measurements realized automatically within the sensor and (iii) a zero-based transformation of two sensor calibrations flanking the time of sensor deployment. Three sensors were tested against an underway pCO2 system during two major research cruises providing an in situ temperature range from 7.4 to 30.1°C and pCO2 values between 289 and 445 μatm. The average difference between sensor and reference pCO2 was found to be -0.6 ± 3 μatm with a RMSE of 3.7 μatm.

Description: Ammassalik in southeast Greenland is known for strong wind events that can reach hurricane intensity and cause severe destruction in the local town. Yet, these winds and their impact on the nearby fjord and shelf region have not been studied in detail. Here, data from two meteorological stations and the European Centre for Medium-Range Weather Forecasts Interim Re-Analysis (ERA-Interim) are used to identify and characterize these strong downslope wind events, which are especially pronounced at a major east Greenland fjord, Sermilik Fjord, within Ammassalik. Their local and regional characteristics, their dynamics and their impacts on the regional sea ice cover, and air–sea fluxes are described. Based on a composite of the events it is concluded that wind events last for approximately a day, and seven to eight events occur each winter. Downslope wind events are associated with a deep synoptic-scale cyclone between Iceland and Greenland. During the events, cold dry air is advected down the ice sheet. The downslope flow is accelerated by gravitational acceleration, flow convergence inside the Ammassalik valley, and near the coast by an additional thermal and synoptic-scale pressure gradient acceleration. Wind events are associated with a large buoyancy loss over the Irminger Sea, and it is estimated that they drive one-fifth of the net wintertime loss. Also, the extreme winds drive sea ice out of the fjord and away from the shelf.

Description: In 2013, the vast majority of the monitored climate variables reported here maintained trends established in recent decades. ENSO was in a neutral state during the entire year, remaining mostly on the cool side of neutral with modest impacts on regional weather patterns' around the world. This follows several years dominated by the effects of either La Nina. or El Nino events. According to several independent analyses, 2013 was again among the 10 warmest years on record at the global scale, both at the Earth's surface and through the troposphere. Some regions in the Southern Hemispherehad record or near-record high temperatures for the year. Australia observed its hottest year on record, while Argentina and New Zealand reported their second and third hottest years, respectively. In Antarctica, Amundsen-Scott South Pole Station reported its highest annual temperature since records began in 1957 At the opposite pole, the Arctic observed its seventh warmest year since record's began in the early 20th century. At 20-m depth, record high temperatures were measured at some permafrost stations on the North Slope Of Alaska and in the Brooks Range. In the Northern Hemisphere extratropics, anomalous meridional atmospheric circulation occurred throughout much of the year leading to marked regional extremes of both temperature and precipitation. Cold temperature anomalies during Winter across Eurasia were followed by warm Spring temperature anomalies, which, were linked to a new record Eurasian snow cover extent in the May. Minimum sea ice extent in the :Arctic was the sixth lowest since satellite Observations began in 1979. Including 2013, all seven lowest extents on record have occurred in the past seven years Antarctica, on the other hand, had above average sea ice extent throughout 2013, with 116 days Of new daily high extent records, inclding a new daily maximum sea ice area of 19.57 million km(2) reached on 1 October. ENSO-neutral conditions in the eastern central Pacific Ocean and a negative Pacific decadal oscillation pattern in the North Pacific had the largest impacts on the global sea surface temperature in 2013: The North Pacific reached a historic high temperature in 2013 and on balance the globally-averaged sea surface temperature was among the 10 highest on record. Overall, the salt Content in near-surface ocean waters increased while in intermediate waters it decreased. Global mean sea level continued to rise during 2013, on pace with a trend of 3,2 mm yr(-1) over the past two decades. A portion of this trend (0.5 mm yr(-1)) has been attributed to natural variability associated with the Pacific decadal oscillation as Well as to ongoing contribution from the melting of glaciers and ice sheets and ocean warming. Global tropical cyclone frequency during 2013 was slightly above average with a total of 94 storms, although the North Atlantic Basin had its quietest hurricane season since 1994. In the Western North Pacific Basin, Super Typhoon Haiyan, the deadliest tropical Cyclone of 2013, had 1-minute sustained winds estimated to be 170 kt (OS m s(-1)) on 7 November, the highest Wind speed ever assigned to a tropical cyclone. High storm surge was also associated with Haiyan at it Made landfall over the central Philippines, an area where sea level is currently at historic highs increasing by 200 mm since 1970. In the atmosphere, carbon dioxide, methane, and nitrous oxide all Continued to increase in 2013. As in previous our years, each of these Major greenhouse gases once again reached historic high Concentrations. In the Arctic carbon dioxide and methane:, Increased at the same rate as:the global increase. These increases are likely due to export from lower latitudes rather than a consequence Of increases in Arctic sources such as thawing permafrost., At Mauna Loa, Hawaii, for the first time since measurement began in 1958, the daily average Mixing ratio Of carbon dioxide exceeded 400 ppm on 9 May. The state of these variables, along with dozens of others, and the 2013 climate conditions of regions around the world are discussed in further detail in this 24th, edition of the State of the Climate series

Description: This study presents aspects of the spatial and temporal variability of abyssal water masses in the Ionian Sea, as derived from recent temperature, salinity, dissolved oxygen and velocity observations and from comparisons between these and former observations. Previous studies showed how in the Southern Adriatic Sea the Adriatic Deep Water (AdDW) became fresher (ΔS ≈ −0.08) and colder (ΔT ≈ −0.1°C) after experiencing warming and salinification between 2003 and 2007. Our data, collected from October 2009 to July 2010 from two bottom moorings, one within the Strait of Otranto and the other in the northern Ionian, confirm this tendency: a bottom vein of southward-flowing AdDW, whose temperature and salinity continuously decreased during the observation time, was detected there. Typically, the vein travel time between the two stations ranged between 45 and 50 days. This gave us a temporal estimate for AdDW anomaly propagation towards the Ionian abyss from their Adriatic generation region. The density excess of the observed vein was always enough to enable its existence as a bottom-arrested current. This evidence confirms that, at that time (2009 and 2010), the Adriatic Sea was greatly contributing to the formation of Eastern Mediterranean Deep Water (EMDW), the bottom water of the Eastern Mediterranean. Hence, based on these results and on the evidence that, from 2003 to 2009, abyssal Ionian waters became saltier and warmer under the time-lagged influence of AdDW, possible future changes in the EMDW characteristics, as a response to Adriatic variability, are discussed.

Description: The Denmark Strait Overflow (DSO) supplies about one-third of the North Atlantic Deep Water and is critical to global thermohaline circulation. Knowledge of the pathways of DSO through the Irminger Basin and its transformation there is still incomplete, however. The authors deploy over 10 000 Lagrangian particles at the Denmark Strait in a high-resolution ocean model to study these issues. First, the particle trajectories show that the mean position and potential density of dense waters cascading over the Denmark Strait sill evolve consistently with hydrographic observations. These sill particles transit the Irminger Basin to the Spill Jet section (65.25°N) in 5–7 days and to the Angmagssalik section (63.5°N) in 2–3 weeks. Second, the dense water pathways on the continental shelf are consistent with observations and particles released on the shelf in the strait constitute a significant fraction of the dense water particles recorded at the Angmagssalik section within 60 days (~25%). Some particles circulate on the shelf for several weeks before they spill off the shelf break and join the overflow from the sill. Third, there are two places where the water density following particle trajectories decreases rapidly due to intense mixing: to the southwest of the sill and southwest of the Kangerdlugssuaq Trough on the continental slope. After transformation in these places, the overflow particles exhibit a wide range of densities.

Description: Quantile mapping is routinely applied to correct biases of regional climate model simulations compared to observational data. If the observations are of similar resolution as the regional climate model, quantile mapping is a feasible approach. However, if the observations are of much higher resolution, quantile mapping also attempts to bridge this scale mismatch. Here, it is shown for daily precipitation that such quantile mapping-based downscaling is not feasible but introduces similar problems as inflation of perfect prognosis ("prog") downscaling: the spatial and temporal structure of the corrected time series is misrepresented, the drizzle effect for area means is overcorrected, area-mean extremes are overestimated, and trends are affected. To overcome these problems, stochastic bias correction is required.

Description: Previous attempts to derive the depth-dependent expression of the radiation stress have lead to a debate concerning (i) the applicability of Mellor’s approach to a sloping bottom, (ii) the introduction of the delta function at the mean sea surface in the later papers by Mellor, and (iii) a wave-induced pressure term derived in several recent studies. The authors use an equation system in vertically Lagrangian and horizontally Eulerian (VL) coordinates suitable for a concise treatment of the surface boundary, and obtain an expression for the depth-dependent radiation stress that is consistent with the vertically-integrated expression given by Longuet-Higgins and Stewart. Concerning (i)-(iii) in the above, the difficulty of handling a sloping bottom disappears when wave-averaged momentum equations in the VL coordinates are written for the development of (not the Lagrangian mean velocity but) the Eulerian mean velocity. There is also no delta function at the sea surface in the expression for the depth-dependent radiation stress. The connection between the wave-induced pressure term in the recent studies and the depth-dependent radiation stress term is easily shown by rewriting the pressure-based form stress term in the thickness-weighted-mean (TWM) momentum equations as a velocity-based term which contains the time derivative of the pseudomomentum in the TWM framework.

Description: The upper ocean, including the biologically productive euphotic zone and the mixed layer, has great relevance for studies of physical, biogeochemical, and ecosystem processes and their interaction. Observing this layer with a continuous presence, sampling many of the relevant variables, and with sufficient vertical resolution, has remained a challenge. Here a system is presented which can be deployed on the top of deep-ocean moorings, with a drive mechanism at depths of 150-200m, which mechanically winches a large sensor float and smaller communications float tethered above it to the surface and back down again, typically twice per day for periods up to 1 year. The sensor float can carry several sizeable sensors, and it has enough buoyancy to reach the near surface and for the communications float to pierce the surface even in the presence of strong currents. The system can survive mooring blow-over to 1000m depth. The battery-powered design is made possible by using a balanced energy-conserving principle. Reliability is enhanced with a drive assembly that employs a single rotating part that has no slip rings or rotating seals. The profiling bodies can break the surface to sample the near-surface layer and to establish satellite communication for data relay or reception of new commands. An inductive pass-through mode allows communication with other mooring components throughout the water column beneath the system. A number of successful demonstration deployments have been completed.

Description: In recent years, profiling floats, which form the basis of the successful international Argo observatory, are also being considered as platforms for marine biogeochemical research. This study showcases the utility of floats as a novel tool for combined gas measurements of CO2 partial pressure (pCO2) and O2. These float prototypes were equipped with a small-sized and submersible pCO2 sensor and an optode O2 sensor for high resolution measurements in the surface ocean layer. Four consecutive deployments were carried out during Nov. 2010 and June 2011 near the Cape Verde Ocean Observatory (CVOO) in the eastern tropical North Atlantic. The profiling float performed upcasts every 31 h while measuring pCO2, O2, salinity, temperature and hydrostatic pressure in the upper 200 m of the water column. In order to maintain accuracy, regular pCO2 sensor zeroings at depth and surface, as well as optode measurements in air, were performed for each profile. Through the application of data processing procedures (e.g., time-lag correction) accuracies of float-borne pCO2 measurements were greatly improved (10 – 15 μatm for water column and 5 μatm for surface measurements). O2 measurements yielded an accuracy of 2 μmol kg−1. First results of this pilot study show the possibility of using profiling floats as a platform for detailed and unattended observations of the marine carbon and oxygen cycle dynamics.

Description: The use of a coupled ocean/atmosphere/sea-ice model to hindcast (i.e. historical forecast) recent climate variability is described and illustrated for the cases of the 1976/77 and 1998/99 climate shift events in the Pacific. The initialization is achieved by running the coupled model in partially coupled mode whereby global observed wind stress anomalies are used to drive the ocean/sea-ice component of the coupled model while maintaining the thermodynamic coupling between the ocean/sea-ice and atmosphere components. Here we show that hindcast experiments can successfully capture many features associated with the 1976/77 and 1998/99 climate shifts. For instance, hindcast experiments started from the beginning of 1976 can capture sea surface temperature (SST) warming in the central-eastern equatorial Pacific and the positive phase of the Pacific Decadal Oscillation (PDO) throughout the 9 years following the 1976/77 climate shift, including the deepening of the Aleutian low pressure system. Hindcast experiments started from the beginning of 1998 can also capture part of the anomalous conditions during the 4 years after the 1998/99 climate. We argue that the dynamical adjustment of heat content anomalies that are present in the initial conditions in the tropics is important for the successful hindcast of the two climate shifts.

Description: One of the most remarkable features of the reproductive systems of eubrachyuran crabs is the presence of specialized organs for sperm storage, the seminal receptacles. Descriptions of seminal receptacle morphology, sperm storage time, sperm retention across molts, and the capacity to store multiple ejaculates from different males can help in understanding crab mating strategies as well as in preventing negative effects of male-biased fisheries of heavily harvested species. Metacarcinus edwardsii is the most harvested crab in Chile, but its reproductive biology is largely unstudied. In this study, the morphology of the seminal receptacles of M. edwardsii is characterized from the macroscopic to the microscopic level, during key points in the reproductive cycle. The receptacles of experimentally mated and wild-caught females were included in this analysis. Metacarcinus edwardsii has ventral-type seminal receptacles that are able to retain sperm after molting, and even after extrusion of the eggs. Stratification of multiple ejaculates is clearly observed. In general, the pattern of sperm storage indicates that populations of this species, like those of other cancrid crabs, could have high resilience to the negative effects of the selective harvest of males, principally because females have a great sperm storage capacity.

Description: The Arctic continental shelf seas hold a globally significant source of freshwater that impacts Arctic Ocean stratification, circulation, and climate. This freshwater can be injected below the surface mixed layer by intense turbulent kinetic energy dissipation events, as resolved by Laptev Sea microstructure observations. The tides provide a major source of energy that can be dissipated and hence drive diapycnal mixing in the Laptev Sea. Multiyear ADCP mooring records from locations across the shelf reveal that semidiurnal tides are dominated by theM2 and S2 constituents, with the largest amplitudes on the outer shelf. Throughoutmost of the shelf, tides are clockwise polarized and sheared by stratification, as characteristic near the M2 critical latitude. Interannual variations of the tidal and shear structures on the inner shelf aremainly determined by the stratification-setting Lena River freshwater plume. In all locations,M2 tides are enhanced under sea ice, and therefore changes in the seasonal ice cover may lead to changes in tides and water column structure. The main conclusions of this study are that (i) tides play a comparatively greater role year-round on the outer shelf relative to the inner shelf; (ii) a sea ice reduction will overall decrease the predictability of the currents, especially on the inner shelf; and (iii) the freshwater distribution directly impacts diapycnal mixing by setting the vertical tidal structure. These combined effects imply that future sea ice loss will increase the variability and vertical mixing of freshwater, particularly on the inner shelf, where the Lena River first enters the Laptev Sea.

Description: El Niño–Southern Oscillation (ENSO) in the Pacific and the analogous Atlantic Niño mode are generated by processes involving coupled ocean–atmosphere interactions known as the Bjerknes feedback. It has been argued that the Atlantic Niño mode is more strongly damped than ENSO, which is presumed to be closer to neutrally stable. In this study the stability of ENSO and the Atlantic Niño mode is compared via an analysis of the Bjerknes stability index. This index is based on recharge oscillator theory and can be interpreted as the growth rate for coupled modes of ocean–atmosphere variability. Using observational data, an ocean reanalysis product, and output from an ocean general circulation model, the individual terms of the Bjerknes index are calculated for the first time for the Atlantic and then compared to results for the Pacific. Positive thermocline feedbacks in response to wind stress forcing favor anomaly growth in both basins, but they are twice as large in the Pacific compared to the Atlantic. Thermocline feedback is related to the fetch of the zonal winds, which is much greater in the equatorial Pacific than in the equatorial Atlantic due to larger basin size. Negative feedbacks are dominated by thermal damping of sea surface temperature anomalies in both basins. Overall, it is found that both ENSO and the Atlantic Niño mode are damped oscillators, but the Atlantic is more strongly damped than the Pacific primarily because of the weaker thermocline feedback.

Description: A large number of quantities have to be measured and processed to determine the atmospheric-state variables, which are the actual measurands, from aircraft-based measurements. A great part of the dependencies between these quantities depends on the aerodynamic state of the aircraft. Aircraft-based meteorological measurements, hence, require in-flight calibration. Most operators of research aircraft perform some kind of calibration, but the schemes used and the degree they are documented greatly vary. The flight maneuvers and calculation methods required, however, are published in a number of partly overlapping and partly contradictory publications. Some methods are only presented as a minor issue in publications mainly focused on atmospheric processes and are therefore hard to find. For an aircraft user, it is hence challenging to either perform or verify a calibration because of missing comprehensive guidance. This lack was stated on occasion of the in-flight calibration of the German research aircraft Polar5 carried out for the field experiment Investigation of Katabatic Winds and Polynyas during Summer (IKAPOS). In the present paper, a comprehensive review of the existing literature on this field and a practical guide to the wind calibration of a research aircraft to be used for turbulent flux measurements are given.

Description: A monthly, isopycnal/mixed-layer ocean climatology (MIMOC), global from 0 to 1950 dbar, is compared with other monthly ocean climatologies. All available quality-controlled profiles of temperature (T) and salinity (S) versus pressure (P) collected by conductivity-temperature-depth (CTD) instruments from the Argo Program, Ice-Tethered Profilers, and archived in the World Ocean Database are used. MIMOC provides maps of mixed layer properties (conservative temperature, Θ, absolute salinity, SA, and maximum P) as well as maps of interior ocean properties (Θ, SA, and P) to 1950 dbar on isopycnal surfaces. A third product merges the two onto a pressure grid spanning the upper 1950 dbar, adding more familiar potential temperature (θ) and practical salinity (S) maps. All maps are at monthly 0.5° × 0.5° resolution, spanning from 80°S to 90°N. Objective mapping routines used and described here incorporate an isobath-following component using a “Fast Marching” algorithm, as well as front-sharpening components in both the mixed layer and on interior isopycnals. Recent data are emphasized in the mapping. The goal is to compute a climatology that looks as much as possible like synoptic surveys sampled circa 2007–2011 during all phases of the seasonal cycle, minimizing transient eddy and wave signatures. MIMOC preserves a surface mixed layer, minimizes both diapycnal and isopycnal smoothing of θ-S, as well as preserves density structure in the vertical (pycnoclines and pycnostads) and the horizontal (fronts and their associated currents). It is statically stable and resolves water mass features, fronts, and currents with a high level of detail and fidelity.

Description: Accurate projections of stratospheric ozone are required because ozone changes affect exposure to ultraviolet radiation and tropospheric climate. Unweighted multimodel ensemble-mean (uMMM) projections from chemistry–climate models (CCMs) are commonly used to project ozone in the twenty-first century, when ozone-depleting substances are expected to decline and greenhouse gases are expected to rise. Here, the authors address the question of whether Antarctic total column ozone projections in October given by the uMMM of CCM simulations can be improved by using a process-oriented multiple diagnostic ensemble regression (MDER) method. This method is based on the correlation between simulated future ozone and selected key processes relevant for stratospheric ozone under present-day conditions. The regression model is built using an algorithm that selects those process-oriented diagnostics that explain a significant fraction of the spread in the projected ozone among the CCMs. The regression model with observed diagnostics is then used to predict future ozone and associated uncertainty. The precision of the authors’ method is tested in a pseudoreality; that is, the prediction is validated against an independent CCM projection used to replace unavailable future observations. The tests show that MDER has higher precision than uMMM, suggesting an improvement in the estimate of future Antarctic ozone. The authors’ method projects that Antarctic total ozone will return to 1980 values at around 2055 with the 95% prediction interval ranging from 2035 to 2080. This reduces the range of return dates across the ensemble of CCMs by about a decade and suggests that the earliest simulated return dates are unlikely.

Description: Evidence is presented for the notion that some contribution to the recent decadal trends observed in the Southern Hemisphere, including the lack of a strong Southern Ocean surface warming, may have originated from longer-term internal centennial variability originating in the Southern Ocean. The existence of such centennial variability is supported by the instrumental sea surface temperatures (SSTs), a multimillennial reconstruction of Tasmanian summer temperatures from tree rings, and a millennial control integration of the Kiel Climate Model (KCM). The model variability was previously shown to be linked to changes in Weddell Sea deep convection. During phases of deep convection the surface Southern Ocean warms, the abyssal Southern Ocean cools, Antarctic sea ice extent retreats, and the low-level atmospheric circulation over the Southern Ocean weakens. After the halt of deep convection the surface Southern Ocean cools, the abyssal Southern Ocean warms, Antarctic sea ice expands, and the low-level atmospheric circulation over the Southern Ocean intensifies, consistent with what has been observed during the recent decades. A strong sensitivity of the time scale to model formulation is noted. In the KCM, the centennial variability is associated with global-average surface air temperature (SAT) changes of the order of a few tenths of a degree per century. The model results thus suggest that internal centennial variability originating in the Southern Ocean should be considered in addition to other internal variability and external forcing when discussing the climate of the twentieth century and projecting that of the twenty-first century.

Description: The wintertime northern annular mode (NAM) at the surface is known to undergo slow intraseasonal variations in association with stratospheric variability, which leads the surface signal by up to several weeks. The relative contributions, however, of potentially relevant stratosphere–troposphere coupling mechanisms are not yet fully understood. In this study the relative roles of (i) the downward effect of the zonal-mean secondary circulation induced by quasigeostrophic (QG) adjustment to stratospheric wave drag and radiative damping and (ii) wave drag local to the troposphere are estimated. For this purpose, a spectral tendency equation of the QG zonal-mean zonal wind is derived and used, in a first step, to obtain the external mechanical forcing that, in the QG framework, drives exactly the observed stratospheric and tropospheric daily NAM. In a second step, the equation is then integrated in time to reconstruct the daily NAM, but with the forcing restricted to either stratospheric or tropospheric levels, each case leaving a characteristic NAM surface signal. The relative roles of the above-mentioned mechanisms are found to be of similar quantitative importance, but to differ in a qualitative sense. The downward effect of stratospheric QG adjustment is responsible for the initiation of the NAM surface signal, whereas subsequently local tropospheric wave drag actively maintains and persists the signal over several weeks. Furthermore, the downward effect of QG adjustment to stratospheric radiative damping is shown to have only a minor impact, compared to that from stratospheric wave drag. The robustness of these conclusions is demonstrated by a sensitivity study with respect to various model parameters.

Description: The Agulhas Current plays a crucial role in the thermohaline circulation through its leakage into the South Atlantic. Under both past and present climates, the trade winds and westerlies could have the ability to modulate the amount of Indian-Atlantic inflow. Compelling arguments have been put forward suggesting that trade winds alone have little impact on the magnitude of Agulhas leakage. Here, employing three ocean models for robust analysis – a global coarse resolution, a regional eddy-permitting and a nested high-resolution eddy-resolving configuration – and systematically altering the position and intensity of the westerly wind belt in a series of sensitivity experiments, it is shown that the westerlies, in particular their intensity, control the leakage. Leakage responds proportionally to the westerlies intensity up to a certain point. Beyond this, through the adjustment of the large-scale circulation, energetic interactions occur between the Agulhas Return Current and the Antarctic Circumpolar Current that result in a state where leakage no longer increases. This adjustment takes place within 1 to 2 decades. Contrary to previous assertions, our results further show that an equatorward (poleward) shift in westerlies increases (decreases) leakage. This occurs due to the redistribution of momentum input by the winds. It is concluded that the reported present-day leakage increase could therefore reflect an unadjusted oceanic response mainly to the strengthening westerlies over the last few decades.

Description: For the first time in serveral years, the El Nino-Southern Oscillation did not dominate regional climate conditions around the globe. A weak La Ni a dissipated to ENSOneutral conditions by spring, and while El Nino appeared to be emerging during summer, this phase never fully developed as sea surface temperatures in the eastern conditions. Nevertheless, other large-scale climate patterns and extreme weather events impacted various regions during the year. A negative phase of the Arctic Oscillation from mid-January to early February contributed to frigid conditions in parts of northern Africa, eastern Europe, and western Asia. A lack of rain during the 2012 wet season led to the worst drought in at least the past three decades for northeastern Brazil. Central North America also experienced one of its most severe droughts on record. The Caribbean observed a very wet dry season and it was the Sahel's wettest rainy season in 50 years. Overall, the 2012 average temperature across global land and ocean surfaces ranked among the 10 warmest years on record. The global land surface temperature alone was also among the 10 warmest on record. In the upper atmosphere, the average stratospheric temperature was record or near-record cold, depending on the dataset. After a 30-year warming trend from 1970 to 1999 for global sea surface temperatures, the period 2000-12 had little further trend. This may be linked to the prevalence of La Ni a-like conditions during the 21st century. Heat content in the upper 700 m of the ocean remained near record high levels in 2012. Net increases from 2011 to 2012 were observed at 700-m to 2000-m depth and even in the abyssal ocean below. Following sharp decreases in to the effects of La Ni a, sea levels rebounded to reach records highs in 2012. The increased hydrological cycle seen in recent years continued, with more evaporation in drier locations and more precipitation in rainy areas. In a pattern that has held since 2004, salty areas of the ocean surfaces and subsurfaces were anomalously salty on average, while fresher areas were anomalously fresh. Global tropical cyclone activity during 2012 was near average, with a total of 84 storms compared with the 1981-2010 average of 89. Similar to 2010 and 2011, the North Atlantic was the only hurricane basin that experienced above-normal activity. In this basin, Sandy brought devastation to Cuba and parts of the eastern North American seaboard. All other basins experienced either near-or below-normal tropical cyclone activity. Only three tropical cyclones reached Category 5 intensity-all in Bopha became the only storm in the historical record to produce winds greater than 130 kt south of 7 N. It was also the costliest storm to affect the Philippines and killed more than 1000 residents. Minimum Arctic sea ice extent in September and Northern Hemisphere snow cover extent in June both reached new record lows. June snow cover extent is now declining at a faster rate (-17.6% per decade) than September sea ice extent (-13.0% per decade). Permafrost temperatures reached record high values in northernmost Alaska. A new melt extent record occurred on 11-12 July on the Greenland ice sheet; 97% of the ice sheet showed some form of melt, four times greater than the average melt for this time of year. The climate in Antarctica was relatively stable overall. The largest maximum sea ice extent since records begain in 1978 was observed in September 2012. In the stratosphere, warm air led to the second smallest ozone hole in the past two decades. Even so, the springtime ozone layer above Antarctica likely will not return to its early 1980s state until about 2060. Following a slight decline associated with the global 2 emissions from fossil fuel combustion and cement production reached a record 9.5 +/- 0.5 Pg C in 2011 and a new record of 9.7 +/- 0.5 Pg C is estimated for 2012. Atmospheric CO2 concentrations increased by 2.1 ppm in 2012, to 392.6 ppm. In spring 2012, 2 concentration exceeded 400 ppm at 7 of the 13 Arctic observation sites. Globally, other greenhouse gases including methane and nitrous oxide also continued to rise in concentration and the combined effect now represents a 32% increase in radiative forcing over a 1990 baseline. Concentrations of most ozone depleting substances continued to fall.

Description: The feeding habits of the pelagic stingray ( Pteroplatytrygon violacea ) were studied using 84 stomachs of specimens caught in the northern Adriatic Sea in the period from April 2004 to October 2005. Percentage of empty stomachs found was overall very low, being a bit bigger in smaller specimens. The diet consisted of two main taxonomic groups such as teleost fish and cephalopods, but few specimens of crustaceans were recorded as well. The main food item was represented by anchovy, while cuttlefish and red band fish represented the alternative preys. Prey size was positively correlated with the size of predator. The proportion of anchovies in the diet grew with size of predator, while the one for red band fish decreased. The stingray was confirmed to be a top predator of pelagic fish species, although the presence of benthic prey shows that it feeds also at the bottom.

Description: The schooling behaviour of the oval squid Sepioteuthis lessoniana was observed over 4 summers at 3 observation sites in the coastal waters of Okinawa Island, Ryukyu Archipelago, Japan. During this field study, 3 static appearances (belt, ball and sheet shape) and 2 transitional appearances (high and low density) were noted, recorded and described. In addition to formations, a member of S. lessoniana schools also displayed particular and repeated behavioural patterns such as vanguard and intimidating display. The 3 observation sites were tropical coral reefs near the coastline at a depth of 1 to 15 m on an average. All participating observers snorkelled and were equipped with various underwater digital video and photographic cameras. The schools observed consisted of 8 to over 100 members with a wide range of body sizes. Despite these biological and locational differences, both static and transitional appearances were consistently observed with equally consistent individual behavioural patterns. There have been studies on related species, Sepioteuthis sepioidea, at the San Blas Islands along the Caribbean coast of eastern Panama, and the same species, S. lessoniana, at a different geographical location, Casuarina Beach on Lizard Island, Australia. The findings of this study are consistent with those reported previously, with some notable differences.

Description: Age structure and hatchling dates of the squid Illex argentinus collected by bottom-trawl fishery in southern Brazilian waters were assessed by the analysis of statolith growth increments. Catches occurred between 2001 and 2002, from 23° to 32°S at depths of 100–700 m. Squid from juvenile to post-spawning stages were collected year round, with age estimated from 98 to 320 days and mantle lengths ranging from 112 to 376 mm. Duration of life cycle events based on statolith growth zones revealed that squids can spend about 14% of their lifespan as paralarva (~30 days), 70% as juvenile (~130 days), leaving maturity and spawning condition to the terminal 10–20% (~30–60 days). The results suggest that, unlike estimates available for Patagonian populations, a general 0.5 year lifespan is predicted for I. argentinus off Brazil. The wide range of size-at-ages implied that catches of shortfin squid off southern Brazil probably include squid hatched throughout the year. Mature and spawning squid caught in summer months hatched in winter and spring, while winter catches revealed mature-spawning individuals hatched both in summer/autumn (~6 months of age) and winter/spring periods (~10–11 months of age). It has been argued that such groups may combine both squid resident of Brazilian outer shelf and slope (22°–34°S) with a six months' lifespan and migrating squid originated from the northern Patagonian shelf (~42°S) with 10–11 months' lifespan.

Description: Mesoscale anticyclonic eddies in the Irminger Sea are observed using a mooring and a glider. Between 2002 and 2009, the mooring observed 53 anticyclones. Using a kinematic model, objective estimates of eddy length scales and velocity structure are made for 16 eddies. Anticyclones had a mean core diameter of 12 km, and their mean peak observed azimuthal speed was 0.1 m s(-1). They had core salinities and potential temperatures of 34.91-34.98 and 4.488-5.34 degrees C, respectively, making them warm and salty features. These properties represent a typical salinity anomaly of 0.03 and a temperature anomaly of 0.28 degrees C from noneddy values. All eddies had small (〈〈 1) Rossby numbers. In 2006, the glider observed two anticyclones having diameters of about 20 km and peak azimuthal speeds of about 0.3 m s(-1). Similar salinity anomalies were detected throughout the Irminger Sea by floats profiling in anticyclones. Two formation regions for the eddies are identified: one to the west of the Reykjanes Ridge and the other off the East Greenland Irminger Current near Cape Farewell close to the mooring. Observations indicate that eddies formed in the former region are larger than eddies observed at the mooring. A clear increase in eddy salinity is observed between 2002 and 2009. The observed breakup of these eddies in winter implies that they are a source of salt for the central gyre. The anticyclones are similar to those found in both the Labrador Sea and Norwegian Sea, making them a ubiquitous feature of the subpolar North Atlantic basins.

Description: In this article we address the causes of the large-scale tropical sea level pressure (SLP) changes during climate change. The analysis we present is based on model simulations, observed trends and the seasonal cycle. In all three cases the regional changes of tropospheric temperature (Ttropos) and SLP are strongly related to each other (considerably stronger than (sea) surface temperature and SLP). This relationship basically follows the Bjerknes Circulation Theorem, with relatively low regional SLP where we have relatively high Ttropos and vice versa. A simple physical model suggests a tropical SLP response to horizontally inhomogeneous warming in the tropical Ttropos, with a sensitivity coefficient of about -1.7 hPa/K. This relationship explains a large fraction of observed and predicted changes in the tropical SLP. It is shown that in climate change model simulations the tropospheric land-sea warming contrast is the most significant structure in the regional Ttropos changes relative to the tropical mean changes. Since the land-sea warming contrast exists in the absent of any atmospheric circulation changes it can be argued that the large-scale response of tropical SLP changes is to first order a response to the tropical land-sea warming contrast. Further, as land-sea warming contrast is mostly available moisture dependent, the models predict a stronger warming and decreasing SLP in the drier regions from South America to Africa and a weaker warming and increasing SLP over the wetter Indo-Pacific warm pool region. This suggests an increase in the potential for deep convection conditions over the Atlantic Sector and a decrease over the Indo-Pacific warm pool region in the future.

Description: Variations in eastern Indian Ocean upper-ocean thermal properties are assessed for the period 1970–2004, with a particular focus on asymmetric features related to opposite phases of Indian Ocean Dipole events, using high-resolution ocean model hindcasts. Sensitivity experiments, where atmospheric forcing variability is restricted to the Indian or Pacific Ocean only, support the interpretation of forcing mechanisms for large-scale asymmetric behavior in eastern Indian Ocean variability. Years are classified according to eastern Indian Ocean subsurface heat content (HC) as proxy of thermocline variations. Years characterized by anomalous low HC feature a zonal gradient in upper-ocean properties near the equator, while high events have a meridional gradient from the tropics into the subtropics. The spatial and temporal characteristics of the seasonal evolution of HC anomalies for the two cases is distinct, as is the relative contribution from Indian Ocean atmospheric forcing versus remote influences from Pacific wind forcing: low events develop rapidly during austral winter/spring in response to Indian Ocean wind forcing associated with an enhanced southeasterly monsoon driving coastal upwelling and a shoaling thermocline in the east; in contrast, formation of anomalous high eastern Indian Ocean HC is more gradual, with anomalies earlier in the year expanding from the Indonesian Throughflow (ITF) region, initiated by remote Pacific wind forcing and transmitted through the ITF via coastal wave dynamics. Implications for seasonal predictions arise with high HC events offering extended lead times for predicting thermocline variations and upper-ocean properties across the eastern Indian Ocean.

Description: European Polar Low Working Group This workshop summarized the current state of PL research in the Arctic and Antarctic. A couple of related projects are in the planning phase or already funded. The creation of a PL database for the Norwegian Sea in the frame of the Sea Surface Temperature and Altimeter Synergy (STARS) project (http://projects.met.no stars) will provide a valuable resource for future research and, potentially, predictability improvements. The maintenance of this database and the creation of similar databases for other polar areas including satellite and NWP data are highly recommended. There is also a need for free and timely access to satellite data, in particular to SAR data to fill the gap caused by the mission end of Envisat. With the increasing resolution of climate models, mesoscale processes such as polar MCs will have to be considered in international research programs such as the World Climate Research Programme (WCRP) Polar Climate Predictability Initiative and the World Weather Research Programme (WWRP) Polar Predictability Project.

Description: Four major NE trending postglacial volcanic and tectonic fissure swarms (volcanic systems) occur on the Reykjanes Peninsula, and the westernmost three are the main subject of this paper. Two main types of basaltic volcanoes are associated with these systems: shields of picrite and olivine tholeiite and tholeiite fissures. The average volume of 26 shields is 1.11 km3, and the total production is 29 km3, whereas the corresponding figures for lavas from 101 volcanic fissures are 0.11 km3 and 11 km3. The tectonic fractures are either tension fractures or normal faults of widths up to 20 m, throws up to 10 m, and lengths up to several kilometers. The volcanism and tectonics can be explained by magmatic pressure changes in ellipsoidal magma reservoirs located beneath the fissure swarms. A magmatic pressure increase of the order of 10 MPa is found to be sufficient for an excess uplift of the order of several meters, which is all that is needed to account for the fractures and measured dilation in the fissure swarms. It is concluded that most shield volcanoes, in particular the picrite shields and the large olivine tholeiite shields, formed during the early postglacial period and that their formation was facilitated by the stress field generated as a result of rapid uplift and bending of the crust above the reservoirs. Since that time the reservoirs have become independent systems, the volcanism has been confined to fissures, and the production rate has decreased significantly. During typical fissure eruptions (0.015 km3), only the uppermost several hundred meters of the source reservoir, depending on its magma content, supply magma to the eruption.

Description: The mechanisms involved in setting the annual cycle of the Florida Current transport are revisited using an adjoint model approach. Adjoint sensitivities of the Florida Current transport to wind stress reproduce a realistic seasonal cycle with an amplitude of ~1.2 Sv (1 Sv ≡ 106 m3 s−1). The annual cycle is predominantly determined by wind stress forcing and related coastal upwelling (downwelling) north of the Florida Strait along the shelf off the North American coast. Fast barotropic waves propagate these anomalies southward and reach the Florida Strait within a month, causing an amplitude of ~1 Sv. Long baroclinic planetary Rossby waves originating from the interior are responsible for an amplitude of ~0.8 Sv but have a different phase. The sensitivities corresponding to the first baroclinic mode propagate westward and are highly influenced by topography. Considerable sensitivities are only found west of the Mid-Atlantic Ridge, with maximum values at the western shelf edge. The second baroclinic mode also has an impact on the Florida Current variability, but only when a mean flow is present. A second-mode wave train propagates southwestward from the ocean bottom on the western side of the Mid-Atlantic Ridge between ~36° and 46°N and at Flemish Cap, where the mean flow interacts with topography, to the surface. Other processes such as baroclinic waves along the shelf and local forcing within the Florida Strait are of minor importance.

Description: The residual effect of surface gravity waves on mean flows in the upper ocean is investigated using thickness weighted mean (TWM) theory applied in a vertically Lagrangian and horizontally Eulerian coordinate system. Depth-dependent equations for the conservation of volume, momentum, and energy are derived. These equations allow for (i) finite amplitude fluid motions, (ii) the horizontal divergence of currents and (iii) a concise treatment of both the kinematic and viscous boundary conditions at the sea surface. Under the assumptions of steady and monochromatic waves and a uniform turbulent viscosity, the TWM momentum equations are used to illustrate the pressure- and viscosity-induced momentum fluxes through the surface that are implicit in previous studies of the wave-induced modification of the classical Ekman spiral problem. The TWM approach clarifies, in particular, the surface momentum flux associated with the so-called virtual wave stress of Longuet-Higgins. Overall the TWM framework can be regarded as an alternative to the three-dimensional Lagrangian mean framework of Pierson. Moreover the TWM framework can be used to include the residual effect of surface waves in large-scale circulation models. In specific models that carry the TWM velocity appropriate for advecting tracers as their velocity variable, the turbulent viscosity term should be modified so that the viscosity acts only on the Eulerian mean velocity.

Description: Many aspects of barnacle body form are known to be developmentally plastic. Perhaps the most striking examples of such plasticity occur in their feeding legs and unusually long penises, the sizes and shapes of which can change dramatically and adaptively with changes in conspecific density and local water flow conditions. However, whether variation in overall appendage form is mirrored by structural responses in cuticle and muscle is not known. In order to determine how structural variation underlies phenotypic plasticity in barnacle appendages, we examined barnacles occurring at low and high population densities from one wave-protected and one wave-exposed site. We used histological sectioning and fluorescence microscopy of feeding legs and penises to compare cuticle thickness, muscle thickness, and muscle organization, and artificial penis inflation to compare penis extensibility. We observed striking differences in cuticle thickness, muscle thickness, and muscle organization between sites that differed in water velocity, but we found no clear differences associated with variation in conspecific density. Penis extensibility also did not differ consistently between sites. These results are consistent with an adaptive explanation for much of the remarkable and complex variation in barnacle feeding leg and penis morphology among sites that differ in water velocity.

Description: The Denmark Strait overflow provides about half of the total dense water overflow from the Nordic Seas into the North Atlantic Ocean. The velocity of the overflow has been monitored in the Strait with two moored Acoustic Doppler Current Profilers since 1996 with several interruptions due to mooring losses or instrument failure. So far, overflow transports were only calculated when data from both moorings were available. In this work, we introduce a linear model to fill gaps in the time series when data from only one instrument is available. The mean overflow transport is 3.4 Sv and exhibits a variance of 2.0 Sv2. No significant trend was detected in the time series. The highest variability in the transport is associated with the passage of mesoscale eddies with time scales of 2–10 days (associated with a variance of 1.5 Sv2). Seasonal variability is weak and explains less than 5% of the variance in all time series, which is in contrast to the strong seasonal cycle found in high resolution model simulations. Interannual variability is on the order of 10% of the mean. A relation to atmospheric forcing such as the local wind stress curl, as well as to larger scale phenomena, e.g. the North Atlantic Oscillation, is not detected. Since 2005 data from moored temperature, conductivity and pressure recorders have been available as well, monitoring the hydrographic variability at the bottom of Denmark Strait. In recent years the temperature time series of the Denmark Strait overflow revealed a cooling, while the salinity stayed nearly constant.

Description: Large-scale budget calculations and numerical model process studies suggest that lateral eddy heat fluxes have an important cooling effect on the Norwegian Atlantic Current (NwAC) as it flows through the Nordic Seas. But observational estimates of such fluxes have been lacking. Here, wintertime surface eddy heat fluxes in the eastern Nordic Seas are estimated from surface drifter data, satellite data and an eddy-permitting numerical model. Maps of the eddy heat flux divergence suggest advective cooling along the path of the NwAC. Integrating the flux divergence over temperature classes yields consistent estimates for the three data sets; the waters warmer than about 6°C are cooled while the cooler waters are warmed. Similar integrations over bottom depth classes show that regions shallower than about 2000 m are cooled while deeper regions are warmed. Finally, integrating the flux divergence along the core of the NwAC suggests that the highest eddy-induced heat loss at the surface is along the steepest part of the continental slope, east of the Lofoten Basin. The model fields indicate that cooling of the current by lateral eddy fluxes is comparable to or larger than the local heat loss to the atmosphere.

Description: On 12 September 2007, an Mw8.4 earthquake occurred within the southern section of the Mentawai segment of the Sumatra subduction zone, where the subduction thrust had previously ruptured in 1833 and 1797. Traveltime data obtained from a temporary local seismic network, deployed between December 2007 and October 2008 to record the aftershocks of the 2007 event, was used to determine two-dimensional (2-D) and three-dimensional (3-D) velocity models of the Mentawai segment. The seismicity distribution reveals significant activity along the subduction interface and within two clusters in the overriding plate either side of the forearc basin. The downgoing slab is clearly distinguished by a dipping region of highVp (8.0 km/s), which can be a traced to ∼50 km depth, with an increased Vp/Vs ratio (1.75 to 1.90) beneath the islands and the western side of the forearc basin, suggesting hydrated oceanic crust. Above the slab, a shallow continental Moho of less than 30 km depth can be inferred, suggesting that the intersection of the continental mantle with the subducting slab is much shallower than the downdip limit of the seismogenic zone despite localized serpentinization being present at the toe of the mantle wedge. The outer arc islands are characterized by low Vp (4.5–5.8 km/s) and high Vp/Vs (greater than 2.0), suggesting that they consist of fluid saturated sediments. The very low rigidity of the outer forearc contributed to the slow rupture of the Mw 7.7 Mentawai tsunami earthquake on 25 October 2010.

Description: The tropical Atlantic wind response to El Niño forcing is robust, with weakened northeast trade winds north of the equator and strengthened southeast trade winds along and south of the equator. However, the relationship between sea surface temperature (SST) anomalies in the eastern equatorial Pacific and Atlantic is inconsistent, with El Niño events followed sometimes by warm and other times by cold boreal summer anomalies in the Atlantic cold tongue region. Using observational data and a hindcast simulation of the Nucleus for European Modeling of the Ocean (NEMO) global model at 0.5° resolution (NEMO-ORCA05), this inconsistent SST relationship is shown to be at least partly attributable to a delayed negative feedback in the tropical Atlantic that is active in years with a warm or neutral response in the eastern equatorial Atlantic. In these years, the boreal spring warming in the northern tropical Atlantic that is a typical response to El Niño is pronounced, setting up a strong meridional SST gradient. This leads to a negative wind stress curl anomaly to the north of the equator that generates downwelling Rossby waves. When these waves reach the western boundary, they are reflected into downwelling equatorial Kelvin waves that reach the cold tongue region in late boreal summer to counteract the initial cooling that is due to the boreal winter wind stress response to El Niño. In contrast, this initial cooling persists or is amplified in years in which the boreal spring northern tropical Atlantic warming is weak or absent either because of a positive North Atlantic Oscillation (NAO) phase or an early termination of the Pacific El Niño event.

Description: Initial-value predictability measures the degree to which the initial state can influence predictions. In this paper, the initial-value predictability of six atmosphere–ocean general circulation models in the North Pacific and North Atlantic is quantified and contrasted by analyzing long control integrations with time invariant external conditions. Through the application of analog and multivariate linear regression methodologies, average predictability properties are estimated for forecasts initiated from every state on the control trajectories. For basinwide measures of predictability, the influence of the initial state tends to last for roughly a decade in both basins, but this limit varies widely among the models, especially in the North Atlantic. Within each basin, predictability varies regionally by as much as a factor of 10 for a given model, and the locations of highest predictability are different for each model. Model-to-model variations in predictability are also seen in the behavior of prominent intrinsic basin modes. Predictability is primarily determined by the mean of forecast distributions rather than the spread about the mean. Horizontal propagation plays a large role in the evolution of these signals and is therefore a key factor in differentiating the predictability of the various models.

Description: Sudden stratospheric warmings are prominent examples of dynamical wave–mean flow interactions in the Arctic stratosphere during Northern Hemisphere winter. They are characterized by a strong temperature increase on time scales of a few days and a strongly disturbed stratospheric vortex. This work investigates a wide class of supervised learning methods with respect to their ability to classify stratospheric warmings, using temperature anomalies from the Arctic stratosphere and atmospheric forcings such as ENSO, the quasi-biennial oscillation (QBO), and the solar cycle. It is demonstrated that one representative of the supervised learning methods family, namely nonlinear neural networks, is able to reliably classify stratospheric warmings. Within this framework, one can estimate temporal onset, duration, and intensity of stratospheric warming events independently of a particular pressure level. In contrast to classification methods based on the zonal-mean zonal wind, the approach herein distinguishes major, minor, and final warmings. Instead of a binary measure, it provides continuous conditional probabilities for each warming event representing the amount of deviation from an undisturbed polar vortex. Additionally, the statistical importance of the atmospheric factors is estimated. It is shown how marginalized probability distributions can give insights into the interrelationships between external factors. This approach is applied to 40-yr and interim ECMWF (ERA-40/ERA-Interim) and NCEP–NCAR reanalysis data for the period from 1958 through 2010.

Description: To analyze the probability density distributions of surface turbulent heat fluxes, the authors apply the twoparametric modified Fisher–Tippett (MFT) distribution to the sensible and latent turbulent heat fluxes recomputed from 6-hourly NCEP–NCAR reanalysis state variables for the period from 1948 to 2008. They derived the mean climatology and seasonal cycle of the location and scale parameters of the MFT distribution. Analysis of the parameters of probability distributions identified the areas where similar surface turbulent fluxes are determined by the very different shape of probability density functions. Estimated extreme turbulent heat fluxes amount to 1500–2000 W m22 (for the 99th percentile) and can exceed 2000 W m22 for higher percentiles in the subpolar latitudes and western boundary current regions. Analysis of linear trends and interannual variability in the mean and extreme fluxes shows that the strongest trends in extreme fluxes (more than 15 W m22 decade21) in the western boundary current regions are associated with the changes in the shape of distribution. In many regions changes in extreme fluxes may be different from those for the mean fluxes at interannual and decadal time scales. The correlation between interannual variability of themean and extreme fluxes is relatively low in the tropics, the SouthernOcean, and the Kuroshio Extension region.Analysis of probability distributions in turbulent fluxes has also been used in assessing the impact of sampling errors in theVoluntaryObserving Ship (VOS)-based surface flux climatologies, allowed for the estimation of the impact of sampling in extreme fluxes. Although sampling does not have a visible systematic effect onmean fluxes, sampling uncertainties result in the underestimation of extreme flux values exceeding 100 W m22 in poorly sampled regions.

Description: The spatial distribution of some major and trace element and isotopic characteristics of backarc Plio-Quaternary basaltic to high-Mg andesitic (51% to 58% SiO2) lavas in the southern Puna (24°S to 27°S) of the Central Andean Volcanic Zone (CVZ) reflect varying continental lithospheric thickness and the thermal state of the underlying mantle wedge and subducting plate. These lavas erupted from small cones and fissures associated with faults related to a change in the regional stress system in the southern Puna at ≈ 2 to 3 Ma. Three geochemical groups are recognized: (1) a relatively high volume intraplate group (high K; La/Ta ratio 〈25) that occurs over a thin continental lithosphere above a gap in the modern seismic zone and represents the highest percentage of mantle partial melt, (2) an intermediate volume, high-K calc-alkaline group ( La/Ta ratio 〉25) that occurs over intermediate thickness lithosphere on the margins of the seismic gap and behind the main CVZ and represents an intermediate percentage of mantle partial melt, and (3) a small-volume shoshonitic group (very high K) that occurs over relatively thick continental lithosphere in the northeast Puna and Altiplano and represents a very small percentage of mantle partial melt. Mantle-generated characteristics of these lavas are partially overprinted by mixing with melts of the overlying thickened crust as shown by the presence of quartz and feldspar xenocrysts, negative Eu anomalies (Eu/Eu 〈 0.90; most 〈 0.80), and radiogenic Sr (〉 0.7055) and Pb and nonradiogenic Nd ( εNd 〈 −0.4) isotopic ratios. Mixing calculations show that the lavas generally contain more than 20% to 25% crustal melt. The eruption of the intraplate group mafic lavas, the change in regional stress orientation, and the high elevation of the southern Puna are suggested to be the result of the late Pliocene mechanical delamination of a block (or blocks) of continental lithosphere (mantle and possibly lowermost crust). The loss of this lithosphere resulted in an influx of asthenosphere that caused heating of the subducting slab and yielded intraplate basic magmas that produced extensive melting at the base of the thickened crust. Heating of the subducting slab led to formation of the seismic gap and trenchward depletion of the slab component. Backarc calc-alkaline group lavas erupted on the margins of this delaminated block, whereas shoshonitic group lavas erupted over a zone of relatively thick nondelaminated lithosphere to the north.

Description: New charts of bathymetry, acoustic character, and sediment distribution describe the Hess Rise, a large oceanic plateau in the central north Pacific. Discrete physiographic provinces on the Hess Rise are the High Plateau, shallower than 3900 m, trending N30°W; the Northeastern Flank, a smooth, gentle slope gradually increasing in depth to the northeast; the Woollard Abyssal Plain, extending farther to the northeast; the Volcanic Province with its high peaks and ridges along the southern margin of the Hess Rise; the Mendocino Fracture Zone to the south, expressed by broad, planar seafloor regions bordered by ridges and scarps; the Western Steps, formed by structural benches on the western side of the Rise; and the Emperor Deep, between the rise and the Emperor Seamounts. Five types of acoustic units have been mapped and interpreted: a transparent layer, predominantly of biosiliceous pelagic clay; a stratified layer, predominantly of nannofossil ooze; a diffuse layer of debris flows that seem to have originated mostly in the Volcanic Province; an opaque horizon commonly formed of volcaniclastic sediments that are usually found on the seafloor of the Mendocino Fracture Zone; and a hyperbolic horizon, indicating outcrops of igneous rock. The pronounced effect of bottom currents on the present-day environment of deposition in the Hess Rise is evidenced by the presence of the opaque horizon, which is interpreted as an erosion surface, and by current moating, abrupt thinning of surface layers and truncation of subbottom reflectors. The widespread erosion on the seafloor of the Mendocino Fracture Zone is attributed to the flow of Antarctic bottom water.

Description: Antarctic Intermediate Water (AAIW) is a dominant Southern Hemisphere water mass that spreads from its formation regions just north of the Antarctic Circumpolar Current (ACC) to at least 20°S in all oceans. This study uses an isopycnal climatology constructed from Argo conductivity–temperature–depth (CTD) profile data to define the current state of the AAIW salinity minimum (its core) and thence compute anomalies of AAIW core pressure, potential temperature, salinity, and potential density since the mid-1970s from ship-based CTD profiles. The results are used to calculate maps of temporal property trends at the AAIW core, where statistically significant strong circumpolar shoaling (30–50 dbar decade−1), warming (0.05°–0.15°C decade−1), and density reductions [up to −0.03 (kg m−3) decade−1] are found. These trends are strongest just north of the ACC in the southeast Pacific and Atlantic Oceans and decrease equatorward. Salinity trends are generally small, with their sign varying regionally. Bottle data are used to extend the AAIW core potential temperature anomaly analysis back to 1925 in the Atlantic and to ~1960 elsewhere. The modern warm AAIW core conditions appear largely unprecedented in the historical record: biennially and zonally binned median AAIW core potential temperatures within each ocean basin are, with the notable exception of the subtropical South Atlantic in the 1950s–70s, 0.2–1°C colder than modern values. Zonally averaged sea surface temperature anomalies around the AAIW formation latitudes in each ocean and sectoral southern annular mode indices are used to put the AAIW core property trends and variations into context.

Description: Anthropogenic emissions of greenhouse gases could lead to undesirable effects on oceans in coming centuries. Drawing on recommendations published by the German Advisory Council on Global Change, levels of unacceptable global marine change (so-called guardrails) are defined in terms of global mean temperature, sea level rise, and ocean acidification. A global-mean climate model [the Aggregated Carbon Cycle, Atmospheric Chemistry and Climate Model (ACC2)] is coupled with an economic module [taken from the Dynamic Integrated Climate–Economy Model (DICE)] to conduct a cost-effectiveness analysis to derive CO2 emission pathways that both minimize abatement costs and are compatible with these guardrails. Additionally, the “tolerable windows approach” is used to calculate a range of CO2 emissions paths that obey the guardrails as well as a restriction on mitigation rate. Prospects of meeting the global mean temperature change guardrail (2° and 0.2°C decade−1 relative to preindustrial) depend strongly on assumed values for climate sensitivity: at climate sensitivities 〉3°C the guardrail cannot be attained under any CO2 emissions reduction strategy without mitigation of non-CO2 greenhouse gases. The ocean acidification guardrail (0.2 unit pH decline relative to preindustrial) is less restrictive than the absolute temperature guardrail at climate sensitivities 〉2.5°C but becomes more constraining at lower climate sensitivities. The sea level rise and rate of rise guardrails (1 m and 5 cm decade−1) are substantially less stringent for ice sheet sensitivities derived in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report, but they may already be committed to violation if ice sheet sensitivities consistent with semiempirical sea level rise projections are assumed.

Description: Intraspecific variation in characters such as arm sucker and gill lamellae counts in octopodids is yet to be thoroughly investigated, potentially hampering our ability to recognize species. In this study, data from 13 specimens of Muusoctopus hydrothermalis collected at four hydrothermal vents on the East Pacific Rise between 8°38′N and 12°48′N are considered. Although the northern and southern octopuses differ minimally in size, mean sucker count by arm in the northern group is 11.7 to 22.8% higher than it is in the southern group; in addition these octopuses typically have an additional gill lamella and bulkier funnel organs. The arms of each individual carry a different number of suckers. The difference is significant on nonadjacent arms, a pattern that merits examination in a broader taxonomic context. Why these differences exist among conspecifics remains unknown, the incidence of parasitic copepods is not different between the groups and the between-group variation in arm suckers seen here compares well with a previous report of variation among 18 specimens from the type locality. Increases in meristic characters (counts) in fish are attributed to lower temperatures during embryonic development following Jordan's rule. Northern and southern vents offer the octopuses a wide temperature range, but vent fluid chemistry differs. Northern vent fluids may be more toxic; if so, developing octopus embryos may survive only minimal vent fluid exposure and therefore develop at low temperatures. At the less toxic southern vents, eggs may survive greater exposure to vent fluids and thus develop at higher temperatures.

Description: We present a conceptual model of fluid circulation in a ridge flank hydrothermal system, the Mariana Mounds. The model is based on chemical data from pore waters extracted from piston cores and from push cores collected by deep‐sea research vessel Alvin in small, meter‐sized mounds situated on a local topographic high. These mounds are located within a region of heat flow exceeding that calculated from a conductive model and are zones of strong pore water upflow. We have interpreted the chemical data with time‐dependent transport‐reaction models to estimate pore water velocities. In the mounds themselves pore water velocities reach several meters per year to kilometers per year. Within about 100 m from these zones of focused upflow velocities decrease to several centimeters per year up to tens of centimeters per year. A larger area of low heat flow surrounds these heat flow and topographic highs, with upwelling pore water velocities less than 2 cm/yr. In some nearby cores, downwelling of bottom seawater is evident but at speeds less than 2 cm/yr. Downwelling through the sediments appears to be a minor source of seawater recharge to the basaltic basement. We conclude that the principal source of seawater recharge to basement is where basement outcrops exist, most likely a scarp about 2–4 km to the east and southeast of the study area.

Description: Historical hydrographic data (1940s–2010) show a distinct cross-slope difference of the lower halocline water (LHW) over the Laptev Sea continental margins. Over the slope, the LHW is on average warmer and saltier by 0.2°C and 0.5 psu, respectively, relative to the off-slope LHW. The LHW temperature time series constructed from the on-slope historical records are related to the temperature of the Atlantic Water (AW) boundary current transporting warm water from the North Atlantic Ocean. In contrast, the on-slope LHW salinity is linked to the sea ice and wind forcing over the potential upstream source region in the Barents and northern Kara Seas, as also indicated by hydrodynamic model results. Over the Laptev Sea continental margin, saltier LHW favors weaker salinity stratification that, in turn, contributes to enhanced vertical mixing with underlying AW.

Description: The equatorial deep jets (EDJ) are a striking feature of the equatorial ocean circulation. In the Atlantic Ocean, the EDJ are associated with a vertical scale of between 300 and 700 m, a time scale of roughly 4.5 years and upward energy propagation to the surface. It has been found that the meridional width of the EDJ is roughly 1.5 times larger than expected based on their vertical scale. Here we use a shallow water model for a high order baroclinic vertical normal mode to argue that mixing of momentum along isopycnals can explain the enhanced width. A lateral eddy viscosity of 300 m2 s−1 10 is found to be sufficient to account for the width implied by observations.

Description: The Cycladic blueschist belt, Greece, is mostly submerged below sea level and regional correlations are difficult to establish. Marbles are widespread within the belt and locally used as marker horizons to subdivide monotonous schist sequences. However, owing to the lack of distinctive petrographic characteristics, the marbles have not been used for island-to-island correlations. This study aims to investigate the potential of Sr-, C- and O-isotope compositions of marbles as a tool for unravelling the litho- and/or tectonostratigraphic relationships across the Cycladic islands, and as a proxy for the time of sediment formation. For this purpose, we have studied metamorphic carbonate rocks from the islands of Tinos, Andros, Syros, Sifnos and Naxos. Identical 87Sr/86Sr values for certain marble horizons occurring on Tinos, Andros and Sifnos are interpreted to document coeval regional carbonate precipitation. The 87Sr/86Sr values of the apparently least altered samples intersect the seawater curve multiple times within the most likely time interval of original carbonate precipitation (〈 240 Ma; as indicated by previously published ion probe U–Pb zircon data) and thus an unequivocal age assignment is not possible. Very broad temporal correlations are possible, but more subtle distinctions are not feasible. On Andros, the overlapping Sr-isotope values of marbles representing the lowest and highest parts of the metamorphic succession are in accordance with a model suggesting isoclinal folding or thrusting of a single horizon, or very fast sedimentation. In contrast, distinct 87Sr/86Sr values for samples from Tinos, representing different levels of the metamorphic succession, suggest that these rocks represent a temporal succession and not the tectonic repetition of a single horizon. Based on Sr-,O- and C-isotope characteristics alone the time equivalence ofmarbles occurring on different islands could not be documented unambiguously. However, by using various combinations of these parameters, some occurrences can be discriminated from the overall sample population. The new data further accentuate the general potential of coupled Sr-, C- and O-isotope characteristics for identification of archaeological provenance and complement existing datasets for Aegean marbles.

Description: The suggestion is advanced that the remarkably low static stability of Antarctic surface waters may arise from a feedback loop involving global deep-water temperatures. If deep-water temperatures are too warm, this promotes Antarctic convection, thereby strengthening the inflow of Antarctic Bottom Water into the ocean interior and cooling the deep ocean. If deep waters are too cold, this promotes Antarctic stratification allowing the deep ocean to warm because of the input of North Atlantic Deep Water. A steady-state deep-water temperature is achieved such that the Antarctic surface can barely undergo convection. A two-box model is used to illustrate this feedback loop in its simplest expression and to develop basic concepts, such as the bounds on the operation of this loop. The model illustrates the possible dominating influence of Antarctic upwelling rate and Antarctic freshwater balance on global deep-water temperatures.

Description: The importance of decadal climate variability (DCV) research is being increasingly recognized, including by the World Climate Research Program (WCRP) and the Intergovernmental Panel on Climate Change (IPCC). An improved understanding of DCV is very important because stakeholders and policymakers want to know the likely climate trajectory for the coming decades for applications to water resources, agriculture, energy, and infrastructure development. Responding to this demand, many climate modeling groups in the United States, Europe, Japan, and elsewhere are gearing up to assess the potential for decadal climate predictions. The magnitudes of regional DCV often exceed those associated with the trends resulting from anthropogenic changes. Therefore, differentiating between the two is also very important for planning, implementation, and national and international treaties.

Description: Simple idealized layered models and primitive equation models show that the meridional gradient of the zonally averaged pressure has no direct relation with the meridional flow. This demonstrates a contradiction in an often-used parameterization in zonally averaged models. The failure of this parameterization reflects the inconsistency between the model of Stommel and Arons and the box model of Stommel, as previously pointed out by Straub. A new closure is proposed. The ocean is divided in two dynamically different regimes: a narrow western boundary layer and an interior ocean; zonally averaged quantities over these regions are considered. In the averaged equations three unknowns appear: the interior zonal pressure difference Delta p(i), the zonal pressure difference Delta p(b) of the boundary layer, and the zonal velocity us at the interface between the two regions. Here Delta p(i) is parameterized using a frictionless vorticity balance, Delta p(b), by the difference of the mean pressure in the interior and western boundary, and u(delta) by the mean zonal velocity of the western boundary layer. Zonally resolved models, a layer model, and a primitive equation model validate the new parameterization by comparing with the respective zonally averaged counterparts. It turns out that the zonally averaged models reproduce well the buoyancy distribution and the meridional flow in the zonally resolved model versions with respect to the mean and time changes.

Description: Continuous estimates of the oceanic meridional heat transport in the Atlantic are derived from the Rapid Climate Change–Meridional Overturning Circulation (MOC) and Heatflux Array (RAPID–MOCHA) observing system deployed along 26.5°N, for the period from April 2004 to October 2007. The basinwide meridional heat transport (MHT) is derived by combining temperature transports (relative to a common reference) from 1) the Gulf Stream in the Straits of Florida; 2) the western boundary region offshore of Abaco, Bahamas; 3) the Ekman layer [derived from Quick Scatterometer (QuikSCAT) wind stresses]; and 4) the interior ocean monitored by “endpoint” dynamic height moorings. The interior eddy heat transport arising from spatial covariance of the velocity and temperature fields is estimated independently from repeat hydrographic and expendable bathythermograph (XBT) sections and can also be approximated by the array. The results for the 3.5 yr of data thus far available show a mean MHT of 1.33 ± 0.40 PW for 10-day-averaged estimates, on which time scale a basinwide mass balance can be reasonably assumed. The associated MOC strength and variability is 18.5 ± 4.9 Sv (1 Sv ≡ 106 m3 s−1). The continuous heat transport estimates range from a minimum of 0.2 to a maximum of 2.5 PW, with approximately half of the variance caused by Ekman transport changes and half caused by changes in the geostrophic circulation. The data suggest a seasonal cycle of the MHT with a maximum in summer (July–September) and minimum in late winter (March–April), with an annual range of 0.6 PW. A breakdown of the MHT into “overturning” and “gyre” components shows that the overturning component carries 88% of the total heat transport. The overall uncertainty of the annual mean MHT for the 3.5-yr record is 0.14 PW or about 10% of the mean value.

Description: The water mass structure of the Arctic Ocean is remarkable, for its intermediate (depth range ~150–900 m) layer is filled with warm (temperature 〉0°C) and salty water of Atlantic origin (usually called the Atlantic Water, AW). This water is carried into and through the Arctic Ocean by the pan-Arctic boundary current, which moves cyclonically along the basins’ margins (Fig. 1). This system provides the largest input of water, heat, and salt into the Arctic Ocean; the total quantity of heat is substantial, enough to melt the Arctic sea ice cover several times over. By utilizing an extensive archive of recently collected observational data, this study provides a cohesive picture of recent large-scale changes in the AW layer of the Arctic Ocean. These recent observations show the warm pulse of AW that entered the Arctic Ocean in the early 1990s finally reached the Canada Basin during the 2000s. The second warm pulse that entered the Arctic Ocean in the mid-2000s has moved through the Eurasian Basin and is en route downstream. One of the most intriguing results of these observations is the realization of the possibility of uptake of anomalous AW heat by overlying layers, with possible implications for an already-reduced Arctic ice cover.

Description: The midwater scorpionfish Ectreposebastes imus (Scorpaeniformes: Setarchidae) is distributed in tropical and subtropical waters of the worldwide oceans, at depths of 150–800 m. It has previously been recorded from the Gulf of Guinea in the eastern Atlantic. The present work extends the northern limit for the distribution of E. imus in the Atlantic Ocean to the area of the Canary Islands.

Description: Morphologic analyses of a large collection of coleoid cephalopods from the Lebanese Upper Cretaceous yielded a much higher diversity than previously assumed and revealed numerous extraordinarily well-preserved, soft-part characters. An analysis of the Prototeuthidina, a gladius-bearing group with a slender torpedo-shaped body, revealed two species: Dorateuthis syriaca and Boreopeltis smithi n. sp. Previously unknown soft-part characters, such as the digestive tract, the gills, and the cephalic cartilage considerably improved our knowledge of D. syriaca. Since none of the investigated specimens show more than eight arms, similarities with modern squids are regarded as superficial. Boreopeltis smithi n. sp. is erected on the basis of its comparatively wide Paraplesioteuthis- like gladius. The latter species represents the first unambiguous record of this genus in Upper Cretaceous deposits. Phylogenetic analyses indicate that the prototeuthidid clade consists of two lineages. The plesioteuthidid lineage originates from early Jurassic Paraplesioteuthis and leads to Plesioteuthis and Dorateuthis. The other lineage is morphologically more conservative and leads to Boreopeltis.