ALBERT

Description: We investigate the origin of the equatorial Pacific cold sea surface temperature (SST) bias and its link to wind biases, local and remote, in the Kiel Climate Model (KCM). The cold bias is common in climate models participating in the 5 th and 6 th phases of the Coupled Model Intercomparison Project. In the coupled experiments with the KCM, the interannually varying NCEP/CFSR wind stress is prescribed over four spatial domains: globally, over the equatorial Pacific (EP), the northern Pacific (NP) and southern Pacific (SP). The corresponding EP SST bias is reduced by 100%, 52%, 12% and 23%, respectively. Thus, the EP SST bias is mainly attributed to the local wind bias, with small but not negligible contributions from the extratropical regions. Erroneous ocean circulation driven by overly strong winds cause the cold SST bias, while the surface-heat flux counteracts it. Extratropical Pacific SST biases contribute to the EP cold bias via the oceanic subtropical gyres, which is further enhanced by dynamical coupling in the equatorial region. The origin of the wind biases is examined by forcing the atmospheric component of the KCM in a stand-alone mode with observed SSTs and simulated SSTs from the coupled experiments. Wind biases over the EP, NP and SP regions originate in the atmosphere model. The cold EP SST bias substantially enhances the wind biases over all three regions, while the NP and SP SST biases support local amplification of the wind bias. This study suggests that improving surface-wind stress, at and off the equator, is a key to improve mean-state equatorial Pacific SST in climate models.

Description: We characterize and decipher the resistome and the virulence factors of Shewanella algae MARS 14, a multidrug-resistant clinical strain using the whole genome sequencing (WGS) strategy. The bacteria were isolated from the bronchoalveolar lavage of a hospitalized patient in the Timone Hospital in Marseille, France who developed pneumonia after plunging into the Mediterranean Sea. Results: The genome size of S. algae MARS 14 was 5,005,710 bp with 52.8% guanine cytosine content. The resistome includes members of class C and D beta-lactamases and numerous multidrug-efflux pumps. We also found the presence of several hemolysins genes, a complete flagellum system gene cluster and genes responsible for biofilm formation. Moreover, we reported for the first time in a clinical strain of Shewanella spp. the presence of a bacteriocin (marinocin). Conclusion: The WGS analysis of this pathogen provides insight into its virulence factors and resistance to antibiotics.

Description: Sponges (Porifera) are one of the most ancient animals present on the planet. They are aquatic, filter-feeding sessile metazoans that rely on asexual and sexual reproduction. These animals have a long history on Earth and had plenty of time to develop different reproductive strategies. Here, we review different aspects of the physiology of reproduction in Porifera. This chapter is divided into six sections. In the first section, we present general features of sponge reproduction, such as factors that trigger the onset of their reproduction, as well as the periodicity of their reproductive cycles. The molecular basis of the hormonal control of gametogenesis is presented although sponges have no endocrine system. The second section deals with gametogenesis, 2including how sex and the germline are determined and maintained in this group, how oocytes and spermatozoa are formed and nourished, and how they behave once released. The third section reviews different topics about the reproductive mode. Here, we discuss the dichotomy in reproductive mode: oviparity vs. viviparity, the spatial distribution of the reproductive elements in the sponge tissue, the effect of symbiosis in reproduction (and vice-versa), and energetic trade-offs during reproduction. The fourth section describes fertilization, and we cover the factors controlling the spawning events and how the sperm are attracted and recognized by the egg. The diversity of developmental modes, the molecular control of sponge embryonic development, and the maternal-embryo relationship are discussed in the fifth section. Finally, in the sixth section, the types of asexual reproduction, factors influencing budding, gemmulation, hibernation, and gemmule development are described. Knowledge about the physiology of reproduction of sponges is still fragmentary and based on studies in very few species. Consequently, there are many generalizations that need further investigation. However, evidence-based on morphological, experimental, and molecular data demonstrates that their physiology is not very different from that of other metazoans

Description: The extent of our duties to mitigate climate change is commonly conceptualized in terms of temperature goals like the 1.5°C and the 2°C target and corresponding emissions budgets. While I do acknowledge the political advantages of any framework that is relatively easy to understand, I argue that this particular framework does not capture the true extent of our mitigation duties. Instead I argue for a more differentiated approach that is based on the well-known distinction between subsistence and luxury emissions. At the heart of this approach lies the argument that we have no budget of substantial, net-positive luxury emissions left. In a world in which dangerous climate change has begun, we must expect all further substantial, net-positive luxury emissions to cause harm. Since they lack the kind of justification needed for them to be nevertheless permissible, I conclude that we must stop emitting them with immediate effect. I also briefly discuss the difficult case of subsistence emissions and offer some first thoughts on the morality of a third category of emissions, what I call ‘transition emissions’.

Description: For decades oceanographers have understood the Atlantic meridional overturning circulation (AMOC) to be primarily driven by changes in the production of deep-water formation in the subpolar and subarctic North Atlantic. Indeed, current Intergovernmental Panel on Climate Change (IPCC) projections of an AMOC slowdown in the twenty-first century based on climate models are attributed to the inhibition of deep convection in the North Atlantic. However, observational evidence for this linkage has been elusive: there has been no clear demonstration of AMOC variability in response to changes in deep-water formation. The motivation for understanding this linkage is compelling, since the overturning circulation has been shown to sequester heat and anthropogenic carbon in the deep ocean. Furthermore, AMOC variability is expected to impact this sequestration as well as have consequences for regional and global climates through its effect on the poleward transport of warm water. Motivated by the need for a mechanistic understanding of the AMOC, an international community has assembled an observing system, Overturning in the Subpolar North Atlantic Program (OSNAP), to provide a continuous record of the transbasin fluxes of heat, mass, and freshwater, and to link that record to convective activity and water mass transformation at high latitudes. OSNAP, in conjunction with the Rapid Climate Change–Meridional Overturning Circulation and Heatflux Array (RAPID–MOCHA) at 26°N and other observational elements, will provide a comprehensive measure of the three-dimensional AMOC and an understanding of what drives its variability. The OSNAP observing system was fully deployed in the summer of 2014, and the first OSNAP data products are expected in the fall of 2017.

Description: State of the climate in 2019

Description: Glacio-eustatic cycles lead to changes in sedimentation on all types of continental margins. There is, however, a paucity of sedimentation rate data over eustatic sea-level cycles in active subduction zones. During International Ocean Discovery Program Expedition 375, coring of the upper ∼110 m of the northern Hikurangi Trough Site U1520 recovered a turbidite-dominated succession deposited during the last ∼45 kyrs (Marine Isotope Stages (MIS) 1–3). We present an age model integrating radiocarbon dates, tephrochronology, and δ18O stratigraphy, to evaluate the bed recurrence interval (RI) and sediment accumulation rate (SAR). Our analyses indicate mean bed RI varies from ∼322 yrs in MIS1, ∼49 yrs in MIS2, and ∼231 yrs in MIS3. Large (6-fold) and abrupt variations in SAR are recorded across MIS transitions, with rates of up to ∼10 m/kyr occurring during the Last Glacial Maximum (LGM), and 〈1 m/kyr during MIS1 and 3. The pronounced variability in SAR, with extremely high rates during the LGM, even for a subduction zone, are the result of changes in regional sediment supply associated with climate-driven changes in terrestrial catchment erosion, and critical thresholds of eustatic sea-level change altering the degree of sediment bypassing the continental shelf and slope via submarine canyon systems.

Description: In the equatorial Atlantic Ocean, meridional velocity variability exhibits a pronounced peak on intraseasonal timescales whereas zonal velocity dominantly varies on seasonal to interannual timescales. We focus on the intraseasonal meridional velocity variability away from the near-surface layer, its source regions and its pathways into the deep ocean. This deep intraseasonal velocity variability plays a key role in equatorial dynamics as it is an important energy source for the deep equatorial circulation. The results are based on the output of a high-resolution ocean model revealing intraseasonal energy levels along the equator at all depths that are in good agreement with shipboard and moored velocity data. Spectral analyses reveal a pronounced signal of intraseasonal Yanai waves with westward phase velocities and zonal wavelengths longer than 450 km. Different sources and characteristics of these Yanai waves are identified: near the surface between 40°W and 10°W low-baroclinic-mode Yanai waves with periods of around 30 days are exited. These waves have a strong seasonal cycle with a maximum in August. High-frequency Yanai waves (10–20-day period) are excited at the surface east of 10°W. In the region between the North Brazil Current and the Equatorial Undercurrent high-baroclinic-mode Yanai waves with periods between 30 and 40 days are generated. Yanai waves with longer periods (40-80 days) are shed from the Deep Western Boundary Current. The Yanai wave energy is carried along beams east- and downward thus explaining differences in strength, structure and periodicity of the meridional intraseasonal variability in the equatorial Atlantic Ocean.

Description: Marine heatwaves along the coast ofWestern Australia, referred to as Ningaloo Niño, have had dramatic impacts on the ecosystem in the recent decade. A number of local and remote forcing mechanisms have been put forward, however little is known about the depth structure of such temperature extremes. Utilizing an eddy-active global Ocean General Circulation Model, Ningaloo Niño and the corresponding cold Ningaloo Niña events are investigated between 1958-2016, with focus on their depth structure. The relative roles of buoyancy and wind forcing are inferred from sensitivity experiments. Composites reveal a strong symmetry between cold and warm events in their vertical structure and associated large-scale spatial patterns. Temperature anomalies are largest at the surface, where buoyancy forcing is dominant and extend down to 300m depth (or deeper), with wind forcing being the main driver. Large-scale subsurface anomalies arise from a vertical modulation of the thermocline, extending from the western Pacific into the tropical eastern Indian Ocean. The strongest Ningaloo Niños in 2000 and 2011 are unprecedented compound events, where long-lasting high temperatures are accompanied by extreme freshening, which emerges in association with La Niñas, more common and persistent during the negative phase of the Interdecadal Pacific Oscillation. It is shown that Ningaloo Niños during La Nina phases have a distinctively deeper reach and are associated with a strengthening of the Leeuwin Current, while events during El Niño are limited to the surface layer temperatures, likely driven by local atmosphere-ocean feedbacks, without a clear imprint on salinity and velocity.