Ocean heat and carbon are transported through the Florida Straits, contributing to the Atlantic Meridional Overturning Circulation, and playing an important role in climate. Insufficient observations ...of carbonate chemistry within the Florida Straits have limited our understanding of ocean acidification within this region. To examine carbonate chemistry and carbon transport dynamics within this region, we developed an algorithm to estimate dissolved inorganic carbon (DIC) using more routinely measured input parameters (temperature, salinity, and dissolved oxygen DO) and the corresponding sampling date, depth, and longitude. The developed DIC algorithm output demonstrates good agreement with limited existing in situ observations. By applying this algorithm, we developed a seasonally resolved time series of DIC spanning from 2002 to 2018 for the Florida Straits at 27°N. This time series suggests that short‐term variations in surface water DO and DIC were strongly influenced by the Florida Current transport. The long‐term increase in DIC was mainly caused by anthropogenic carbon accumulation and DO decrease. The highest increasing rate in DIC was found in North Atlantic Central Water where DO decrease was fastest while the decreasing rate in pH was highest in Antarctic Intermediate Water (AAIW) because of the lower buffer capacity of this water mass. The long‐term pH decrease, especially in AAIW, can impact the health of deep corals in the Florida Straits. Quantifying carbon transport between the coast of Florida and the Bahamas is important to understanding the carbonate chemistry dynamics and the long‐term acidification of this important region.
Plain Language Summary
A large amount of ocean heat and carbon is transported northward through the Florida Straits, the upper limb of the Atlantic Meridional Circulation, and plays a role in ocean carbonate chemistry along the U.S. east coast. Our understanding of carbon transport and ocean acidification in the Florida Straits is limited by insufficient carbonate chemistry data within this region. To address this issue, we developed an algorithm based on high‐quality data from carbonate chemistry‐focused research cruises. Then we applied this algorithm to seasonally resolved hydrographic time‐series data from 2002 to 2018 to generate the carbonate chemistry datasets for the study region. We found that short‐term variation in surface water dissolved oxygen was strongly correlated with volume transport. During the past two decades, dissolved oxygen showed a significant decreasing trend, and dissolved inorganic carbon showed a significant increasing trend. In addition, the increasing rate of dissolved inorganic carbon was highest in North Atlantic Central Water where the decreasing rate in dissolved oxygen was greatest. Furthermore, the long‐term declines in pH and aragonite saturation state have the potential to threaten the health of corals living in the Florida Straits.
Key Points
Short‐term variations in surface water oxygen and dissolved inorganic carbon concentrations are strongly influenced by the Florida Current transport
Anthropogenic carbon accumulation and dissolved oxygen decrease are two main factors that lead to the long‐term increase in dissolved inorganic carbon of the Florida Straits
The highest long‐term rate of increase in dissolved inorganic carbon of North Atlantic Central Water is likely due to the highest rate of increase in respiration
Detailed pathway of wave energy exchange between the Pacific and Indian Oceans through the Indonesian archipelago for a wide range of wave frequency is investigated using a reduced gravity model with ...realistic coastline. The wave energy flux analysis that can be applicable for all latitudes in a linear shallow water system is adopted. The energy fluxes diagnosed from the model outputs for the incoming Rossby waves from the Pacific clearly indicate two major energy pathways to the Indian Ocean: one turning southward in the Halmahera Sea and reaches the Indian Ocean via the Banda Sea and the Timor Passage, and the other passing through the Makassar and Lombok Straits. The former route, however, is shifted to the western side of the island chain within the Banda Sea due to energy trapping around the island chain. It is also found that strong energy dissipation occurs along the northern coast of New Guinea when the incoming wave period is shorter than 1.5 years. In the case of the Kelvin waves from the Indian Ocean, it is found that the major energy pathway is through the Lombok and Makassar Straits to the Pacific Ocean. However, there appears another pathway along the eastern side of the Sulawesi Island in the Banda Sea to exit through the Molucca Sea only when the wave period is shorter than about one month. This secondary pathway makes it easier for the wave energy from the Indian Ocean to reach the western Pacific Ocean for the short-period waves.
High resolution and precise records of the carbon isotopic composition of atmospheric carbon dioxide from ice cores are now providing a valuable constraint on the origin of the rise in CO2 over the ...last deglaciation. Previous studies using isotopic measurements on the tests of planktonic foraminifera from marine sediments had shown a deglacial minimum in the carbon isotopic composition of seawater carbon in the surface and thermocline waters of the Southern Hemisphere and the tropics, a feature also seen in the atmospheric record. Here we show that this deglacial minimum also can be clearly seen in carbon isotope measurements on planktonic foraminifera from sediment cores in the North Atlantic. There are also new high-resolution and precise records of the carbon isotopic composition of intermediate and mode waters generated using benthic foraminifera which show a history of change that is strikingly similar to that in the atmosphere. Similarities in these new highly-resolved deglacial records suggest that air–sea exchange can effectively globalize the isotopic signature of a release of carbon from the deep ocean. This limits the utility of carbon isotopes for constraining the precise location and mechanism of carbon release, indicating that more direct nutrient tracers are needed. However, given that the equilibrium partitioning of carbon isotopes between the atmosphere and ocean is temperature dependent, the difference between the atmosphere and upper ocean values could potentially provide an independent estimate of sea surface temperature change.
•A deglacial carbon isotope minimum is observed in surface waters of the North Atlantic.•Deglacial δ13C of well-ventilated intermediate and mode waters mirrors the atmosphere.•Air–sea exchange globalizes the isotopic signature of the release of deep ocean carbon.•Ocean–atmosphere δ13C difference records temperature of equilibration.
Indonesia is exposed to earthquakes, volcanic activities, and associated tsunamis. This is particularly the case for Lombok and Sumbawa Islands in West Nusa Tenggara, where evidence of tsunamis is ...frequently observed in its coastal sedimentary record. If the 1815 CE Tambora eruption on Sumbawa Island generated a tsunami with well-identified traces on the surrounding islands, little is known about the consequences of the 1257 CE tremendous eruption of Samalas on the neighboring islands, and especially about the possible tsunamis generated in reason of a paucity of research on coastal sedimentary records in this area. However, on Lombok Island, the eruption of the Samalas volcano produced significant volumes of pyroclastic flows that entered the sea in the North and East of the island. These phenomena must have produced a tsunami that left their traces, especially on Sumbawa Island, whose western coastline is only 14 km away from Lombok’s eastern shore. Therefore, the main goal of this study is to investigate, find evidence, and determine the age of marine-origin sediments along the shore of the Alas Strait, Indonesia. We collected and analyzed samples of coral and seashells from marine deposits identified along the west coast of Sumbawa, i.e., in Belang Island and abandoned fishponds in Kiantar Village, in order to identify the sources and the occurrence period of these deposits events. Based on the radiocarbon dating of coral and seashell samples, we concluded that none of the identified marine deposits along the western coast of Sumbawa could be related chronologically to the 1257 CE eruption of Samalas. However, possible tsunami deposits located in Belang Island and abandoned fishponds in Kiantar Village yielded 4th century CE, 9th century CE, and 17th century CE. We also conclude that past large earthquakes triggered these tsunamis since no known volcanic eruption occurred near the Alas Strait at that time that may have triggered a tsunami.
Straits are both a choke point and passage through which material and energy are exchanged between two adjoining water bodies. Understanding the mechanisms that drive these exchanges therefore is ...vital to quantifying the water and sediment budgets in regional and global oceans. Here we present a study in which a novel, phase‐averaging method was employed to better estimate the net‐suspended sediment fluxes through the entire Bohai Strait, the only passage for the massive Yellow River‐delivered sediment to leave the enclosed Bohai Sea for the open Yellow Sea. In winter, the transport through the strait was nearly barotropic in waters well mixed by the energetic winter monsoons. The transport became primarily baroclinic (opposite directions between upper and lower layers) in spring due to stratification, especially in the southern part of the strait. Intermittent but frequent southerly winds in northerly dominated winters were responsible for a net westward sediment transport into the Bohai Sea, a finding contrary to a status quo view. Hence, previous studies in which these intermittent southerly wind busts were not included are believed to have overestimated the sediments export from the Bohai Sea.
Plain Language Summary
Water and sediment transport through a strait (a natural and narrow waterway that connects two larger water bodies) is important for global oceanographic circulation and biogeochemical processes. The residual current is a continuous movement of seawater that plays an important role in sediment transport. Profiles of residual currents across the entire strait are indispensable for estimating these transports but extremely difficult to obtain especially in tidal coastal ocean. Here we present data from two cruises of repeated surveys that produced these residual current profiles across the Bohai Strait, with the help of a novel detiding scheme. The sediment flux through the Bohai Strait is in opposite directions between upper and lower layers in late spring but unidirectional throughout the entire water column in winter. Even intermittent southerly winds in northerly dominated winters can cause a net sediment import into the semienclosed Bohai Sea through most of the strait, which is different from the long‐held view of winter transport through the Bohai Strait.
Key Points
Profiles of residual current across the entire Bohai Strait were surveyed for the first time using the phase‐averaging method (PAM)
Intermittent southerly winds in northerly dominated winters caused a net sediment transport into the Bohai Sea through the strait
The sediment fluxes through the Bohai Strait were primarily baroclinic in late spring but barotropic in winter
•Effects of the Turkish Straits System on the phylogeography of Merlangius merlangus.•High levels of genetic differentiation between the Black Sea and the North Aegean samples.•Different conservation ...strategies will be necessary for species and stock protection.
In this study, the taxonomic resolution and phylogenetic relationship of two presumed subspecies of Merlangius merlangus, namely M. m. euxinus and M. m. merlangus, were investigated. In addition, the effect of the Turkish Straits System on the evolutionary history and genetic structure of M. merlangus, was explored. The mitochondrial cytochrome c oxidase subunit 1 and cytochrome b genes, and the nuclear recombination activating gene-1 were analysed. Our results indicate no clear distinction between the two presumed subspecies, which is attributed to the low resolution of recombination activating gene-1 and/or presence of potential gene flow between the two subspecies. The temporal pattern of divergence between the two presumed subspecies related to the Last Glacial Maximum (219 Kya), whereas the expansion of each main sampling location occurred after the flooding of the Black Sea by salt water from the Mediterranean (5 Kya), following a period of stability. Additionally, significant genetic differences are observed among the North Aegean samples and the collections from the Turkish Straits System and the Black Sea, along with some significant structure among sampling sites located in the Turkish Straits System and Black Sea. The lower genetic variability of the eastern Mediterranean M. merlangus when compared to Atlantic ones might be due to a potential population bottleneck before the last glacial period, a trend that is commonly found in these waters.
Calving events of Petermann Glacier, northwest Greenland, in 2010 and 2012 reduced the length of its ice tongue by c. 25 km, allowing exploration of newly uncovered seafloor during the Petermann 2015 ...Expedition. This article presents the results of foraminiferal analysis and environmental data from thirteen surface sediment samples in northern Nares Strait and Petermann Fjord, including beneath the modern ice tongue. This is the first study of living foraminifera beneath an arctic ice tongue and the first modern foraminiferal data from this area. Modern assemblages were studied to constrain species environmental preferences and to improve paleoenvironmental interpretations of foraminiferal assemblages. Sub-ice tongue assemblages differed greatly from those at all other sites, with very low faunal abundances and being dominated by agglutinated fauna, likely reflecting low food supply under the ice tongue. Fjord fauna were comprised of 80 percent or more calcareous species. Notably, Elphidium clavatum is absent beneath the ice tongue although it is dominant in the fjord. Increasing primary productivity associated with the transition to mobile sea ice, diminishing influence of the Petermann Glacier meltwater with distance from the grounding line, and increased influence of south-flowing currents in Nares Strait are the important controls on the faunal assemblages.
The summer upwelling of the Eastern Aegean Sea is investigated by daily night-time MODerate resolution Imaging Spectroradiometer Sea Surface Temperature scenes in the periods from June to November ...(extended summer) 2003-2015. The analysis is supported by wind data downloaded from the European Centre for Medium-Range Weather Forecasts Re-Analysis archive. On average over these summers, upwelling and Etesian wind occurred 69% and 78% of time, respectively. The highest correlation between upwelling and wind was found from June to September, with the beginning of the upwelling events shifted between 24 and 48 h after the start of the Etesian wind. The upwelling always begins in the same areas of the Eastern Aegean coast with the only differences that these areas tesian wind pattern. The largest upwelling events occurred in summers 2003-2009 and not in the following years of the study period. The upwelled cold surface water, still pushed by the persistent Etesian wind, fills part of South-Eastern Aegean and eventually outflows the Aegean Sea through Kassos and Karpathos Straits of the eastern Cretan Arc.
Biogeochemical provinces are an important aid to identify homogeneous biogeochemical characteristics and underlying ecosystem dynamics in the open ocean. This macroscale approach, however, does not ...appear to be applicable to marginal seas for disregarding various small scale changes. Here, we adopted two observation schemes throughout the typical marginal seas, the South China Sea (SCS) and Straits of Malacca (MS), with continuous surface‐water sampling during March and May 2018. Spatial and seasonal heterogeneity of hydrological and dissolved organic matter (DOM) properties was investigated. With a novel combination of chromophoric DOM index and classical biogeochemical parameters (temperature, salinity, chlorophyll‐a, and bathymetry), we delineated five biogeochemical provinces in each season to integrate DOM pools and investigate region‐specific and season‐dependent biogeochemical processes. The results showed that the SCS basin was seasonally modulated by biological activities and photodegradation, resulting in the biologically active DOM pools. The western SCS seasonally received terrestrial DOM, subjected to the western boundary current under monsoon regulation. The MS was found to serve as an efficient carbon source of terrestrial substances, which exported to the northern Indian Ocean during the Northeast Monsoon. The delineation favored the simplification of complex biogeochemistry and allowed us to predict future trends in this dynamic system. Chromophoric DOM index was proven applicable to the delineation of marginal seas, that shed the light on the potential applications in biogeochemical provinces in dynamic systems.
Plain Language Summary
The concept of biogeochemical provinces has been put forward to identify distinct environmental conditions and to better interpret complex biogeochemical processes. Such approaches, however, have rarely been applied to the marginal seas, which are an ever‐changing seascape and provide global focal points. Assessment of oceanic dissolved organic matter (DOM) dynamics was the key building block for understanding the biogeochemical cycle. In our study, we depicted seasonal DOM dynamics in response to environmental forcing in the surface of the South China Sea and the Straits of Malacca, and incorporated the chromophoric DOM (CDOM) index to propose a biogeochemical province delineation in the study area. Our results highlight that the refined scheme of biogeochemical province delineation effectively interprets the complex biogeochemistry in marginal seas by incorporating CDOM index.
Key Points
The complexity of the South China Sea was emphasized with the spatially and seasonally heterogeneous dissolved organic matter (DOM) and biogeochemical forcing
The Straits of Malacca serve as an efficient source to export humic‐like terrestrial DOM to northern Indian Ocean during Northeast Monsoon
The refined biogeochemical province delineation scheme effectively interprets biogeochemistry in marginal seas by incorporating chromophoric DOM (CDOM) index
The pH of coastal seawater varies based on several local forcings, such as water circulation, terrestrial inputs, and biological processes, and these forcings are changing along with global climate ...change. Understanding the mechanism of pH variation in each coastal area is thus important for a realistic future projection that considers changes in these forcings. From 2020 to 2021, we performed parallel year-round observations of pH and related ocean parameters at five stations around the Japanese coast (Miyako Bay, Shizugawa Bay, Kashiwazaki Coast, Hinase Archipelago, and Ohno Strait) to understand the characteristics of short-term pH variations and their forcings. Annual variability (∼ 1 standard deviation) of pH and aragonite saturation state (Ωar) were 0.05–0.09 and 0.25–0.29, respectively, for three areas with low anthropogenic pressures (Miyako Bay, Kashiwazaki Coast, and Shizugawa Bay), while it increased to 0.16–0.21 and 0.52–0.58, respectively, in two areas with medium anthropogenic pressures (Hinase Archipelago and Ohno Strait in Seto Inland Sea). Statistical assessment of temporal variability at various timescales revealed that most of the annual variabilities in both pH and Ωar were derived by short-term variation at a timescale of <10 d, rather than seasonal-scale variation. Our analyses further illustrated that most of the short-term pH variation was caused by biological processes, while both thermodynamic and biological processes equally contributed to the temporal variation in Ωar. The observed results showed that short-term acidification with Ωar < 1.5 occurred occasionally in Miyako and Shizugawa bays, while it occurred frequently in the Hinase Archipelago and Ohno Strait. Most of such short-term acidified events were related to short-term low-salinity events. Our analyses showed that the amplitude of short-term pH variation was linearly correlated with that of short-term salinity variation, and its regression coefficient at the time of high freshwater input was positively correlated with the nutrient concentration of the main river that flows into the coastal area.
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