Description: We present a new surface-atmospheric dataset for driving ocean–sea-ice models based on Japanese 55-year atmospheric reanalysis (JRA-55), referred to here as JRA55-do. The JRA55-do dataset aims to replace the CORE interannual forcing version 2 (hereafter called the CORE dataset), which is currently used in the framework of the Coordinated Ocean-ice Reference Experiments (COREs) and the Ocean Model Intercomparison Project (OMIP). A major improvement in JRA55-do is the refined horizontal grid spacing (∼ 55 km) and temporal interval (3 hr). The data production method for JRA55-do essentially follows that of the CORE dataset, whereby the surface fields from an atmospheric reanalysis are adjusted relative to reference datasets. To improve the adjustment method, we use high-quality products derived from satellites and from several other atmospheric reanalysis projects, as well as feedback on the CORE dataset from the ocean modelling community. Notably, the surface air temperature and specific humidity are adjusted using multi-reanalysis ensemble means. In JRA55-do, the downwelling radiative fluxes and precipitation, which are affected by an ambiguous cloud parameterisation employed in the atmospheric model used for the reanalysis, are based on the reanalysis products. This approach represents a notable change from the CORE dataset, which imported independent observational products. Consequently, the JRA55-do dataset is more self-contained than the CORE dataset, and thus can be continually updated in near real-time. The JRA55-do dataset extends from 1958 to the present, with updates expected at least annually. This paper details the adjustments to the original JRA-55 fields, the scientific rationale for these adjustments, and the evaluation of JRA55-do. The adjustments successfully corrected the biases in the original JRA-55 fields. The globally averaged features are similar between the JRA55-do and CORE datasets, implying that JRA55-do can suitably replace the CORE dataset for use in driving global ocean–sea-ice models.

Description: The term ldquomud volcano systemrdquo is coined to describe the set of structures associated with a constructional edifice (mud volcano) and feeder complex that connects the volcano to its source stratigraphic unit. Three-dimensional (3-D) seismic data from the South Caspian Basin are used to investigate the structural elements and evolution of these systems. Mud volcano systems initiate via early, kilometer-scale, biconic edifices termed ldquopioneerrdquo cones. These are fed by fluidization pipes tens of meters in width. Subsequent kilometer-scale mud volcanoes grew via persistent extrusion, fed by numerous additional fluidization pipes injected in the country rock. This subvolcanic intrusion complex creates a densely intruded, cylindrical zone, similar in cross section to gryphon swarms observed at an outcrop onshore. Wall rock erosion and compaction of the intruded zone leads to the collapse of a downward-tapering cone enveloping the cylindrical zone, capped by ring faults that define a kilometer-scale caldera that downthrows the overlying mud volcano. Mud volcanoes get buried during basin subsidence and can look like intrusive laccoliths at first glance on seismic data. Reactivation of mud flow through a conduit system generates a stack of superimposed mud volcanoes through time. Large volcanoes continue to dewater during burial and may locally remobilize. This model of mud volcano evolution has similarities with igneous and salt tectonic systems. To reduce drilling and geologic uncertainty, mud volcano system extent and impacts on a reservoir can be assessed on 3-D seismic data.

Description: Interest in stratospheric aerosol and its role in climate have increased over the last decade due to the observed increase in stratospheric aerosol since 2000 and the potential for changes in the sulfur cycle induced by climate change. This review provides an overview about the advances in stratospheric aerosol research since the last comprehensive assessment of stratospheric aerosol was published in 2006. A crucial development since 2006 is the substantial improvement in the agreement between in situ and space-based inferences of stratospheric aerosol properties during volcanically quiescent periods. Furthermore, new measurement systems and techniques, both in situ and space based, have been developed for measuring physical aerosol properties with greater accuracy and for characterizing aerosol composition. However, these changes induce challenges to constructing a long-term stratospheric aerosol climatology. Currently, changes in stratospheric aerosol levels less than 20% cannot be confidently quantified. The volcanic signals tend to mask any nonvolcanically driven change, making them difficult to understand. While the role of carbonyl sulfide as a substantial and relatively constant source of stratospheric sulfur has been confirmed by new observations and model simulations, large uncertainties remain with respect to the contribution from anthropogenic sulfur dioxide emissions. New evidence has been provided that stratospheric aerosol can also contain small amounts of nonsulfate matter such as black carbon and organics. Chemistry-climate models have substantially increased in quantity and sophistication. In many models the implementation of stratospheric aerosol processes is coupled to radiation and/or stratospheric chemistry modules to account for relevant feedback processes

Description: Geological and geophysical data indicate that the Precambrian basement of the North China Craton (NCC) formed by amalgamation of a number of micro-continental blocks. The number of blocks, when they existed and how they came together are controversial, and in particular the following issues are disputed: (1) the timing of collisional event(s) leading to the amalgamation of the Eastern and Western blocks along the Trans-North China Orogen (TNCO); (2) the polarity of the subduction between the Eastern and Western blocks; (3) the validity of an old continental block (Fuping Block) that collided with the Eastern Block at ∼2.1 Ga; (4) the tectonic setting of the northern margin of the NCC in the Paleoproterozoic; (5) the tectonic nature of high-pressure (HP) and ultrahigh temperature (UHT) granulite-facies events in the Khondalite Belt of the Western Block; and (6) the tectonic setting of the Paleoproterozoic Jiao-Liao-Ji Belt in the Eastern Block. Analysis and integration of available stratigraphic, structural, geochemical, metamorphic and geochronologic data enable the development of an internally consistent and coherent model for assembly and stabilization of the various Archean blocks of the NCC in the Paleoproterozoic. All metamorphic ages obtained for the TNCO are around 1.85 Ga, which establishes that the final amalgamation of the Western and Eastern blocks of the craton occurred at ∼1.85 Ga. The TNCO is characterized by a fan-shaped pattern of structural features, with the top-to-the-NW and top-to-the-SE thrusting in the northwest and southeast, respectively. This pattern does not constrain subduction polarity for the collisional assembly of the Eastern and Western blocks. Structures in lithospheric mantle and asthenosphere in the TNCO have been significantly modified/replaced in the Mesozoic and Cenozoic, and hence the present-day orientation of these structures, even if they relate to Paleoproterozoic assembly of the craton cannot be used to infer associated subduction polarity. There are no unique structural data or available metamorphic data to supporting the existence of an old continental block that intervened between the Eastern and Western Blocks, which collided with the Eastern Block at ∼2.1 Ga. Available data are also inconsistent with the existence of the Paleoproterozoic Inner Mongolia-North Hebei Orogen along the northern margin of the NCC that formed through accretion of an exotic arc at ∼2.3 Ga and incorporated into the Paleoproterozoic Columbia (Nuna) Supercontinent at 1.92–1.85 Ga. We interpret the north Hebei portion of this inferred orogen as part of the TNCO, and the Inner Mongolian portion as an independent continental block (Yinshan Block). This block is separated from the Ordos Block by the Paleoproterozoic Khondalite Belt. The high-/medium-pressure granulite facies metamorphic event in the Khondalite Belt is considered to have resulted from collision between the Yinshan and Ordos blocks to form the Western Block at ∼1.95 Ga, whereas the ∼1.92 Ga UHT metamorphism within the belt was related to the underplating or intrusion of mantle-derived magmas during the post-collisional extension. The Jiao-Liao-Ji Belt in the Eastern Block likely formed through Paleoproterozoic rifting to form the Longgang and Langrim blocks, and subsequent basin closure and collision in the period 2.2–1.9 Ga.

Description: A structural model encompassing the southern North Sea basin west of the Central Graben has been developed. This model consists of a rift system affecting the post-salt section around the basin margin and a large area of detached compressional buckle folds within the basin. This pattern is initially a response to gravity sliding of the post-salt section on the salt within the basin during the late Triassic to late Jurassic. A close relationship between the location and trend of the peripheral graben system and basement structures in the pre-salt is noted. Pre-Jurassic extension across the peripheral graben systems was balanced by the sum of fault heaves at the pre-salt (Rotliegend) level and shortening across salt-cored buckle folds in the post-salt section. Salt pillows and swells passively infilled the cores of these gravity-induced buckle folds. Cretaceous and Tertiary inversion involved basin tilt and renewed movement on basin-bounding basement faults; notably, reverse movements did not propagate from basement structures up into the peripheral graben systems. The post-salt sedimentary section experienced gravity spreading in response to inversion-related uplift, resulting in syn-inversion extensional faulting in the Sole Pit High, where the Mesozoic section was thickest. This extension, combined with a loss of fault heave in the pre-salt section, was balanced by amplification of salt-cored buckle folds in the centre of the basin. In the context of the model described here, salt pillows represent passive infill of thin-skinned, compressional buckle folds which later amplified during thick-skinned basement shortening. Crestal collapse of such folds occurs via normal faulting, accompanied by reactive diapirism. Such reactive diapirs establish conduits through which salt may leak, leading to pillow deflation and ultimately conduit preservation as a salt wall (flanked by rim synclines in areas where the buckle folds were emergent). The salt structures described here are related to cover folds and faults, which in turn reflect episodes of basin extension, tilting and inversion. Hence individual salt structures can be said to be only remotely connected with regional, intraplate stresses.

Description: The Atlantic Ocean overturning circulation is important to the climate system because it carries heat and carbon northward, and from the surface to the deep ocean. The high salinity of the subpolar North Atlantic is a prerequisite for overturning circulation, and strong freshening could herald a slowdown. We show that the eastern subpolar North Atlantic underwent extreme freshening during 2012 to 2016, with a magnitude never seen before in 120 years of measurements. The cause was unusual winter wind patterns driving major changes in ocean circulation, including slowing of the North Atlantic Current and diversion of Arctic freshwater from the western boundary into the eastern basins. We find that wind-driven routing of Arctic-origin freshwater intimately links conditions on the North West Atlantic shelf and slope region with the eastern subpolar basins. This reveals the importance of atmospheric forcing of intra-basin circulation in determining the salinity of the subpolar North Atlantic.

Description: This chapter aims at introducing the reader to general concepts about the main forcings of the Mediterranean Sea, in terms of exchanges through the Strait of Gibraltar, and air-sea exchanges of heat, freshwater, and momentum. These forcings are also responsible for the peculiar characteristics of Mediterranean water masses. Therefore, the chapter continues with giving a general explanation on water mass analysis, and then it describes the properties and vertical and horizontal distributions of the main Mediterranean water masses. To conclude, the reader is introduced to the use of other (biogeochemical, and chemical) tracers of water masses, with a focus on the Mediterranean Sea.

Description: The abundant occurrence of calcium carbonate minerals in marine sediments and their high fluorine content suggests that fluorine is a good candidate for reconstructing paleoceanographic parameters. However, the potential of fluorine as a paleoproxy had hardly been explored, and fundamental insights into the behaviour of fluorine in biogenic carbonates and marine sediments is required. A first-principles modelling approach is used here to analyse the incorporation mechanisms of fluorine into crystalline calcium carbonates. We compute F incorporation into the CaCO3 lattice via a number of mechanisms, but concentrate on comparison of the energetics of the two easiest substitution mechanisms: replacing one oxygen atom within the carbonate group to form a (CO2F)- group as against a substitution involving replacement of the CO3 group by two fluorine ions to form a CaF2 defect. These incorporation mechanisms are fundamentally different from that of iodine into calcium carbonates, where a carbon atom is replaced. Our simulations suggest that the substitution of by is the most favoured and that fluorine is preferentially incorporated into the three naturally-occurring polymorphs of calcium carbonate in the order vaterite aragonite calcite. These results explain the previously-reported preponderance of fluorine in aragonite corals, and lend support to the use of F/Ca as a proxy for ocean pCO2.