Multiscale statistical analysis of thermal and non-thermal components of seawater p CO 2 in the Western English Channel: scaling, time-reversibility, and dependence

As two most important metrics for ocean acidification (OA), both pH and calcium carbonate mineral saturation states (Ω) respond sensitively to anthropogenic carbon dioxide (CO2). However, contrary to intuition, they are often out of phase in the global surface ocean, both spatially and seasonally. For example, during warm seasons, Ω is lowest at high‐latitude seas where there are very high pH values, challenging our understanding that high‐latitude seas are a bellwether for global OA. To explain this phenomenon, we separate spatial and seasonal variations of both pH and Ω into thermal components mainly associated with internal acid‐base equilibrium of seawater CO2 systems, and nonthermal components mainly associated with external CO2 addition/removal using a global surface ocean climatological data set. We find that surface pH change is controlled by the balance between its thermal and nonthermal components, which are out of phase but comparable in magnitude. In contrast, surface Ω change is dominated by its nonthermal components, with its thermal components in phase and significantly smaller in magnitude. These findings explain why surface ocean pH and Ω are often out of phase in spatial patterns and seasonal cycles. When pH is primarily controlled by nonthermal components e.g., gas exchange, mixing and biology, pH and Ω will be in phase because their nonthermal components are intrinsically in phase. In comparison, when pH is primarily controlled by thermal components for example, rapid seasonal cooling or warming, pH and Ω will be out of phase because thermal and nonthermal components of pH are out‐of‐phase in nature.

Observations with the Rossi X-Ray Timing Explorer (RXTE), the Advanced Satellite for Astrophysics and Cosmology, and ROSAT have been used to search for X-ray emission produced by the inverse Compton process in the Abell 1367 galaxy cluster. The three data sets provide a high-quality spectrum which extends from 0.4 to 20 keV, allowing accurate separation of thermal and nonthermal components. In the cases of both the cluster's radio halo relic and radio galaxy 3C 264, the detection of nonthermal emission is model dependent. Nonthermal emission from the relic is detected using the RXTE Proportional Counter Array with a flux of ~0.010-0.019 photons cm-2 keV-1 s-1 at 1 keV, when the thermal emission is modeled with a single thermal component. However, modeling the thermal emission with two thermal components provides a better fit to the data and obviates the need for a nonthermal power-law component. We also find that thermal emission is a physically plausible origin for the second component. Using two thermal components to model the spectrum gives an upper limit of 3.3 × 10-3 photons cm-2 keV-1 s-1 on nonthermal X-ray emission from the radio relic region. We derive an average intracluster magnetic field of ≥0.84 μG for this region. This value is consistent with the radial field derived from Faraday rotation studies of noncooling flow clusters. For the central region of the intracluster medium, we find an upper limit of 1.08 × 10-3 photons cm-2 keV-1 s-1 at 1 keV for nonthermal emission. Joint fitting of the data sets gives a detection of nonthermal emission for 3C 264 of 1.21 × 10-4 to 2.45 × 10-4 photons cm-2 keV-1 s-1 at 1 keV, using a single thermal component. However, as with the radio relic region, two thermal components provide a much better fit to the spectrum and give an upper limit of less than 5.3 × 10-5 photons cm-2 keV-1 s-1 at 1 keV. Combining the X-ray upper limit with the radio spectrum gives an average magnetic field greater than 0.41 μG.

<p>Sea surface salinity (SSS) and Sea surface temperature (SST) are important measures of Ocean health. They provide information about ocean warming, atmospheric interactions, and acidification, with further effects on the global thermohaline circulation and as a consequence the global water cycle. Temperature and salinity can be linked to ecosystem productivity, can help to stratify different marine zones, while salinity can be used as a tracer for pollutants and is a measure of land influence in the ocean.</p><p>Satellite-derived ocean colour provides the opportunity to process data at a higher temporal and spatial resolution than in-situ monitoring, with its pointwise spatial data limitation, or that of traditional microwave remote sensing, with ocean colour satellites having pixel resolution on the tens to hundreds metre scale compared to microwave km scale.</p><p>This paper explores the methodology to extract SST and SSS from multispectral ocean radiance. Water leaving radiance is linked to the inherent optical properties of the water column, effected by the constituent parts for example from coloured dissolved organic matter, chlorophyll and total suspended matter. These parts contribute to the backscatter, absorption and reflectance coefficients, influencing the spectral signature of the radiance.</p><p> </p><p>The method uses temporally and spatially matched water data of SSS and SST in Patagonia, with spectral radiance. First ground level hyperspectral values are used to train a linear regression model. The model is then able to learn the relationship between the spectral input and SSS/SST values and accurately estimates SSS and SST in test regions using just the spectral signature as input.  Further work is also done on using principle component analysis to reduce the dimensionality of the inputs whilst maintaining predictive accuracy. Feature selection was also examined to understand the spectral bands with the strongest contribution to either the salinity or temperature values, to be used in selecting the band coefficients for converting to the multispectral satellite images. Then to increase the complexity of the model, machine learning algorithms (for example neural networks) are trained to be able to learn more complex relationships and predict values in different optical water types.</p><p>These models are tested using multispectral satellite images matched with the Patagonia field water data, to predict the oceanographic values from top of atmosphere (TOA) satellite image data.</p><p>This paper demonstrates a link between the ocean colour/ radiance values and the sea surface physical properties temperature and salinity, with a model accurately estimating SST and SSS from just radiance. This relationship between sea surface properties and spectral signatures is then tested in satellite ocean colour images which can be used to monitor these environmental properties with more regular temporal sampling, better spatial coverage and in previously inaccessible locations</p><p> </p><p>Acknowledgements: Jose Luis Iriarte for in-situ SST/SST data from Patagonia.</p>

Seasonal changes in sea surface temperature and salinity during the Little Ice Age in the Caribbean Sea deduced from Mg/Ca and 18O/16O ratios in corals

Mars exospheric thermal and non-thermal components: Seasonal and local variations

Currently, global sea surface salinity (SSS) can be retrieved by the satellite microwave radiometer onboard the satellite, such as the Soil Moisture and Ocean Salinity(SMOS) and the Aqurius. SMOS is an Earth Explorer Opportunity Mission from the European Space Agency(ESA). It was launched at a sun-synchronous orbit in 2009 and one of the payloads is called MIRAS(Microwave Imaging Radiometer using Aperture Synthesis), which is the first interferometric microwave radiometer designed for observing SSS at L-band(1.41 GHz).The foundation of the salinity retrieval by microwave radiometer is that the sea surface radiance at L-band has the most suitable sensitivity with the variation of the salinity. It is well known that the sensitivity of brightness temperatures(TB) to SSS depends on the sea surface temperature (SST), but the quantitative impact of the SST on the satellite retrieval of the SSS is still poorly known. In this study, we investigate the impact of the SST on the accuracy of salinity retrieval from the SMOS. First of all, The dielectric constant model proposed by Klein and Swift has been used to estimate the vertically and horizontally polarized brightness temperatures(TV and TH) of a smooth sea water surface at L-band and derive the derivatives of TV and TH as a function of SSS to show the relative sensitivity at 45° incident angle. Then, we use the GAM(generalized additive model) method to evaluate the association between the satellite-measured brightness temperature and in-situ SSS at different SST. Moreover, the satellite-derived SSS from the SMOS is validated using the ARGO data to assess the RMSE(root mean squared error). We compare the SMOS SSS and ARGO SSS over two regions of Pacific ocean far from land and ice under different SST. The RMSE of retrieved SSS at different SST have been estimated. Our results showed that SST is one of the most significant factors affecting the accuracy of SSS retrieval. The satellite-measured brightness temperature has a higher sensitivity with SSS variation and better accuracy of SSS retrieval at higher SST. For the most open oceans where surface salinity is typically greater than 32 psu, the sensitivity is around 0.2-0.25 K/psu for both vertical polarization and horizontal polarization when SST is 5°C,and the TB is more sensitive to the SSS for vertical polarization than horizontal polarization with the increase of SST. When SST increases to 30°C, the sensitivity is around 0.8 K/psu for vertical polarization which is about 40% larger than it of the horizontal polarization. In addition, the result of GAM model indicates that satellite-measured brightness temperature has better correlation with in-situ SSS at higher SST. The mean absolute error of the SMOS-derived SSS is around 0.9 psu when SST is 15°C, and decreases to 0.4 psu when the SST is 30°C.

Spatio-temporal dynamics of biogeochemical processes and air–sea CO2 fluxes in the Western English Channel based on two years of FerryBox deployment

Coral geochemical tracers have been used in studies of the paleoclimatology and paleoceanography of the tropics and subtropics. We measured Sr/Ca and oxygen isotope ratios (δ18O) in a coral sample collected from the southern part of Lombok Strait, a significant outlet of the Indonesian Throughflow (ITF) to the Indian Ocean, to reconstruct the historical record of sea surface temperature (SST) and seawater δ18O. Seawater δ18O can be used to approximate sea surface salinity (SSS) because it reflects the balance of evaporation and precipitation. The resulting time series reconstructed SST and SSS, covering the period 1962–2012, shows no clear trend of global warming, although the record includes a large cooling event (~4°C) during 1996–1997. Although neither SST nor SSS shows a systematic relationship with El Niño–Southern Oscillation and Indian Ocean Dipole (IOD), weak but significant correlations are found partly. In addition, the coral data show signals of major IOD and El Niño events in 1994 and 1997, respectively, although climatic trends recorded in the coral are not consistent with those found along the Java-Sumatra coast. To evaluate other influences on the ITF in Lombok Strait, we compared our coral record with coral records from sites in the Java Sea, the southern part of Makassar Strait, and Ombai Strait. During the northwest monsoon (December–January–February), variations in SST and SSS at Lombok Strait site are similar to those at the Java Sea and southern Makassar sites for the period 1962–1995, which suggests that low-salinity water from the Java Sea is carried at least to the southern part of Makassar Strait where it suppresses the ITF upstream from Lombok Strait. However, the SST and SSS records differ at the three sites during the southeast monsoon (June–July–August), indicating that surface conditions in Lombok Strait vary separately from those in the Java Sea. In the longer term, although global warming has been widely identified in the Indonesian Seas, the coral record shows no clear warming trend in the southern part of Lombok Strait, where fluctuations in the ITF may be modulating the distribution of heat in the surface waters of the western Pacific and eastern Indian Ocean.

We use geochemical and isotope measurements on a 225‐year old brain coral (Diploria labyrinthiformis) from the south shore of Bermuda (64°W, 32°N) to construct a record of decadal‐to‐centennial‐scale climate variability. The coral was collected alive, and annual density bands visible in X radiographs delineate cold and warm seasons allowing for precise dating. Coral skeletons incorporate strontium (Sr) and calcium (Ca) in relative proportions inversely to the sea surface temperature (SST) in which the skeleton is secreted. Previous studies on this and other coral colonies from this region document the ability to reconstruct mean annual and wintertime SST using Sr/Ca measurements (Goodkin et al., 2007, 2005). The coral‐based records of SST for the past 2 centuries show abrupt shifts at both decadal and centennial timescales and suggest that SST at the end of the Little Ice Age (between 1840 and 1860) was 1.5° ± 0.4°C colder than today (1990s). Coral‐reconstructed SST has a greater magnitude change than does a gridded instrumental SST record from this region. This may result from several physical processes including high rates of mesoscale eddy propagation in this region. Oxygen isotope values (δ18O) of the coral skeleton reflect changes in both temperature and the δ18O of seawater (δOw), where δOw is proportional to sea surface salinity (SSS). We show in this study that mean annual and wintertime δ18O of the carbonate (δOc) are correlated to both SST and SSS, but a robust, quantitative measure of SSS is not found with present calibration data. In combination, however, the Sr/Ca and δOc qualitatively reconstruct lower salinities at the end of the Little Ice Age relative to modern day. Temperature changes agree with other records from the Bermuda region. Radiative and atmospheric forcing may explain some of the SST variability, but the scales of implied changes in SST and SSS indicate large‐scale ocean circulation impacts as well.

Indonesian Throughflow (ITF), which is part of the global thermohaline circulation, is known to play an important role in the heat exchange between the Pacific and Indian Oceans. The flow of the ITF is highly complex, it depends on temperature and salinity. This study presents a proxy study from 25,000–18,000 years ago from two sites that are connected by the Indonesian Throughflow in the Makassar Strait. Oceanographic characteristics, including Sea Surface Temperature (SST) and Sea Surface Salinity (SSS) were reconstructed and analyzed during the Last Glacial Maximum (LGM) period. A 295 cm marine sediment core coded SO217-18522 (1°24.106'N; 119°04.781'E, water depth 978 m) and SO217-18519 (0°34.329'N; 118°06.859'E, water depth 1658 m) from the SONNE 217 research cruise in 2011 was used as research material. Oxygen isotope analysis, planktonic foraminiferal Mg/Ca geochemistry, and radiocarbon dating were used in this study. The SST reconstruction shows that the temperature during the LGM reach the minimum during ~20 ka BP and the SST value was significantly lower by ~2–3 °C compared to the Late Holocene value. The SST also shows significant cooler in marine sediment SO2017-8519 located in the southern site compared to the northern site. Salinity reconstructions during the LGM shows that SSS value was 0.82–1.13 psu higher than in the Holocene. The south–north gradients of SST and SSS in the Makassar Strait were larger over the 23.2–24.2 ka BP (SST gradient by 0.5–1 °C and SSS gradien by 1–1.7 psu) compared to the Late Holocene. The increase in SST and SSS gradients during the ~20 ka BP likely indicates a weakened intensity of the surface ITF relative to conditions during the Late Holocene.

Based on the data from the observation of the SNR G327.1-1.1 by ASCA and ROSAT, we find that G327.1-1.1 is a composite remnant with both a nonthermal emission component and a diffuse thermal emission component. The nonthermal component is well fitted by a power-law model with photon index about 2.2. This component is attributed to the emission from the synchrotron nebula powered by an undiscovered central pulsar. The thermal component has a temperature of about 0.4 keV. We attribute it to the emission from the shock-heat swept-up ISM. Its age, explosion energy and density of ambient medium are derived from the observed thermal component. Some charactistics about the synchrotron nebula are also derived. We search for the pulsed signal, but has not found it. The soft X-ray(0.4 - 2 keV) and hard X-ray(2 - 10 keV) images are different, but they both elongate in the SE-NW direction. And this X-ray SE-NW elongation is in positional coincidence with the radio ridge in MOST 843MHz radio map. We present a possibility that the X-ray nonthermal emission mainly come from the trail produced by a quickly moving undiscoverd pulsar, and the long radio ridge is formed when the pulsar is moving out of the boundary of the plerionic structure.

Observations of GRB 100724B with the Fermi Gamma-Ray Burst Monitor (GBM) find that the spectrum is dominated by the typical Band functional form, which is usually taken to represent a non-thermal emission component, but also includes a statistically highly significant thermal spectral contribution. The simultaneous observation of the thermal and non-thermal components allows us to confidently identify the two emission components. The fact that these seem to vary independently favors the idea that the thermal component is of photospheric origin while the dominant non-thermal emission occurs at larger radii. Our results imply either a very high efficiency for the non-thermal process, or a very small size of the region at the base of the flow, both quite challenging for the standard fireball model. These problems are resolved if the jet is initially highly magnetized and has a substantial Poynting flux.

We report on Suzaku and Chandra observations of the young supernova remnant CTB 37 B, from which TeV $\gamma$-rays were detected by the H.E.S.S. Cherenkov telescope. The 80 ks Suzaku observation provided us with a clear image of diffuse emission and high-quality spectra. The spectra revealed that the diffuse emission is comprised of thermal and non-thermal components. The thermal component can be represented by an NEI model with a temperature, a pre-shock electron density and an age of 0.9$\pm$0.2 keV, 0.4$\pm$0.1 cm$^{-3}$, and 650$^{+2500}_{-300}$yr, respectively. This suggests that the explosion of CTB 37 B occurred in a low-density space. A non-thermal power-law component was found from the southern region of CTB 37 B. Its photon index of $\sim$1.5 and a high roll-off energy ($>rsim$15 keV) indicate efficient cosmic-ray acceleration. A comparison of this X-ray spectrum with the TeV $\gamma$-ray spectrum leads us to conclude that the TeV $\gamma$-ray emission seems to be powered by either multi-zone Inverse Compton scattering or the decay of neutral pions. The point source resolved by Chandra near the shell is probably associated with CTB 37 B, because of the common hydrogen column density with the diffuse thermal emission. Spectral and temporal characteristics suggest that this source is a new anomalous X-ray pulsar.

Late Neogene planktonic foraminifera of the Cibao Valley (northern Dominican Republic): Biostratigraphy and paleoceanography

Abstract. Complex oceanic circulation and air–sea interaction make the eastern tropical Pacific Ocean (ETPO) a highly variable source of CO2 to the atmosphere. Although the scientific community have amassed 70 000 surface fugacities of carbon dioxide (fCO2) data points within the ETPO region over the past 25 years, the spatial and temporal resolution of this data set is insufficient to fully quantify the seasonal to interannual variability of the region, a region where fCO2 has been observed to fluctuate by > 300 μatm. Upwelling and rainfall events dominate the surface physical and chemical characteristics of the ETPO, with both yielding unique signatures in sea surface temperature and salinity. Thus, we explore the potential of using a statistical description of fCO2 within sea-surface salinity–temperature space. These SSS/SST relationships are based on in situ surface ocean CO2 atlas (SOCAT) data collected within the ETPO. This statistical description is then applied to high-resolution (0.25°) Soil Moisture and Ocean Salinity (SMOS) sea surface salinity (SSS) and Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) sea surface temperature (SST) in order to compute regional fCO2. As a result, we are able to resolve fCO2 at sufficiently high resolution to elucidate the influence that various physical processes have on the fCO2 of the surface ETPO. Normalised (to 2014) oceanic fCO2 between July 2010 and June 2014 within the entire ETPO was 39 (±10.7) μatm supersaturated with respect to 2014 atmospheric partial pressures, and featured a CO2 outgassing of 1.51 (±0.41) mmol m−2 d−1. Values of fCO2 within the ETPO were found to be broadly split between the Gulf of Panama region and the rest of the tropical eastern Pacific Ocean. The northwest, central and offshore regions were supersaturated, with wintertime wind-jet-driven upwelling found to constitute the first-order control on fCO2 values. This contrasts with the southeastern/Gulf of Panama region, where heavy rainfall combined with rapid stratification of the upper water column act to dilute dissolved inorganic carbon, and yield fCO2 values undersaturated with respect to atmospheric fugacities of CO2.