Adjustment of the natural ocean carbon cycle to negative emission rates

Carbon dioxide removal (CDR) is the only geoengineering technique that allows negative emissions and the reduction of anthropogenic carbon in the atmosphere. Since the time scales of the global carbon cycle are largely driven by the exchanges with the natural oceanic stocks, the implementation of CDR actions is anticipated to create outgassing from the ocean that may reduce their efficiency. The adjustment of the natural carbon cycle to CDR was studied with a numerical Earth System Model, focusing on the oceanic component and considering two idealized families of CDR policies, one based on a target atmospheric concentration and one based on planned negative emissions. Results show that both actions are anticipated to release the anthropogenic carbon stored in the surface ocean, effectively increasing the required removal effort. The additional negative emissions are expected to be lower when the CDR policy is driven by planned removal rates without prescribing a target atmospheric CO2 concentration

Issues in stochastic ocean modeling

The general theory of stochastic differential equations is presented in this chapter, including the theoretical background on how measured statistics from time series can be used to develop a stochastic parameterization. The general rules of stochastic calculus, including the important and often overlooked differences between Ito and Stratonovich calculus, are mentioned, and references are provided in which more detail may be found. We discuss how Stratonovich calculus is usually appropriate for fluid systems, whereas Ito calculus is often appropriate for data assimilation. We also discuss some common numerical pitfalls awaiting the unwary modeler, and warn against unsophisticated random number generators. Finally, we offer a selection of examples showing the importance of the variability of unresolved scales in an ocean model and, by citation, a variety of methods that have been employed

Baroclinic stationary waves in aquaplanet models

An aquaplanet model is used to study the nature of the highly persistent low-frequency waves that have been observed in models forced by zonally symmetric boundary conditions. Using the Hayashi spectral analysis of the extratropical waves, the authors find that a quasi-stationary wave 5 belongs to a wave packet obeying a well-defined dispersion relation with eastward group velocity. The components of the dispersion relation with k ≥ 5 baroclinically convert eddy available potential energy into eddy kinetic energy, whereas those with k < 5 are baroclinically neutral. In agreement with Green’s model of baroclinic instability, wave 5 is weakly unstable, and the inverse energy cascade, which had been previously proposed as a main forcing for this type of wave, only acts as a positive feedback on its predominantly baroclinic energetics. The quasi-stationary wave is reinforced by a phase lock to an analogous pattern in the tropical convection, which provides further amplification to the wave. It is also found that the Pedlosky bounds on the phase speed of unstable waves provide guidance in explaining the latitudinal structure of the energy conversion, which is shown to be more enhanced where the zonal westerly surface wind is weaker. The wave’s energy is then trapped in the waveguide created by the upper tropospheric jet stream. In agreement with Green’s theory, as the equator-to-pole SST difference is reduced, the stationary marginally stable component shifts toward higher wavenumbers, while wave 5 becomes neutral and westward propagating. Some properties of the aquaplanet quasi-stationary waves are found to be in interesting agreement with a low frequency wave observed by Salby during December–February in the Southern Hemisphere so that this perspective on low frequency variability, apart from its value in terms of basic geophysical fluid dynamics, might be of specific interest for studying the earth’s atmosphere

Preface: The SINTEX Project

The project called Decadal and Interdecadal Climate Variability: Scales Interactions Experiments (SINTEX), was conceived in 1997, stemming from a series of discussions and meetings within The EUROCLIVAR..

TROPICAL CYCLONE ACTIVITY IN A WARMER CLIMATE AS SIMULATED BY A HIGH RESOLUTION COUPLED GENERAL CIRCULATION MODEL:CHANGES IN FREQUENCY AND AIR-SEA INTERACTION

This study investigates the possible changes that the greenhouse global warming might generate in the character- istics of the tropical cyclones (TCs). The analysis has been performed using climate scenario simulations carried out with a fully coupled high–resolution global general circulation model (INGV-SXG) with a T106 atmospheric resolution. The capability of the model to reproduce a reasonably realistic TC climatology has been assessed by comparing the model results from a simulation of the XX Century with observations. The model appears to be able to simulate tropical cyclone-like vortices with many features similar to the observed TCs. The simulated TC activity exhibits realistic geographical distribution, seasonal modulation and interannual variability, suggesting that the model is able to reproduce the major basic mechanisms that link the TC occurrence with the large scale circulation. The results from the climate scenarios reveal a substantial general reduction of the TC frequency when the atmospheric CO2 concentration is doubled and quadrupled. The reduction appears particularly evident for the tropical north west Pacific (NWP) and north Atlantic (ATL). In the NWP the weaker TC activity seems to be associated with a reduced amount of convective instabilities. In the ATL region the weaker TC activity seems to be due to both the increased stability of the atmosphere and a stronger vertical wind shear. Despite the generally reduced TC activity, there is evidence of increased rainfall associated with the simulated cyclones. Using the new fully coupled CMCC model (CMCC_MED), with a T159 atmospheric resolution, we found a significant modulation of the Ocean Heat Transport (OHT) induced by the TC activity. Thus the possible changes that greenhouse induced global warming during 21st century might generate in the characteristics of the TC-induced OHT have been analyzed

A General Methodology for Beached Oil Spill Hazard Mapping

The current lack of a standardized approach to compute the coastal oil spill hazard due to maritime traffic accidental releases has hindered an accurate estimate of its global impact, which is paramount to manage and intercompare the associated risks. We propose here a hazard estimation approach that is based on ensemble simulations and the extraction of the relevant distributions. We demonstrate that both open ocean and beached oil concentration distributions fit a Weibull curve, a two-parameter fat-tail probability distribution function. The simulation experiments are carried out in three different areas of the northern Atlantic. An indicator that quantify the coastal oil spill hazard is proposed and applied to the study areas

Bidimensional Diagnostics, Variability, and Trends of Northern Hemisphere Blocking

AbstractIn this paper, Northern Hemisphere winter blocking is analyzed through the introduction of a set of new bidimensional diagnostics based on geopotential height that provide information about the occurrence, the duration, the intensity, and the wave breaking associated with the blocking. This analysis is performed with different reanalysis datasets in order to evaluate the sensitivity of the index and the diagnostics adopted. In this way, the authors are able to define a new category of blocking placed at low latitudes that is similar to midlatitude blocking in terms of the introduced diagnostics but is unable to divert or block the flow. Furthermore, over the Euro-Atlantic sector it is shown that it is possible to phenomenologically distinguish between high-latitude blocking occurring over Greenland, north of the jet stream and dominated by cyclonic wave breaking, and the traditional midlatitude blocking localized over Europe and driven by anticyclonic wave breaking. These latter events are uniformly present in a band ranging from the Azores up to Scandinavia. Interestingly, a similar distinction cannot be pointed out over the Pacific basin where the blocking activity is dominated by high-latitude blocking occurring over eastern Siberia. Finally, considering the large impact that blocking may have on the Northern Hemisphere, an analysis of the variability and the trend is carried out. This shows a significant increase of Atlantic low-latitude blocking frequency and an eastward displacement of the strongest blocking events over both the Atlantic and Pacific Oceans

Estudio de inestabilidad inicial de paneles con el elmento BST

Peer Reviewe

ENSO and its effects on the atmospheric heating processes

El Nino-Southern Oscillation (ENSO) is an important air-sea coupled phenomenon that plays a dominant role in the variability of the tropical regions. Observations, atmospheric and oceanic reanalysis datasets are used to classify ENSO and non-ENSO years to investigate the typical features of its periodicity and atmospheric circulation patterns. Among non-ENSO years, we have analyzed a group, called type-II years, with very small SST anomalies in summer that tend to weaken the correlation between ENSO and precipitation in the equatorial regions. A unique character of ENSO is studied in terms of the quasi-biennial periodicity of SST and heat content (HC) fields over the Pacific-Indian Oceans. While the SST tends to have higher biennial frequency along the Equator, the HC maximizes it into two centers in the western Pacific sector. The north-western center, located east of Mindanao, is strongly correlated with SST in the NINO3 region. The classification of El Nino and La Nina years, based on NINO3 SST and north-western Pacific HC respectively, has been used to identify and describe temperature and wind patterns over an extended-ENSO region that includes the tropical Pacific and Indian Oceans. The description of the spatial patterns within the atmospheric ENSO circulation has been extended to tropospheric moisture fields and low-level moisture divergence during November-December-January, differentiating the role of El Nino, when lame amounts of condensational heat are concentrated in the central Pacific, from La Nina that tends to mainly redistribute heat to Maritime Continents and higher latitudes. The influence of the described mechanisms on equatorial convection in the context of the variability of ENSO on longer timescales for the end of the 20th century is questioned. However, the inaccuracy of the atmospheric reanalysis products in terms of precipitation and the shorter time length of more reliable datasets hamper a final conclusion on this issue