Quantification of ocean heat uptake from changes in atmospheric O2 and CO2 composition

The ocean is the main source of thermal inertia in the climate system. Ocean heat uptake during recent decades has been quantified using ocean temperature measurements. However, these estimates all use the same imperfect ocean dataset and share additional uncertainty due to sparse coverage, especially before 2007. Here, we provide an independent estimate by using measurements of atmospheric oxygen (O2) and carbon dioxide (CO2) – levels of which increase as the ocean warms and releases gases – as a whole ocean thermometer. We show that the ocean gained 1.29 ± 0.79 × 1022 Joules of heat per year between 1991 and 2016, equivalent to a planetary energy imbalance of 0.80 ± 0.49 W watts per square metre of Earth’s surface. We also find that the ocean-warming effect that led to the outgassing of O2 and CO2 can be isolated from the direct effects of anthropogenic emissions and CO2 sinks. Our result – which relies on high-precision O2 atmospheric measurements dating back to 1991 – leverages an integrative Earth system approach and provides much needed independent confirmation of heat uptake estimated from ocean data

Processes and patterns of oceanic nutrient limitation

Microbial activity is a fundamental component of oceanic nutrient cycles. Photosynthetic microbes, collectively termed phytoplankton, are responsible for the vast majority of primary production in marine waters. The availability of nutrients in the upper ocean frequently limits the activity and abundance of these organisms. Experimental data have revealed two broad regimes of phytoplankton nutrient limitation in the modern upper ocean. Nitrogen availability tends to limit productivity throughout much of the surface low-latitude ocean, where the supply of nutrients from the subsurface is relatively slow. In contrast, iron often limits productivity where subsurface nutrient supply is enhanced, including within the main oceanic upwelling regions of the Southern Ocean and the eastern equatorial Pacific. Phosphorus, vitamins and micronutrients other than iron may also (co-)limit marine phytoplankton. The spatial patterns and importance of co-limitation, however, remain unclear. Variability in the stoichiometries of nutrient supply and biological demand are key determinants of oceanic nutrient limitation. Deciphering the mechanisms that underpin this variability, and the consequences for marine microbes, will be a challenge. But such knowledge will be crucial for accurately predicting the consequences of ongoing anthropogenic perturbations to oceanic nutrient biogeochemistry. © 2013 Macmillan Publishers Limited. All rights reserved

Global-scale variations of the ratios of carbon to phosphorus in exported marine organic matter

The ratio of carbon (C) to phosphorus (P) in marine phytoplankton is thought to be constant throughout the worlds'oceans. Known as the Redfield ratio, this relationship describes the links between carbon and phosphorus cycling and marine ecosystems. However, variations in the stoichiometry of phytoplankton have recently been identified, in particular strong latitudinal variability. Here we assess the impact of this variability in the C:P ratio of biomass on the C:P ratio of organic matter that is exported to the deep ocean using a biogeochemical inverse-model based on a data-constrained ocean circulation model and a global database of dissolved inorganic carbon and phosphate measurements. We identify global patterns of variability in the C:P ratios of exported organic matter, with higher values in the nutrient-depleted subtropical gyres, where organic matter export is relatively low, and lower ratios in nutrient-rich upwelling zones and high-latitude regions, where organic matter export is high. This suggests that total carbon export is relatively constant throughout the oceans, in agreement with recent estimates of carbon fluxes. We conclude that the latitudinal patterns of C:P in exported organic matter are consistent with the large-scale stoichiometric variations in phytoplankton C:P. We suggest that a future expansion of nutrient-depleted waters could result in a shift to more efficient C export that compensates for the expected decline in productivity

The neutron and its role in cosmology and particle physics

Experiments with cold and ultracold neutrons have reached a level of precision such that problems far beyond the scale of the present Standard Model of particle physics become accessible to experimental investigation. Due to the close links between particle physics and cosmology, these studies also permit a deep look into the very first instances of our universe. First addressed in this article, both in theory and experiment, is the problem of baryogenesis ... The question how baryogenesis could have happened is open to experimental tests, and it turns out that this problem can be curbed by the very stringent limits on an electric dipole moment of the neutron, a quantity that also has deep implications for particle physics. Then we discuss the recent spectacular observation of neutron quantization in the earth's gravitational field and of resonance transitions between such gravitational energy states. These measurements, together with new evaluations of neutron scattering data, set new constraints on deviations from Newton's gravitational law at the picometer scale. Such deviations are predicted in modern theories with extra-dimensions that propose unification of the Planck scale with the scale of the Standard Model ... Another main topic is the weak-interaction parameters in various fields of physics and astrophysics that must all be derived from measured neutron decay data. Up to now, about 10 different neutron decay observables have been measured, much more than needed in the electroweak Standard Model. This allows various precise tests for new physics beyond the Standard Model, competing with or surpassing similar tests at high-energy. The review ends with a discussion of neutron and nuclear data required in the synthesis of the elements during the "first three minutes" and later on in stellar nucleosynthesis.Comment: 91 pages, 30 figures, accepted by Reviews of Modern Physic

Oceans and Coastal Ecosystems and Their Services

Ocean and coastal ecosystems support life on Earth and many aspects of human well-being. Covering two-thirds of the planet, the ocean hosts vast biodiversity and modulates the global climate system by regulating cycles of heat, water and elements, including carbon. Marine systems are central to many cultures, and they also provide food, minerals, energy and employment to people. Since previous assessments1 , new laboratory studies, field observations and process studies, a wider range of model simulations, Indigenous knowledge, and local knowledge have provided increasing evidence on the impacts of climate change on ocean and coastal systems, how human communities are experiencing these impacts, and the potential solutions for ecological and human adaptation.Peer reviewe

Oceanic nitrogen cycling and N2 O flux perturbations in the Anthropocene

There is currently no consensus on how humans are affecting the marine nitrogen (N) cycle, which limits marine biological production and CO2 uptake. Anthropogenic changes in ocean warming, deoxygenation, and atmospheric N deposition can all individually affect the marine N cycle and the oceanic production of the greenhouse gas nitrous oxide (N2O). However, the combined effect of these perturbations on marine N cycling, ocean productivity, and marine N2O production is poorly understood. Here we use an Earth system model of intermediate complexity to investigate the combined effects of estimated 21st century CO2 atmospheric forcing and atmospheric N deposition. Our simulations suggest that anthropogenic perturbations cause only a small imbalance to the N cycle relative to preindustrial conditions (∼+5 Tg N y−1 in 2100). More N loss from water column denitrification in expanded oxygen minimum zones (OMZs) is counteracted by less benthic denitrification, due to the stratification-induced reduction in organic matter export. The larger atmospheric N load is offset by reduced N inputs by marine N2 fixation. Our model predicts a decline in oceanic N2O emissions by 2100. This is induced by the decrease in organic matter export and associated N2O production and by the anthropogenically driven changes in ocean circulation and atmospheric N2O concentrations. After comprehensively accounting for a series of complex physical-biogeochemical interactions, this study suggests that N flux imbalances are limited by biogeochemical feedbacks that help stabilize the marine N inventory against anthropogenic changes. These findings support the hypothesis that strong negative feedbacks regulate the marine N inventory on centennial time scales