Open Pacific Ocean Research Articles

Early signals of El Niño 2023 in the Gulf of California?

After a long La Niña event (2020-2023), the US National Oceanographic and Atmospheric Administration warned of a quick transition to an El Niño phase. As a monitoring of sea surface temperature (SST) and chlorophyll-a (Chl-a) levels in the Gulf of California, Mexico, this study aims to show the evolution of both parameters during the first seven months of 2023. It compares them with the first seven months of 2015 when an extreme El Niño event occurred. Satellite data from the Moderate Resolution Imaging Spectroradiometer were obtained from which maps of both variables were constructed to quantitatively assess the changes in the SST and the Chl-a levels during the selected periods. Satellite data/pixels were extracted from the southern region of the gulf, in the connection between the gulf and the open Pacific Ocean. The results showed a gradual increase in the SST values from February to July of 2023 with 20.43, 22.29, 22.77, 27.88, 28.72 and 31.64ºC, respectively (a thermal variation of 11.21ºC), while Chl-a levels showed a decrease over the same period, from 1.81, 1.10, 0.78, 0.24, 0.19 mg m-3 to unusually low values of 0.11 mg m-3, respectively (a reduction of 1.70 mg m-3). A similar pattern was found in 2015, with increased SST and decreased Chl-a. Were the observed patterns in 2023 the early signals of El Niño in the Gulf of California?

Crustal architecture and tectonic development of western Queensland, Australia, based on deep seismic reflection profiling: Implications for Proterozoic continental assembly and dispersal

Interpretation of 2014–2015 deep crustal seismic reflection and magnetotelluric data has revised the architecture and geodynamic framework of western Queensland, with implications for the assembly and dispersal of the supercontinents Nuna, Rodinia and Gondwana. In the Mount Isa Province, crustal-scale boundaries of the Leichhardt River Domain, Kalkadoon-Leichhardt Domain and Eastern Subprovince are mapped in the third dimension. The Leichhardt River and Kalkadoon-Leichhardt domains have similar Nd isotopic T2DM model ages to provinces to the west, indicating they were part of ancestral North Australian Craton (NAC); the Eastern Subprovince is a separate terrane, with the Pilgrim Fault a collisional suture. The Gidyea Suture Zone separates the Mount Isa Province from the subsurface Numil Seismic Province. To the east, the west-dipping Yappar Fault separates east-dipping structures in the west from west-dipping structures in the east, forming a classic doubly vergent orogen within the upper plate of a convergent margin. The northwestern boundary of the Bernfels Seismic Province, the Kynuna Fault, truncates the Gidyea Suture Zone, implying this seismic province was welded to the NAC prior to initial deposition of the Etheridge Province. The Cork Fault truncates the north-south grain of the Mount Isa Province; the easternmost part of the NAC has been excised, presumably during breakup of Nuna. The subsurface Brighton Downs Seismic Province, formerly part of the northern Thomson Orogen, is a discrete seismic province, located between the NAC and the Thomson Orogen, and welded to the NAC during the accretion of Rodinia. Basement to the Thomson Orogen is a collage of microplates, accreted to the Brighton Downs Seismic Province during the assembly of Gondwana. By 530 Ma, eastern Australia faced an open Pacific Ocean, with the Thomson Orogen in a backarc setting. Thus, northeastern Australia contains a record of repeated continental accretion and breakup over at least three supercontinent cycles.

Tracking deep-sea internal wave propagation with a differential pressure gauge array

Temperature is used to trace ocean density variations, and reveals internal waves and turbulent motions in the deep ocean, called ‘internal motions.’ Ambient temperature detected by geophysical differential pressure gauges (DPGs) may provide year-long, complementary observations. Here, we use data from four DPGs fixed on the ocean bottom and a high-resolution temperature sensor (T-sensor) 13 m above the seafloor as a square-kilometer array deployed offshore ~ 50 km east of Taiwan facing the open Pacific Ocean to examine the impact of temperature on DPG signals related to internal motions. The DPG signals correlate with T-sensor temperature variations between 0.002 and 0.1 mHz, but have time shifts partially caused by slow thermal conduction from the ambient seafloor to the DPG chamber and partially by internal motion propagation time across the array. Applying beamforming-frequency-wavenumber analysis and linear regression to the arrayed T-sensor and DPG data, we estimate the propagating slowness of the internal motions to be between 0.5 and 7.4 s m−1 from the northwest and northeast quadrants of the array. The thermal relaxation time of the DPGs is within 103–104 s. This work shows that a systematic scan of DPG data at frequencies < 0.1 mHz may help shed light on patterns of internal wave propagation in the deep ocean, especially in multi-scale arrays.

Upper Pleistocene and Holocene Storm Deposits Eroded from the Granodiorite Coast on Isla San Diego (Baja California Sur, Mexico)

This project examines the role of hurricane-strength events likely to have exceeded 119 km/h in wind speed that entered the Gulf of California from the open Pacific Ocean during Late Pleistocene and Holocene times to impact the granodiorite shoreline on Isla San Diego. Conglomerate dominated by large, ellipsoidal to subspherical boulders at the islands south end were canvassed at six stations. A total of 200 individual cobbles and boulders were systematically measured in three dimensions, providing the database for analyses of variations in clast shape and size. The project’s goal was to apply mathematical equations elaborated after Nott (2003) with subsequent refinements to estimate individual wave heights necessary to lift igneous blocks from the joint-bound and exfoliated coast on Isla San Diego. On average, wave heights on the order of 3 m are calculated as having impacted the Late Pleistocene rocky coastline on Isla San Diego during storms, although the largest boulders more than a meter in diameter are estimated to weigh two metric tons and would have required waves in excess of 10 m for extraction. Described for the first time, a fossil marine biota associated with the boulder beds confirms a littoral-to-very-shallow water setting correlated with Marine Isotope Substage 5e approximately 125,000 years ago. A narrow submarine ridge consisting, in part, of loose cobbles and boulders extends for 1.4 km to the southwest from the island’s tip, suggesting that Holocene storms continued to transport rock debris removed from the shore. The historical record of events registered on the Saffir–Simpson Hurricane Wind Scale in the Gulf of California suggests that major storms with the same intensity struck the island in earlier times.

Stable Biological Production in the Eastern Equatorial Pacific Across the Plio‐Pleistocene Transition (∼3.35–2.0 Ma)

AbstractUpwelling within the Eastern Equatorial Pacific (EEP) Ocean is a key factor for the Earth's climate because it supports &gt;10% of the present‐day biological production. The dynamics of upwelling in the EEP across the Plio‐Pleistocene transition—an interval particularly relevant for understanding near‐future warming due to Anthropocene‐like atmospheric carbon‐dioxide levels—have been intensively studied for the region east of the East Pacific Rise. In contrast, changes of the equatorial upwelling regime in the open Pacific Ocean west of this oceanographic barrier have received markedly less attention. We therefore provide new proxy records from Ocean Drilling Program Site 849 located within the EEP open‐ocean upwelling regime. Our target interval (∼3.35–2.0 Ma) covers the Plio‐Pleistocene transition characterized by the intensification of Northern Hemisphere Glaciation (iNHG). We use benthic δ18O values to generate a new, high‐resolution age model for Site 849, and sand‐accumulation rates together with benthic δ13C values to evaluate net export production. Although showing temporary substantial glacial‐interglacial variations, our records indicate stability in net export production on secular timescales across the iNHG. We suggest the following processes to have controlled the long‐term evolution of primary productivity at Site 849. First, nutrient export from the high latitudes to the EEP; second, a successive shoaling of the Pacific nutricline during the studied interval; and third, a simultaneous reduction in dust‐borne iron input.

Air-water exchange and distribution pattern of organochlorine pesticides in the atmosphere and surface water of the open Pacific ocean

Surface seawater and lower atmosphere gas samples were collected simultaneously between 18°N and 40°S in the open Pacific Ocean in 2006–2007. Samples were analyzed for organochlorine pesticides (OCPs) to assess their distribution patterns, the role of ocean in the long-range transport (LRT), and the air-water exchange directions in the open Pacific Ocean. Such open ocean studies can yield useful information such as establishing temporal and spatial trends and assessing primary vs secondary emissions of legacy OCPs. Target compounds included hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs) and its derivatives, and chlordane compounds. Concentrations for α-HCH, γ-HCH, trans-chlordane (TC), and cis-chlordane (CC) were higher in the Northern Hemisphere (NH) than the Southern Hemisphere (SH) in both gaseous and dissolved phases, while the distribution patterns of DDTs and heptachlor exo-epoxide (HEPX) showed a reversed pattern. In the N Pacific, concentrations of α-HCH and γ-HCH in the present work were lower by 63 and 16 times than those observed in 1989–1990. The distribution patterns of DDT suggested there was usage in the SH around 2006. Calculated fugacity ratios suggested that γ-HCH was volatilizing from surface water to the atmosphere, and the air-water exchange fluxes were 0.3–11.1 ng m−2 day−1. This is the first field study that reported the open Pacific Ocean has become the secondary source for γ-HCH and implied that ocean could affect LRT of OCPs by supplying these compounds via air-sea exchange.

Wind stress over the Pacific Ocean east of Japan drives the shelf circulation east of China

In the western Pacific Ocean, the Kuroshio cross-shelf intrusion and the shelf circulation are vital components of the coastal environment. However, the key dynamic factors driving them remained unclear. Our model and theoretical analysis show that wind stress over the open Pacific Ocean east of Japan drives a net equatorward water flux of 2.2 Sv, and this flux sets up a south-north sea surface drop from the East China Sea (ECS) to the Japan Sea which drives a throughflow of 2.6 Sv poleward through the Tsushima Strait. This throughflow requires a shelf circulation in the ECS to balance the mass flux. Thus, the Kuroshio Current must intrude onto the ECS shelf and there must be a poleward flowing Taiwan Warm Current through Taiwan Strait. It is the wind stress over the Northeastern Pacific Ocean interior rather than the local wind that drives and regulate both the Kuroshio cross-shelf intrusion and the shelf circulation.

Population Genetic Structure at the Northern Edge of the Distribution of Alexandrium catenella in the Patagonian Fjords and Its Expansion Along the Open Pacific Ocean Coast

In southern Chile, Alexandrium catenella is the main species generating HABs and over time it has expanded its range since it was first recorded in the Magallanes region in 1972. In 2016 a severe bloom of an Alexandrium species occurred, which was notable for its intensity and geographical extent, extending into new areas to the north of the Patagonian fjords including areas along the open Pacific Ocean coast. Given the exceptional nature of this event, we verified the taxonomic classification of the species that generated the bloom and evaluated the influence of the range expansion process on its genetic structure and population diversity. This was achieved by isolating clones collected in 2014 from cyst beds located at the northern limit of its then known distribution, along with clones isolated from the water samples taken during the 2016 bloom. These clones were characterized genetically with LSU rDNA and AFLPs molecular markers. Phylogenetic analyses showed that all clones were aggregated in the Group I of the A. tamarense species complex, which confirmed that A. catenella was the species responsible for the 2016 bloom. High genetic diversity was observed within populations though there were no significant differences between populations. Furthermore, genetic structure showed an isolation by distance relationship among populations, and several analyses consistently indicated a high divergence among the population groups derived from both cysts and vegetative cells. Despite this study not finding the patterns expected for species range expansion (i.e. diversity gradient and/or high population divergence), the genetic diversity and structure indicated that these were influenced by the geographic distance effect and the physical restrictions to gene flow, along with the demographic processes that occurred during the distinct phases of the life cycle of A. catenella.

Japan and Taiwan – a Strategic Convergence?

&lt;p&gt;Artykuł dotyczy współzależności strategicznych Japonii i Tajwanu. Są one konsekwencją z jednej strony wzrostu Chin, z drugiej coraz większej militarnej aktywności Japonii w regionie. Tajwan chcąc ochronić swój obecny status potrzebuje zbudowania silnej koalicji w regonie. Zachowanie status quo Tajwanu leży również w interesie Japonii, ze względu na jego położenie geopolityczne. Tajwan pełni rolę bariery pomiędzy Chinami a otwartym Pacyfikiem, będąc częścią tzw. pierwszego łańcuch wysp. Zatem przejęcie Tajwanu przez Chiny miałoby katastrofalne skutki dla Japonii, oraz zachwiałoby poważnie równowagę w regionie Azji i Pacyfiku.&lt;/p&gt;

Distribution and abundance patterns of echinoderms in the fjord and channel complex from a subantarctic north Patagonian Ice field, Magellan region

The existence of latitudinal marine biodiversity gradients from low to high-southern latitudes is a controversial issue regarding the marine biogeographic division in the Southeastern Pacific. In this region, the Northern Patagonian Icefield is considered a break point for faunistic elements derived from more northern or southern biogeographical realms. However, the division seems to be better defined by distribution patterns and endemism of specific marine taxa. There have been no exhaustive latitudinal benthic inventories compiled along the southern-eastern Pacific Chilean coastline. This study focuses on the spatial distribution variability and relative abundance of the sublittoral echinoderm assemblages and uses them to establish an evaluation of zoogeographic relationship in the Southeastern Pacific and Atlantic Oceans. This is the first time echinoderms have been used for this purpose. A total 3 665 echinoderm specimens were collected in two cruises. Within this organism pool, 29 species were distinguished, belonging to the asteroids (17 species), echinoids (6 species), ophiuroids (4 species) and holothurians (2 species); crinoids were not found. The dominant species were the asteroid Ctenodiscus procurator, the echinoid Pseudechinus magellanicus, the ophiuroid Ophiuroglypha lymani, and the irregular sea urchin Tripylaster philippii. The spatial distribution patterns for the echinoderm clusters along the study area showed only weak geographical trends. Stations belong in three groups: with influence of glacier processes, influence of waters of the open Pacific Ocean, and a third group of stations without any links to specific locations. Rev. Biol. Trop. 65(Suppl. 1): S60-S72. Epub 2017 November 01.

Distribution and diffusion of surface suspended matter off the East China Shore, 2010

AbstractIt is a question whether the suspended sediment from the China continent could enter the Kuroshio Current and Pacific Ocean. Surface suspended matter (SSM) and sea surface temperature (SST) in the East China Seas from December 2009 to November 2010 has been extracted from the satellite NOAA‐19 AVHRR/3. We have monitored the change of the SSM diffusion during summer half‐year and winter half‐year. High SSM areas occur in the inshore of the Liaodong Bay, Bohai Bay, Yellow River Delta, Shandong Peninsula, Jiangsu Coast and Yangtze Estuary, especially blooming in winter half‐year. Going by our findings, the sediment provenance influences the SSM distribution, and the current system and monsoon are important factors that drive the SSM diffusion all year round. In winter half‐year, the ocean colour images show that the current system is well developed. The SSMs are transported southeastward, and a part reaching the outer continental shelf is captured by the Kuroshio Current before it finally reaches the open Pacific Ocean through the Tokara Strait. Some SSMs are transported by the Yellow Sea and Tsushima Warm Current into the Yellow Sea and Japan Sea. In summer half‐year, most of the SSM could not reach the continental shelf break and only little SSM could be captured by the Kuroshio Current into the open ocean. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Seasonal variation of atmospheric particulate mercury over the East China Sea, an outflow region of anthropogenic pollutants to the open Pacific Ocean

In this study, PM2.5 and total suspended particulate (TSP) aerosol samples were collected to investigate atmospheric mercury pollution on a pristine island in the East China Sea (ECS) from October 2011 to August 2012. The sampling site is located in the downwind path of the outflow of anthropogenic pollutants from East Asia to the Pacific Ocean, driven by the East Asian monsoon. Average concentrations of particulate mercury (PHg, in pg/m3) were 16.6 for PM2.5 and 24.2 for TSP. Particulate mercury was mainly present in the fine mode, with 68.5% of the total PHg being present in PM2.5. Obvious seasonal variations were observed for both PM2.5 and TSP. The dry deposition flux of PHg over the ECS was estimated to be 1.69 μg m−2 yr−1. Three episodes of high PHg concentrations were observed during the sampling period. An episode in fall (84.1 pg/m3 in TSP) was induced by biomass burning in East China, and PHg was more concentrated in the fine mode (PM2.5/TSP = 0.91). An episode in winter was triggered by serious anthropogenic emissions in northern China, with PHg levels reaching 132.7 pg/m3 in TSP. An episode in spring was attributed to the long-range transport of Asian dust mixed with anthropogenic aerosols, with increased levels of PHg in the coarse mode (PM2.5/TSP = 0.61). Principal component analysis (PCA) indicated that fossil fuel combustion and biomass burning from the Asian mainland were the two major sources of atmospheric PHg over the ECS.

Repeat Storm Surge Disasters of Typhoon Haiyan and Its 1897 Predecessor in the Philippines

AbstractOn 8 November 2013, Typhoon Haiyan impacted the Philippines with estimated winds of approximately 314 km h-1 and an associated 5–7-m-high storm surge that struck Tacloban City and the surrounding coast of the shallow, funnel-shaped San Pedro Bay. Typhoon Haiyan killed more than 6,000 people, superseding Tropical Storm Thelma of November 1991 as the deadliest typhoon in the Philippines. Globally, it was the deadliest tropical cyclone since Nargis hit Myanmar in 2008. Here, we use field measurements, eyewitness accounts, and video recordings to corroborate numerical simulations and to characterize the extremely high velocity flooding caused by the Typhoon Haiyan storm surge in both San Pedro Bay and on the more open Pacific Ocean coast. We then compare the surge heights from Typhoon Haiyan with historical records of an unnamed typhoon that took a similar path of destruction in October 1897 (Ty 1897) but which was less intense, smaller, and moved more slowly. The Haiyan surge was about twice the height of the 1897 event in San Pedro Bay, but the two storm surges had similar heights on the open Pacific coast. Until stronger prehistoric events are explored, these two storm surges serve as worst-case scenarios for this region. This study highlights that rare but disastrous events should be carefully evaluated in the context of enhancing community-based disaster risk awareness, planning, and response.

Dynamic changes in the composition of photosynthetic picoeukaryotes in the northwestern Pacific Ocean revealed by high-throughput tag sequencing of plastid 16S rRNA genes

Photosynthetic picoeukaryotes (PPEs) are major oceanic primary producers. However, the diversity of such communities remains poorly understood, especially in the northwestern (NW) Pacific. We investigated the abundance and diversity of PPEs, and recorded environmental variables, along a transect from the coast to the open Pacific Ocean. High-throughput tag sequencing (using the MiSeq system) revealed the diversity of plastid 16S rRNA genes. The dominant PPEs changed at the class level along the transect. Prymnesiophyceae were the only dominant PPEs in the warm pool of the NW Pacific, but Mamiellophyceae dominated in coastal waters of the East China Sea. Phylogenetically, most Prymnesiophyceae sequences could not be resolved at lower taxonomic levels because no close relatives have been cultured. Within the Mamiellophyceae, the genera Micromonas and Ostreococcus dominated in marginal coastal areas affected by open water, whereas Bathycoccus dominated in the lower euphotic depths of oligotrophic open waters. Cryptophyceae and Phaeocystis (of the Prymnesiophyceae) dominated in areas affected principally by coastal water. We also defined the biogeographical distributions of Chrysophyceae, prasinophytes, Bacillariophyceaea and Pelagophyceae. These distributions were influenced by temperature, salinity and chlorophyll a and nutrient concentrations.

Emission, Dynamics and Transport of Perfluoroalkyl Substances from Land to Ocean by the Great East Japan Earthquake in 2011.

Water samples collected along the Japanese coast and in the open Pacific Ocean in 2010, 2011, and 2012 were analyzed for perfluoroalkyl substances (PFASs) to evaluate the effect of Great East Japan Earthquake (EQ 3.11), which occurred on March 11, 2011, on the dispersion of chemical pollutants. Ultratrace analysis of PFASs in water, a super computer simulation, and an inventory analysis from industrial records revealed the sources and dynamics of PFASs during the EQ 3.11 disaster. In this respect, EQ 3.11 destroyed solid infrastructure on land, and within minutes, PFASs stocked therein were released into the open environment. The historically significant tsunami backwash swept them away from their origin to the coastal water within several hours. It was estimated that from 0.8 to 1.0 tons of perfluorooctanesulfonate (PFOS) and 4.8 to 5.1 tons of PFOA were discharged into the coastal waters after EQ 3.11 and the tsunami that followed. The reconstruction of EQ 3.11 also traced the influence of this pollution in open ocean water until March 2012, and a statistical and finger printing analysis revealed that there were different distribution mechanisms in coastal regions than in the open ocean for PFOS, other shorter chain perfluorinated sulfonic acids and perfluorinated carboxylic acids.

Fukushima radionuclides in the NW Pacific, and assessment of doses for Japanese and world population from ingestion of seafood.

Variations of Fukushima-derived radionuclides (90Sr, 134Cs and 137Cs) in seawater and biota offshore Fukushima and in the NW Pacific Ocean were investigated and radiation doses to the Japanese and world population from ingestion of seafood contaminated by Fukushima radionuclides were estimated and compared with those from other sources of anthropogenic and natural radionuclides. The total effective dose commitment from ingestion of radionuclides in fish, shellfish and seaweed caught in coastal waters off Fukushima was estimated to be 0.6 ± 0.4 mSv/y. The individual effective dose commitment from consumption of radioactive-contaminated fish caught in the open Pacific Ocean was estimated to be 0.07 ± 0.05 mSv/y. These doses are comparable or much lower than doses delivered from the consumption of natural 210Po in fish and in shellfish (0.7 mSv/y). The estimated individual doses have been below the levels when any health damage of the Japanese and world population could be expected.

Shipboard determination of radiocesium in seawater after the Fukushima accident: results from the 2011–2012 Russian expeditions to the Sea of Japan and western North Pacific Ocean

A total of 88 seawater samples were collected during two Russian research expeditions (April–May 2011 and August–September 2012) to the Sea of Japan, the Oyashio Current region near Kuril Islands and the Kuroshio–Oyashio transition area in the western North Pacific Ocean. The observations were made aboard the R/V Pavel Gordienko and Akademik Shokalsky in order to study the impact of the Fukushima accident on radioactive contamination of the marine environment. On the board of a ship, the water samples were passed through filters to retain particles with the size of >1 micron. Cesium was extracted from the large volumes (100–3000 L) of the filtrated water using a selective fiber chemisorbent impregnated with copper ferrocyanide. Measurements of 134Cs and 137Cs activities in 83 samples of sorbents and 21 samples of filters were performed in the ship-based laboratory with a semiconductor HP-Ge detector. The quantified activity concentrations of dissolved radiocesium ranged from 1 Bq m−3 to 34 Bq m−3 for 137Cs and from 0.2 Bq m−3 to 29 Bq m−3 for 134Cs. Activity concentrations of 137Cs and 134Cs were strongly correlated with each other (r = 0.993, n = 59). The 137Cs/134Cs activities ratio in the Fukushima-derived radiocesium inventory for the study areas was deduced to be 0.99 ± 0.03 (on 15 March 2011) and the pre-Fukushima background level of 137Cs in seawater was estimated as 1.3 ± 0.3 Bq m−3. The lowest activities of both isotopes were determined in the western part of the Sea of Japan near the Russian coast, while the maximal levels were observed in the open Pacific Ocean, some 500–800 km offshore the Fukushima Dai-ichi Nuclear Power Plant. Contamination with 134Cs at a level of 0.3–2.6 Bq m−3 was registered in seawater samples collected in 2011 near the Kuril Islands and Kamchatka in the Oyashio Current region. During the period from April–May 2011 to August–September 2012, activity concentrations of 137Cs and 134Cs in surface waters had decreased for all seven stations repeatedly sampled in the study. A detailed observation of radiocesium distribution within the water column down to the depth of 200 m at nine stations from the Kuroshio–Oyashio Interfrontal Zone and Kuroshio Extension in 2012 revealed maximal activity concentrations of both cesium radionuclides in the 100–200 m depth layer. The average inventory of Fukushima-derived 137Cs in the top 200 m of the water column for the nine stations was estimated as 1.19 kBq m−2 (decay corrected to 15 March 2011) which is 4.6 times higher than the background value of 0.26 kBq m−2 expected for this depth. The monitoring results obtained in the study and relevant data published by others show that following the Fukushima accident, the Oyashio current acts as a provider of low-contaminated subarctic waters to the heavily contaminated Kuroshio–Oyashio mixed water region.

Contribution of iceberg sounds to the ambient noise budget in the South Pacific Ocean

On May 2002, C19, a 5500 km2 iceberg calved from the Ross Ice Shelf, eventually drifting eastward into the open Pacific Ocean by 2008. As it sailed into warmer waters, thermal and wind stresses caused the iceberg to crack and break apart. These resulting “icequakes” projected wideband acoustic energy into the water column, influencing the regional ambient noise environment. Icequake noise was persistent and strong enough to be observed by NOAA’s eastern equatorial Pacific moored hydrophone (EEP-NW at 8N, 110W) as well as the hydroacoustic station of International Monitoring System (IMS) on Juan Fernandez Island (H03N at 33.44S, 78.91W). Elevated noise levels (maximum of ~+3 dB at NOAA’s EEP and ~+7 dB at IMS H03N hydrophones) were observed by both stations from early 2008 when C19a first appeared in the Pacific until it drifted into the Atlantic Ocean in early 2009. C19a’s icequake and calving activity was also most frequent during this same period. Seasonal changes and long-term trends in ambient noise levels at NOAA’s EEP-NW acoustic mooring (1996–2009) and IMS Juan Fernandez (2003–2010 years) and the unique acoustic role icebergs play in the Southern Ocean will be presented.

Dispersion of Fukushima radionuclides in the global atmosphere and the ocean

Large quantities of radionuclides were released in March–April 2011 during the accident of the Fukushima Dai-ichi Nuclear Power Plant to the atmosphere and the ocean. Atmospheric and marine modeling has been carried out to predict the dispersion of radionuclides worldwide, to compare the predicted and measured radionuclide concentrations, and to assess the impact of the accident on the environment. Atmospheric Lagrangian dispersion modeling was used to simulate the dispersion of 137Cs over America and Europe. Global ocean circulation model was applied to predict the dispersion of 137Cs in the Pacific Ocean. The measured and simulated 137Cs concentrations in atmospheric aerosols and in seawater are compared with global fallout and the Chernobyl accident, which represent the main sources of the pre-Fukushima radionuclide background in the environment. The radionuclide concentrations in the atmosphere have been negligible when compared with the Chernobyl levels. The maximum 137Cs concentration in surface waters of the open Pacific Ocean will be around 20Bq/m3. The plume will reach the US coast 4–5y after the accident, however, the levels will be below 3Bq/m3. All the North Pacific Ocean will be labeled with Fukushima 137Cs 10y after the accident with concentration bellow 1Bq/m3.

Annual record of particle fluxes, geochemistry and diatoms in Effingham Inlet, British Columbia, Canada, and the impact of the 1999 La Niña event

Sediment traps were deployed inside the anoxic inner basin of Effingham Inlet and at the oxygenated mouth of the inlet from May 1999 to September 2000 in a pilot study to determine the annual depositional cycle and impact of the 1999 La Niña event within a western Canadian inlet facing the open Pacific Ocean. Total mass flux, geochemical parameters (carbon, nitrogen, opal, major and minor element contents, and stable isotope ratios) and diatom assemblages were determined and compared with meteorological and oceanographic data. Deposition was seasonal, with coarser grained terrestrial components and benthic diatoms settling in the autumn and winter, coincident with the rainy season. Marine sedimentary components and abundant pelagic diatoms were coincident with coastal upwelling in the spring and summer. Despite the seasonal differences in deposition, the typical temperate-zone Thalassiosira – Skeletonema – Chaetoceros bloom succession was muted. A July 1999 total mass flux peak and an increase in biogenous components coincided with a rare bottom-water oxygen renewal event in the inlet. Likewise, there were cooler-than-average sea surface temperatures (SSTs) just outside the inlet, and unusually high abundances of a previously undescribed cool-water marine diatom ( Fragilariopsis pacifica sp. nov.) within the inlet. Each of these occurrences likely reflects a response to the strong La Niña that followed the year after the strongest-ever recorded El Niño event of 1997–1998. By the autumn of 1999, SSTs had returned to average, and F. pacifica had all but disappeared from the remaining trap record, indicating that oceanographic conditions had returned to normal. Oxygenation events were not witnessed in the inlet in the years before or after 1999, suggesting that a rare oceanographic and climatic event was captured by this sediment trap time series. The data from this record can therefore be used as a benchmark for identifying anomalous environmental conditions on this coast. ► Only sediment trap study done in a western Canadian inlet facing the open Pacific ► Deposition of settling particles is clearly seasonal. ► Deposition of settling particles is also influenced by the 1999 La Niña event. ► 1999 La Niña had a strong oceanographic and biological effect on the coast. ► Sediment trap data can be used as benchmarks recording anomalous climatic events.