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An introduction is presented in which the editor discusses various articles within the issue on topics including arboviral disease in horses in Australia, serious injuries to Australian cattle veterinarians and chick bioassay for viral pathogens in poultry litter.

Abstract: The North Atlantic subpolar gyre is considered to be one of the strongest marine anthropogenic CO2 sinks, a consequence of extensive deep convection occurring during winter. Observations collected in this region since 1981 have shown large changes in Dissolved Inorganic Carbon (DIC) concentrations in intermediate and deep waters, which have been attributed to both anthropogenic CO2 penetration and natural variability in the ocean carbon cycle (Wanninkhof et al., 2010). In this context, we describe new δ13CDIC observations obtained in the Irminger Basin during two OVIDE cruises (2002 and 2006) which we compare to historical data (TTO-NAS 1981) in order to estimate the oceanic 13C Suess Effect over the more than twenty years that separates these surveys. The data reveal a significant decrease in δ13CDIC, of between −0.3‰ and −0.4‰ from 1981 to 2006. The anthropogenic change, extracted by using the extended Multi Linear Regression (eMLR) approach, explains 75% of this signal for oldest water mass and 90% for youngest. The reminding signal is due to the natural processes, such as remineralization and vertical mixing. The eMLR method was also applied to DIC measurements which i) reveal strong relationships between the increase of anthropogenic CO2 and the oceanic 13C Suess Effect over the whole water column during the 25-year period and ii) support the hypothesis of change in the Cant storage rate in the Irminger Basin between 1981 and 2006. [Copyright &y& Elsevier]

3He is injected in the deep ocean at plate boundaries in relation with hydrothermal activity. Its oceanic distribution, which is at a steady-state, shows appreciable vertical and horizontal gradients. Hence, 3He conservation equations may be inverted to determine the flow field and mixing coefficients within the ocean. Here, we use this technique to investigate the deep circulation of the Red Sea, whose deep thermohaline circulation is comparable to that of a miniature world ocean. 3He data, which are a combination of the Geosecs, Meseda and Merou cruises, are inverted using a linear inverse box model. The present study allows us to draw the details of the internal circulation. The latter is characterized by (i) a descending branch in the northernmost part of the basin, which corresponds to the sinking and subsequent north–south movement of dense surface waters and of additional water entrained by the sinking plume, (ii) by an internal counterclockwise recirculating loop with a northward return flow at intermediate depth.In the literature, the rate and modes of renewal of the Red Sea deep waters are poorly constrained, with bulk residence time estimates ranging from a few decades to a few centuries. In our model, the deep water renewal rate is directly dependent on the magnitude of the 3He sources. The global 3He flux is estimated using two independent approaches. The first method is based on the calculation of the mean 3He transfer flux at the air–sea interface. The second approach relies on recent estimates of the global terrestrial 3He flux. Both methods agree within their respective uncertainties. The circulation scheme defined by the inversion is further constrained by simulating the bomb 14C distribution. Both isotopes, one steady-state tracer (3He) and one transient tracer (14C), lead to reasonable agreement. The renewal time corresponding to the sinking of newly formed deep water in the northern part of the basin is 60 years. However, the global ventilation rate, deduced from the simulation of the decay rate of a numerical tracer, is much faster (26 years). This result shows, as already pointed out by others, that deep water formation is not the only process by which the deep Red Sea is ventilated. Although this mechanism is important in our model, the basin wide deep circulation coupled with efficient vertical exchange between the deep basin and the upper layers appear to be an even more powerful mode of ventilation. [Copyright &y& Elsevier]

Abstract: We examine observations from 1990 to 2006 from four voluntary observing ships and two time-series stations in the North Atlantic, fitting a sinusoidal annual cycle and linear year-on-year trend at all locations where there are sufficient data. Results show that in the subtropical regions, sea-surface fCO2 has closely followed the increasing trend in atmospheric fCO2. In contrast, farther north, sea-surface fCO2 has increased faster than fCO2 in the atmosphere. The resulting ΔfCO2, driving air–sea flux of CO2, has therefore decreased in the North Atlantic, particularly at higher latitudes, as has the annual mean air–sea flux. Several underlying causes may have led to the observed changes in sea-surface fCO2. Low-frequency modes, such as the North Atlantic Oscillation, lead to changes in the sea-surface temperature, in sea-surface circulation and in vertical mixing, affecting sea-surface fCO2 through biogeochemical processes. A comparison with measurements covering a longer time period shows that the sea-surface fCO2 rise has accelerated since 1990 in the northern North Atlantic. [Copyright &y& Elsevier]

With climate projections questioning the future survival of stony corals and their dominance as tropical reef builders, it is critical to understand the adaptive capacity of corals to ongoing climate change. Biological mediation of the carbonate chemistry of the coral calcifying fluid is a fundamental component for assessing the response of corals to global threats. The Tara Pacific expedition (2016-2018) provided an opportunity to investigate calcification patterns in extant corals throughout the Pacific Ocean. Cores from colonies of the massive Porites and Diploastrea genera were collected from different environments to assess calcification parameters of long-lived reef-building corals. At the basin scale of the Pacific Ocean, we show that both genera systematically up-regulate their calcifying fluid pH and dissolved inorganic carbon to achieve efficient skeletal precipitation. However, while Porites corals increase the aragonite saturation state of the calcifying fluid (Ω cf ) at higher temperatures to enhance their calcification capacity, Diploastrea show a steady homeostatic Ω cf across the Pacific temperature gradient. Thus, the extent to which Diploastrea responds to ocean warming and/or acidification is unclear, and it deserves further attention whether this is beneficial or detrimental to future survival of this coral genus., (© 2023. The Author(s).)

The Tara Pacific expedition (2016-2018) sampled coral ecosystems around 32 islands in the Pacific Ocean and the ocean surface waters at 249 locations, resulting in the collection of nearly 58 000 samples. The expedition was designed to systematically study warm-water coral reefs and included the collection of corals, fish, plankton, and seawater samples for advanced biogeochemical, molecular, and imaging analysis. Here we provide a complete description of the sampling methodology, and we explain how to explore and access the different datasets generated by the expedition. Environmental context data were obtained from taxonomic registries, gazetteers, almanacs, climatologies, operational biogeochemical models, and satellite observations. The quality of the different environmental measures has been validated not only by various quality control steps, but also through a global analysis allowing the comparison with known environmental large-scale structures. Such publicly released datasets open the perspective to address a wide range of scientific questions., (© 2022. The Author(s).)

The hydrological cycle is expected to intensify in a warming climate. However, observational evidence of such changes in the Southern Ocean is difficult to obtain due to sparse measurements and a complex superposition of changes in precipitation, sea ice, and glacial meltwater. Here we disentangle these signals using a dataset of salinity and seawater oxygen isotope observations collected in the Indian sector of the Southern Ocean. Our results show that the atmospheric water cycle has intensified in this region between 1993 and 2021, increasing the salinity in subtropical surface waters by 0.06 ± 0.07 g kg -1 per decade, and decreasing the salinity in subpolar surface waters by -0.02 ± 0.01 g kg -1 per decade. The oxygen isotope data allow to discriminate the different freshwater processes showing that in the subpolar region, the freshening is largely driven by the increase in net precipitation (by a factor two) while the decrease in sea ice melt is largely balanced by the contribution of glacial meltwater at these latitudes. These changes extend the growing evidence for an acceleration of the hydrological cycle and a melting cryosphere that can be expected from global warming., (© 2023. The Author(s).)

Several studies have suggested that the carbon sink in the Southern Ocean-the ocean's strongest region for the uptake of anthropogenic CO2 -has weakened in recent decades. We demonstrated, on the basis of multidecadal analyses of surface ocean CO2 observations, that this weakening trend stopped around 2002, and by 2012, the Southern Ocean had regained its expected strength based on the growth of atmospheric CO2. All three Southern Ocean sectors have contributed to this reinvigoration of the carbon sink, yet differences in the processes between sectors exist, related to a tendency toward a zonally more asymmetric atmospheric circulation. The large decadal variations in the Southern Ocean carbon sink suggest a rather dynamic ocean carbon cycle that varies more in time than previously recognized., (Copyright © 2015, American Association for the Advancement of Science.)

The oceans are an important sink for anthropogenically produced CO(2), and on time scales longer than a century they will be the main repository for the CO(2) that humans are emitting. Our knowledge of how ocean uptake varies (regionally and temporally) and the processes that control it is currently observation-limited. Traditionally, and based on sparse observations and models at coarse resolution, ocean uptake has been thought to be relatively invariant. However, in the few places where we have enough observations to define the uptake over periods of many years or decades, it has been found to change substantially at basin scales, responding to indices of climate variability. We illustrate this for three well-studied regions: the equatorial Pacific, the Indian Ocean sector of the Southern Ocean, and the North Atlantic. A lesson to take from this is that ocean uptake is sensitive to climate (regionally, but presumably also globally). This reinforces the expectation that, as global climate changes in the future owing to human influences, ocean uptake of CO(2) will respond. To evaluate and give early warning of such carbon-climate feedbacks, it is important to track trends in both ocean and land sinks for CO(2). Recent coordinated observational programmes have shown that, by organization of an observing network, the atmosphere-ocean flux of CO(2) can, in principle, be accurately tracked at seasonal or better resolution, over at least the Northern Hemisphere oceans. This would provide a valuable constraint on both the ocean and (by difference) land vegetation sinks for atmospheric CO(2)., (© 2011 The Royal Society)

The oceans are a major sink for atmospheric carbon dioxide (CO2). Historically, observations have been too sparse to allow accurate tracking of changes in rates of CO2 uptake over ocean basins, so little is known about how these vary. Here, we show observations indicating substantial variability in the CO2 uptake by the North Atlantic on time scales of a few years. Further, we use measurements from a coordinated network of instrumented commercial ships to define the annual flux into the North Atlantic, for the year 2005, to a precision of about 10%. This approach offers the prospect of accurately monitoring the changing ocean CO2 sink for those ocean basins that are well covered by shipping routes.

Based on observed atmospheric carbon dioxide (CO2) concentration and an inverse method, we estimate that the Southern Ocean sink of CO2 has weakened between 1981 and 2004 by 0.08 petagrams of carbon per year per decade relative to the trend expected from the large increase in atmospheric CO2. We attribute this weakening to the observed increase in Southern Ocean winds resulting from human activities, which is projected to continue in the future. Consequences include a reduction of the efficiency of the Southern Ocean sink of CO2 in the short term (about 25 years) and possibly a higher level of stabilization of atmospheric CO2 on a multicentury time scale.