Adjacent Ocean Research Articles

Near shore distributions of phytoplankton and bacteria in relation to submarine groundwater discharge-fed fishponds, Kona coast, Hawai‘i, USA

Phytoplankton are important components of coastal marine ecosystems that are strongly influenced by freshwater inputs from land, including submarine groundwater discharge (SGD). Although SGD generates sharp onshore – offshore gradients in physical and chemical conditions at several locations around Hawaii Island little is known about the biotic responses of water column microbes to these conditions. We studied the distributions of phytoplankton and bacteria at two contrasting sites with SGD-fed fishponds, Kiholo and Kaloko Bay, including the full range of salinity extending from the fishponds to the coastal ocean. We addressed the hypotheses that (1) SGD-fed fishponds support a higher biomass and different composition of phytoplankton than the adjacent ocean, and (2) phytoplankton biomass and composition are related to SGD-driven salinity gradients in the coastal ocean. Phytoplankton biomass in fishponds was elevated (10–100-fold) and accompanied by higher average cell size pico- and nano-phytoplankton (2–6 μm) relative to sites outside the fishpond. General additive models (GAMs) showed elevated biomass and average cell size at mid-range salinities and declining biomass at salinity < 20 outside the fishponds. Multivariate RDA showed significant, site-specific relationships between surface phytoplankton biomass (Chl a), cell counts, and environmental parameters. Analysis of surface vs. deep samples from outside the fishponds showed elevated phytoplankton biomass at the surface, except in Kiholo lagoon where phytoplankton was elevated beneath the SGD-driven pycnocline. This study shows structuring of coastal phytoplankton through SGD inputs and suggest that changes in SGD due to coastal development or climate change can impact coastal marine ecosystems through effects on phytoplankton communities.

Distinctive Evolutions of Eurasian Warming and Extreme Events Before and After Global Warming Would Stabilize at 1.5 °C

AbstractUtilizing the specially designed low‐warming experiments of the fully coupled Community Earth System Model, we investigate the evolutions of Eurasian climate and extreme events if global mean temperature would stabilize at 1.5 °C and 2 °C above preindustrial levels or overshoot the 1.5 °C (1.5 °C OS) threshold. We find that distinctive evolutions of surface temperature (TS) and extreme events appear in different regions of Eurasia, particularly over East China and Northern Eurasia. In the course of global warming, before global mean temperature stabilizes, the two regions display similar changes of TS and extreme events. However, after global warming halts, the two regions experience distinctive evolutions of local warming and extreme events. Over East China, where the adjacent ocean exhibits stronger‐than‐global mean warming, the local TS and both the strength and frequency of heat extremes keep increasing continuously. The extreme precipitation intensity increases even more rapidly compared to the change of heat extremes. In stark contrast, TS and heat extremes intensity over northern Eurasia decrease in both the 1.5 °C and 1.5 °C OS cases, except that the extreme precipitation experiences little change. We find that the most vulnerable period over northern Eurasia is the transition period, in which TS increases till its maximum and then decreases. The heat extremes during the transition period are also stronger and more frequent compared to the end of the 21st century over northern Eurasia.

Mixing Estimates for Estuaries

AbstractThe well-known Knudsen relations and the total exchange flow (TEF) analysis framework provide quantifications of exchange flow across an open boundary to the adjacent ocean in terms of bulk values (Knudsen theory: inflow and outflow volume or salinity) or with resolution in salinity space (TEF: profiles of volume and salt flux in salinity coordinates). In the present study, these theories are extended toward mixing of salinity, defined as the decay of salinity variance due to turbulent mixing. In addition to the advective fluxes, diffusive fluxes across the boundary are also considered now. These new Knudsen and TEF relations for mixing are derived by applying Gauss’s theorem to the salinity square and salinity variance equations. As a result of the analysis, four different Knudsen relations for the mixing in estuaries are derived. The first one is exact and considers nonperiodicity as well as nonconstancy of the inflow and outflow salinities. The other three formulations are approximate only, in the sense that either nonperiodicity or nonconstancy or both are relaxed. The simplest of those formulations has recently been derived by MacCready et al. and estimates the estuarine mixing as the product of inflow salinity, outflow salinity, and time-averaged river runoff. These four mixing estimates are systematically assessed by means of a number of idealized estuarine test cases. For periodic tidal flow, the simplest estimate still predicts the effective (physical plus numerical) mixing within an error of about 10%.

Non-redfieldian mesopelagic nutrient remineralization in the eastern North Atlantic subtropical gyre

The eastern boundary of the North Atlantic subtropical gyre (NASTG) receives organic materials produced in the nearby Canary upwelling system (CanUS), which has important implications for the metabolic balance of the region. Here we computed absolute geostrophic, Ekman and eddy diffusive transports and net budgets of oxygen, nitrate, and phosphate, with an inverse model applied to annual climatologies from the World Ocean Atlas 2013, in a large box covering the eastern boundary of the NASTG. The surface waters (<100 m) of the box exported 4.2±1.1 mol O2 m−2 yr−1 to the adjacent ocean and atmosphere, and imported 0.40±0.17 mol N m−2 yr−1 and 22.2±9.5 mmol P m−2 yr−1 of nitrate and phosphate, respectively, indicating that net autotrophy prevailed in the euphotic waters of the eastern NASTG. The central, intermediate and deep waters (100 m-bottom) imported 6.7±3.3 mol O2 m−2 yr−1, and exported 1.05±0.35 mol N m−2 yr−1 and 50.2±21.8 mmol P m−2 yr−1 of nitrate and phosphate, respectively, indicative of net remineralization. Mesopelagic remineralization rates exceeded epipelagic net community production, implying a net deficit of carbon and nutrients in the region. Remineralization occurred at high N:P molar ratios (∼28) in central waters, and thus, a excess nitrate (DINxs = NO3-16·PO4) was produced at a rate of 2.2±1.6×1011 mol N yr−1. This excess nitrate was exported to the gyre interior, influencing the biogeochemistry of the whole NASTG and leaving the eastern margin with a strong nitrogen deficit, relative to carbon and phosphorus. According to the available literature, the organic carbon export from the CanUS could be sufficient to account for the carbon deficit, but the source of nitrogen remains elusive.

Terrain-Enhanced Precipitation Processes Above the Melting Layer: Results From OLYMPEX.

Enhancement of precipitation processes aloft over complex terrain is documented using reflectivity data from an S‐band scanning radar (NPOL) that was deployed on the west coast of Washington State during the Olympic Mountains Experiment (OLYMPEX). From November 2015 through mid‐January 2016, NPOL obtained high‐resolution data within sectors over the ocean and over the windward slopes of the Olympic Mountains. Contoured Frequency by Altitude Diagrams of radar reflectivity highlight a higher frequency of occurrence of larger reflectivities for all heights between 2 and 8 km over land compared to ocean, with the largest difference in the 4‐ to 6‐km range indicating a robust signature of enhancement aloft over the windward slopes. This enhancement pattern is found to some degree under all environmental conditions considered but is especially pronounced during periods of high vapor transport, high melting level height, southwest low‐level winds, and neutral stability. These conditions are generally associated with warm sectors of midlatitude cyclones and atmospheric rivers. Past studies have postulated that a secondary enhancement in reflectivity aloft was an intrinsic part of atmospheric river type systems. However, these results show that further significant enhancement of this signature occurs as deep moist‐neutral, high water vapor content flow is lifted when it encounters a mountain range. Reflectivity data from the dual‐precipitation radar aboard the Global Precipitation Measurement satellite also documents this reflectivity increase aloft over the Olympic Mountains compared to the adjacent ocean, showing the potential for Global Precipitation Measurement to provide reliable estimates of precipitation structure over remote mountainous regions.

Carbon pools and fluxes in the China Seas and adjacent oceans

The China Seas include the South China Sea, East China Sea, Yellow Sea, and Bohai Sea. Located off the Northwestern Pacific margin, covering 4700000 km2 from tropical to northern temperate zones, and including a variety of continental margins/basins and depths, the China Seas provide typical cases for carbon budget studies. The South China Sea being a deep basin and part of the Western Pacific Warm Pool is characterized by oceanic features; the East China Sea with a wide continental shelf, enormous terrestrial discharges and open margins to the West Pacific, is featured by strong cross-shelf materials transport; the Yellow Sea is featured by the confluence of cold and warm waters; and the Bohai Sea is a shallow semi-closed gulf with strong impacts of human activities. Three large rivers, the Yangtze River, Yellow River, and Pearl River, flow into the East China Sea, the Bohai Sea, and the South China Sea, respectively. The Kuroshio Current at the outer margin of the Chinese continental shelf is one of the two major western boundary currents of the world oceans and its strength and position directly affect the regional climate of China. These characteristics make the China Seas a typical case of marginal seas to study carbon storage and fluxes. This paper systematically analyzes the literature data on the carbon pools and fluxes of the Bohai Sea, Yellow Sea, East China Sea, and South China Sea, including different interfaces (land-sea, sea-air, sediment-water, and marginal sea-open ocean) and different ecosystems (mangroves, wetland, seagrass beds, macroalgae mariculture, coral reefs, euphotic zones, and water column). Among the four seas, the Bohai Sea and South China Sea are acting as CO2 sources, releasing about 0.22 and 13.86– 33.60 Tg C yr−1 into the atmosphere, respectively, whereas the Yellow Sea and East China Sea are acting as carbon sinks, absorbing about 1.15 and 6.92 –23.30 Tg C yr−1 of atmospheric CO2, respectively. Overall, if only the CO2 exchange at the sea-air interface is considered, the Chinese marginal seas appear to be a source of atmospheric CO2, with a net release of 6.01 –9.33 Tg C yr−1 , mainly from the inputs of rivers and adjacent oceans. The riverine dissolved inorganic carbon(DIC) input into the Bohai Sea and Yellow Sea, East China Sea, and South China Sea are 5.04, 14.60, and 40.14 Tg C yr−1 , respectively. The DIC input from adjacent oceans is as high as 144.81 Tg C yr−1 , significantly exceeding the carbon released from the seas to the atmosphere. In terms of output, the depositional fluxes of organic carbon in the Bohai Sea, Yellow Sea, East China Sea, and South China Sea are 2.00, 3.60, 7.40, and 5.92 Tg C yr−1 , respectively. The fluxes of organic carbon from the East China Sea and South China Sea to the adjacent oceans are 15.25–36.70 and 43.93 Tg C yr−1 , respectively. The annual carbon storage of mangroves, wetlands, and seagrass in Chinese coastal waters is 0.36 –1.75 Tg C yr−1 , with a dissolved organic carbon (DOC) output from seagrass beds of up to 0.59 Tg C yr−1 . Removable organic carbon flux by Chinese macroalgae mariculture account for 0.68 Tg C yr−1 and the associated POC depositional and DOC releasing fluxes are 0.14 and 0.82 Tg C yr−1 , respectively. Thus, in total, the annual output of organic carbon, which is mainly DOC, in the China Seas is 81.72 –104.56 Tg C yr−1 . The DOC efflux from the East China Sea to the adjacent oceans is 15.00 –35.00 Tg C yr−1 . The DOC efflux from the South China Sea is 31.39 Tg C yr−1 . Although the marginal China Seas seem to be a source of atmospheric CO2 based on the CO2 flux at the sea-air interface, the combined effects of the riverine input in the area, oceanic input, depositional export, and microbial carbon pump (DOC conversion and output) indicate that the China Seas represent an important carbon storage area.

Response of the atmospheric hydrological cycle over the tropical Asian monsoon regions to anthropogenic aerosols and its seasonality

This study investigates the impact of anthropogenic aerosols on the atmospheric hydrological cycle over the tropical Asian monsoon region (South Asian, Southeast Asian, and western North Pacific monsoons), using a coupled atmosphere-ocean global climate model (CGCM), Model for Interdisciplinary Research on Climate-Earth System Models. Three-ensemble historical (HIST) and sensitivity (piAERO) experiments for the period 1985–2005 are conducted. The piAERO experiment is the same as HIST, but with anthropogenic aerosol emissions kept at preindustrial values. The results show that, as a whole, the Asian monsoon precipitation is reduced by the increase in aerosol loading during boreal summer and winter. This decrease in precipitation corresponds to a decrease in precipitable water due to the cooling in surface air temperature (SAT), mainly over adjacent oceans. The cooling is explained by the sum of the direct and indirect effects of aerosols. A modulation of the Walker circulation occurs, which can be explained by the east-west horizontal SAT gradient over the tropics due to the spatially heterogeneous increase in aerosols. Concurrent with the modulation of the Walker circulation, the anomalous descending motions over the tropical Asian monsoon region are consistent with the decrease in precipitation. In addition, the changes in local Hadley circulation (or a shift of the inter-tropical convergence zone) are unclear over the Asian monsoon region and thus cannot explain the decrease in precipitation. Moreover, the detailed spatial pattern of the response of the atmospheric hydrological cycle over the Asian monsoon region has distinct seasonality. Interestingly, signals are distinct in regions where tropical disturbance activity is vigorous during both boreal summer and winter. However, uncertainties regarding aerosol-cloud-precipitation interactions in current climate models and internal variability in the climate models may have affected the results.

Relationships between pacific and atlantic ocean sea surface temperatures and water levels from satellite altimetry data in the Amazon rivers

ABSTRACT The influence of SST (Sea Surface Temperature) of adjacent oceans on the variability of water levels in the Amazon basin was investigated by using radar altimetry from the ENVISAT and Jason-2 missions. Data from the in situ network was used to compare the correlations of water level and SST anomalies in the sub-basins of the Amazonas-Peru, Solimões, Negro and Madeira Rivers. The analysis was made on the monthly and annual scales between 2003 and 2015. The correlations with anomalies of levels from altimetry presented higher accuracy indices than those from the conventional network. In general, ATN and PAC are better correlated with the entire basin. During the flood months, most of the sub-basins presented negative associations with ATN. In the months of ebb, the response to the indexes varies according to the region. The satellite altimetry data permitted to reach regions non-monitored by the conventional network. We also analyzed the impacts of hydrological extremes in all these sub-regions in the last 13 years. In Western Amazon, the drought of 2010 stands out, associated with the warming of the Tropical Atlantic and the El Niño. In the Negro River, the water level anomalies were the lowest in the basin during the 2005 drought. In the Purus River, the effects of the 2010 drought that affected the entire Amazon, were higher in 2011 due to its strong relationship with the Atlântic and Pacific oceans. In general, hydrological extremes are stronger or highlighted when SST increases simultaneously in both oceans.

Origins and discrimination between local and regional atmospheric pollution in Haiphong (Vietnam), based on metal(loid) concentrations and lead isotopic ratios in PM10.

Southeast Asia is a hotspot of anthropogenic emissions where episodes of recurrent and prolonged atmospheric pollution can lead to the formation of large haze events, giving rise to wide plumes which spread over adjacent oceans and neighbouring countries. Trace metal concentrations and Pb isotopic ratios in atmospheric particulate matter < 10μm (PM10) were used to track the origins and the transport pathways of atmospheric pollutants. This approach was used for fortnightly PM10 collections over a complete annual cycle in Haiphong, northern Vietnam. Distinct seasonal patterns were observed for the trace metal concentration in PM10, with a maximum during the Northeast (NE) monsoon and a minimum during the Southeast (SE) monsoon. Some elements (As, Cd, Mn) were found in excess according to the World Health Organization guidelines. Coal combustion was highlighted with enrichment factors of As, Cd, Se, and Sb, but these inputs were outdistanced by other anthropogenic activities. V/Ni and Cu/Sb ratios were found to be markers of oil combustion, while Pb/Cd and Zn/Pb ratios were found to be markers of industrial activities. Pb isotopic composition in PM10 revealed an important contribution of soil dusts (45-60%). In PM10, the Pb fraction due to oil combustion was correlated with dominant airflow pathways (31% during the north-easterlies and 20% during the south-easterlies), and the Pb fraction resulting from industrial emissions was stable (around 28%) throughout the year. During the SE monsoon, Pb inputs were mainly attributed to resuspension of local soil dusts (about 90%), and during the NE monsoon, the increase of Pb inPM10 was due to the mixing of local and regional inputs.

Hydrographic features of the Yongle blue hole in the South China Sea and their influential factors

A study of the hydrographic features of the Yongle blue hole (YLBH) in the South China Sea has been conducted using an extensive set of hydrological data collected in October, 2016. Observations include water column measurements of temperature, salinity, density, chlorophyll-a ( Chl -a), dissolved oxygen (DO), turbidity, grain size of suspended particulate matter (SPM) and tidal currents. The variability of tidal currents indicates that the YLBH has no large-scale connection with the adjacent ocean. Four thermoclines were observed in the YLBH at depths of 3, 10, 50 and 80–110 m. The water column was most stratified at 50 m depth and was homogeneous below 155 m depth. A subsurface Chl -a maximum was present at 10–20 m depth, and an additional peak of Chl -a coincided with the deepest thermocline at 90 m depth. A high concentration of DO was present at the surface with values up to 7 mg/L, and concentrations decreased sharply at the thermoclines becoming 0 mg/L below approximately 90 m. Turbidity seems to vary with Chl -a, namely high values at depths of 10–20 m and approximately 90 m. The SPM in the YLBH had two major components in terms of grain size (5.28–38.55 and 145–500 μm). The volume concentration of the coarser component was 2–3 orders of magnitude higher than the finer component. A θ - S diagram indicates that the water properties below 80 m were distinct from the upper water column. The thermoclines above 80 m exhibit diurnal and seasonal variability, suggesting that the vertical circulation could reach as deep as a permanent thermocline at 80 m depth, that restricts water exchange between the upper water column and water below 80 m. In addition, the supply of DO from the atmosphere was inhibited by the permanent thermocline, which contributes to the formation of anoxic water below approximately 90 m. Concentration of the finer component of SPM dominated the turbidity signal in the YLBH, suggesting that the finer component was mainly composed of sediment, and the coarser component might be dominated by algae and marine snow.

Opposite Aerosol Index-Cloud Droplet Effective Radius Correlations Over Major Industrial Regions and Their Adjacent Oceans.

The Moderate Resolution Imaging Spectroradiometer (MODIS) C6 L3 and the European Centre for Medium‐Range Weather Forecasts (ECMWF) ERA‐Interim reanalysis data from 2003 to 2016 are employed to study aerosol‐cloud correlations over three industrial regions and their adjacent oceans, as well as explore the impact of meteorological conditions on the correlations. The analysis focusing on liquid and single‐layer clouds indicates an opposite aerosol‐cloud correlation between land and ocean; namely, cloud effective radius is positively correlated with aerosol index over industrial regions (positive slopes), but negatively correlated over their adjacent oceans (negative slopes), for a quasi‐constant liquid water path. The positive slopes are relatively large under low lower‐tropospheric stability (LTS; weakly stable condition), but much weaker or even become negative under high LTS (stable conditions) and high liquid water path. The occurrence frequency of cloud top height (CTH) and LTS suggests that positive correlations are more likely corresponding to relatively high CTH and low LTS, while negative to low CTH and high LTS.

Strengthening of the East Asian winter monsoon during the mid-Holocene

The change in the East Asian winter (December–January–February) monsoon (EAWM) during the mid-Holocene, approximately 6000 years ago, was investigated using all available experiments within the Paleoclimate Modelling Intercomparison Project (PMIP). As defined by regional-averaged meridional wind speed at 850 hPa, the mid-Holocene EAWM intensity was consistently stronger than that of the reference period in 38 out of the 42 models chosen for analysis, with an average strengthening of 14% across all models. In response to changes in the Earth’s orbital parameters and atmospheric greenhouse gas concentrations, zonal and meridional land–sea thermal contrasts and sea-level pressure gradients were enhanced between the continent and the adjacent oceans of East Asia, leading to the strengthening of the mid-Holocene EAWM. In addition, there were uncertainties regarding the EAWM reconstructions and the effect of dynamic ocean and vegetation on the EAWM change during the mid-Holocene.

Three-dimensional exchange flows in a semi-enclosed bay: Numerical simulations and high frequency radar observations

In this work we present the exchange flows between a semi-enclosed Bay and the adjacent ocean as measured by a real-time coastal observing system in Baja California, Mexico. Several sources of information as numerical modeling, currents profile data, high frequency radar observations and drifters tracking, all together show an interesting three-dimensional structure to the exchange flows. The northern entrance (relatively shallow, ∼40 m at its deepest portion) showed an estuarine-like exchange pattern, with a net outflow at the shallow parts and inflow at the deepest, suggesting that the frictional effect is more important than the earth's rotation, as typically observed in relatively small bodies of water like estuaries and coastal lagoons. On the other hand, the southern entrance (with a ∼400 m deep canyon) is more complex, with recurrent anticyclonic exchange pattern with inflows at the western limit and outflows at the east. We suggest that the vertical structure of this circulation may be sustained by the deep canyon which lowers the thermocline, but further investigation is needed.

Potential regulation on the climatic effect of Tibetan Plateau heating by tropical air–sea coupling in regional models

Based on the conventional weather research and forecasting (WRF) model and the air–sea coupled mode WRF-OMLM, we investigate the potential regulation on the climatic effect of Tibetan Plateau (TP) heating by the air–sea coupling over the tropical Indian Ocean and western Pacific. Results indicate that the TP heating significantly enhances the southwesterly monsoon circulation over the northern Indian Ocean and the South Asia subcontinent. The intensified southwesterly wind cools the sea surface mainly through the wind-evaporation-SST (sea surface temperature) feedback. Cold SST anomaly then weakens monsoon convective activity, especially that over the Bay of Bengal, and less water vapor is thus transported into the TP along its southern slope from the tropical oceans. As a result, summer precipitation decreases over the TP, which further weakens the TP local heat source. Finally, the changed TP heating continues to influence the summer monsoon precipitation and atmospheric circulation. To a certain extent, the air–sea coupling over the adjacent oceans may weaken the effect of TP heating on the mean climate in summer. It is also implied that considerations of air–sea interaction are necessary in future simulation studies of the TP heating effect.

A \u201cLa Ni\xf1a-like\u201d state occurring in the second year after large tropical volcanic eruptions during the past 1500\xa0years

Using an ensemble of nine El Niño/Southern Oscillation (ENSO) reconstructed proxies and volcano eruption proxies for the past 1500 years, this study shows that a significant La Niña state emerges in the second year (year (2) hereafter) after large tropical volcanic eruptions. The reasons for the development of La Niña are investigated using the Community Earth System Model (CESM). In the volcanic eruption experiment (Vol), a robust La Niña signal occurs in year (2), resembling the proxy records. The eastward positioning of the western North Pacific anomalous anticyclone (WNPAC) in Vol plays a critical role in the advanced decay of year (2) warming and the strong intensification of cooling in the equatorial eastern Pacific. The enhanced easterlies located on the southern edge of the WNPAC can stimulate consecutive oceanic upwelling Kelvin waves, shallowing the thermocline in the eastern Pacific, thereby resulting in a greater cooling rate by the enhanced thermocline feedback and cold zonal advection. Over the equatorial eastern Pacific, the reduced shortwave radiation contributes to the advanced decay of warming, while the upward latent heat flux augments the strong intensification of the cooling. Essentially, the eastward positioning of the WNPAC is a result of the volcanic forcing. The volcanic effect cools the maritime continent more than its adjacent oceans, thus pushing convective anomalies eastward during year (1). This induces vertical thermal advection and upward surface latent heat flux, thereby suppressing the development of warm Sea Surface Temperature over the central-western Pacific and causing the eastward positioning of the WNPAC in Vol.

Role of Eastern Ghats Orography and Cold Pool in an Extreme Rainfall Event over Chennai on 1 December 2015

Chennai and its surrounding region received extreme rainfall on 1 December 2015. A rain gauge in the city recorded 494 mm of rainfall within a span of 24 h—at least a 100-yr event. The convective system was stationary over the coast during the event. This study analyzes how the Eastern Ghats orography and moist processes localized the rainfall. ERA-Interim data show a low-level easterly jet (LLEJ) over the adjacent ocean and a barrier jet over the coast during the event. A control simulation with the nonhydrostatic Weather Research and Forecasting (WRF) Model shows that the Eastern Ghats obstructed the precipitation-driven cold pool from moving downstream, resulting in the cold pool piling up and remaining stationary in the upwind direction. The cold pool became weak over the ocean. It stratified the subcloud layer and decelerated the flow ahead of the orography; hence, the flow entered a blocked regime. Maximum deceleration of the winds and uplifting happened at the edge of the cold pool over the coast. Therefore, a stationary convective system and maximum rainfall occurred at the coast. As a result of orographic blocking, propagation of a low pressure system (LPS) was obstructed. Because of the topographic β effect, the LPS subsequently traveled a southward path. In a sensitivity experiment without the orography, the cold pool was swept downstream by the winds; clouds moved inland. In the second experiment with no evaporative cooling of rain, the cold pool did not form; flow, as well as clouds, moved over the orography.

Miocene Oceanographic Evolution Based on the Sr and Nd Isotope Record of the Central Mediterranean

AbstractThe Miocene is a key interval in the geodynamic and oceanographic evolution of the Mediterranean marking the transition from a wide open basin to the modern closed basin. We used the Sr and Nd isotope records of two Miocene carbonate successions in the Adriatic to document that the evolution of the Mediterranean Basin controlled its seawater chemistry. During the late Aquitanian (~21 Ma), a time of glaciation and sea level lowstand, increased runoff affected the Sr isotope ratios of Mediterranean waters, whereas during the Burdigalian (20.44–15.97 Ma) volcanism in the circum‐Mediterranean area mainly influenced the Sr isotopic signature. During the Langhian (15.97–13.82 Ma), a time of sea level highstand associated with the Middle Miocene Climatic Optimum, the Nd isotope values indicate that waters exchanged between the Paratethys and the Central Mediterranean. The Central Mediterranean was well connected with the Atlantic Ocean between the Langhian and the early Tortonian (15.97–11.5 Ma), but exchange of water with the Paratethys declined. In the Messinian (6.3 Ma), connections between some marginal Mediterranean basins, for example, the proto‐Adriatic basin, and the Central Mediterranean, became restricted. In this basin, the Sr isotope values fell below the global reference line, while Nd isotope ratios show a strong affinity with the Atlantic Ocean and also indicate freshwater input. We conclude that the Mediterranean Nd isotope signature differs from that in the open oceans and reflects the basin physiography, reflecting a mix of signals derived from the adjacent oceans and local signals.

Small-scale fisheries under climate change in the Pacific Islands region

For Pacific Island communities, social change has always been a part of their socio-political lives, while environmental changes were always transient and reversible, so that they understood and engaged with their ocean as a provider for food, culture and life. However, recent unprecedented and irreversible changes brought on by global climate change challenge this norm and alter their lagoons and adjacent oceans into unfamiliar territories. Climate change already is affecting, and has been projected to continue to disproportionately impact, Pacific Island Countries and Territories (PICTs) through rising temperatures, sea-level rise, saltwater intrusion of freshwater resources, coastal erosion, an increase in extreme weather events, altered rainfall patterns, coral reef bleaching, and ocean acidification. While knowledge is building about potential impacts on ecosystems and some target stocks, there is little information available for communities, governments and regional institutions on how to respond to these changes and adapt. What are the consequences for marine conservation, fisheries management and coastal planning at local, national and regional scales? What strategies and policies can best support and enable responses to these challenges across different scales? What opportunities exist to finance necessary climate change adaptation and mitigation measures? To consider these urgent issues, this paper synthesises innovative research methods, and studies many of the looming scientific, policy and governance challenges from a diversity of perspectives and disciplines.

Flood protection for the City of Beira

AbstractA new tidal outlet is now protecting the port city on Mozambique's Indian Ocean coast with a population of approximately half a million people, and improving the city's drainage. Since the Indian Ocean in this area has a very large tidal range of up to 7 m, reliable coastal protection is of great importance. The Chiveve tidal river, which runs through the city for a distance of approx. 5 km, was neglected in the past, and became increasingly silted up, to the point that it no longer served as a drainage channel for the surrounding area. The standing water promoted the spreading of diseases such as malaria and cholera. During very high tides or storm surges in the adjacent ocean, combined with heavy rainfall, the Chiveve regularly overflowed its banks and flooded much of its catchment area – particularly the informal settlements along its banks. To address this problem, Inros Lackner designed a new tidal outlet and flood barrier to protect Beira's city centre. The project also included a comprehensive plan for the reestablishment of the original river course and renaturation measures along its embankments. This included excavation of the river, dredging of sludge within the fishing port downstream, resettlement measures, and planting of young mangroves along the river banks.

Winds: intensity and power density simulated by RegCM4 over South America in present and future climate

Since wind is an important source of renewable energy, it has attracted attention worldwide. Several studies have been developed in order to know favorable areas where wind farms can be implemented. Therefore, the purpose of this study is to project changes in wind intensity and in wind power density (PD), at 100 m high, over South America and adjacent oceans, by downscaling and ensemble techniques. Regional climate model version 4 (RegCM4) was nested in the output of three global climate models, considering the RCP8.5 scenario. RegCM4 ensemble in the present climate (1979–2005) was validated through comparisons with ERA-Interim reanalysis. The ensemble represents well the spatial pattern of the winds, but there are some differences in relation to the wind intensity registered by ERA-Interim, mainly in center-east Brazil and Patagonia. The comparison between the future climate (2020–2050 and 2070–2098) and the present one shows that there is an increase in wind intensity and PD on the north of SA, center-east Brazil (except in summer) and latitudes higher than 50°S. Such increase is more intense in the period 2070–2098.