Oceanographic Variables Research Articles

Spread of the non-native anemone Anemonia alicemartinae Häussermann & Försterra, 2001 along the Humboldt-current large marine ecosystem: an ecological niche model approach.

The geographical expansion of invasive species depends mainly on its dispersal potential, and the abiotic and biotic factors affecting it. Knowing the invasive dynamic of non-native species, as well as its behavior at different natural or anthropogenic scenarios, is fundamental for planning conservation management policies and control plans. The invasive sea anemone Anemonia alicemartinae in habits from the north (18°S) to the south-central (36°S) coast of Chile and its distribution range has expanded by approximately 1,928 km in the last 50 years. Previous works have proposed that human-mediated southward transport associated with regional-scale maritime activities could explain its rapid spread. To evaluate this hypothesis, we used ecological niche models (ENM) to evaluate the potential colonization of the southernmost area of South America. Additionally, we conducted a post hoc analysis to evaluate the relationship between the prediction of the ENM and human activity measured as the number of landings of ships in ports. The models were built based on presence records of A. alicemartinae, and oceanographic variables. Results showed that sea surface salinity and annual sea surface temperature (variance) are the best predictor variables to explain the distribution of A. alicemartinae. There was a positive and significant relationship between the geographical distribution of the sea anemone predicted by the ENM and the number of landings, as a proxy of anthropogenic activity. The most susceptible areas to invasion were those that showed the highest variability in both oceanographic predictors. These areas included the Biobío region, Chiloé´s inland sea, Aysén, and Chacabuco regions, which together comprise two biogeographical provinces. These results sustain the proposed hypothesis and, overall, the results suggest that along with the characteristics of the life history of A. alicemartinae, oceanographic conditions and maritime transport as vector contribute to the southern range expansion of this invasive cryptogenic species in the Humboldt-current large marine ecosystem.

Quarterly variability of floating plastic debris in the marine protected area of the Menorca Channel (Spain)

Plastic pollution is widespread in all the oceans and seas, representing a significant threat to most of their ecosystems even in marine protected areas (MPAs). This study determines the floating plastic distribution in four different periods between 2014 and 2015 in the recently approved Menorca Channel MPA (Balearic Islands). Plastic debris were persistent during all sampling periods on the surface of the Channel, composed mainly by the microplastic sizes. Average particle abundances ranged from 138,293 items⋅km−2 in autumn to 347,793 items⋅km−2 during the spring, while weight densities varied from 458.15 g(DW)⋅km−2 in winter to 2016.67 g(DW)⋅km−2 in summer. Rigid plastics were the most frequent particles in all the periods analysed (from 89.40%-winter to 94.54%-spring). The high-resolution and particle distribution models corroborated that the oceanographic variability shapes different patterns of presence of plastics, and in particular the existence of areas with almost no plastics.

CO2-dependent carbon isotope fractionation in Archaea, Part II: The marine water column

Abstract Stable carbon isotope ratios of archaeal glycerol dibiphytanyl glycerol tetraether (GDGT) lipids have been proposed as a proxy to infer past changes in the carbon isotope composition (δ13C) of dissolved inorganic carbon (DIC). The premise for paleo-δ13CDIC reconstructions from GDGTs is based on observations of relatively constant δ13CGDGT values in recent depositional environments. Marine Thaumarchaeota, thought to be the dominant source of GDGTs to marine sediments, fix inorganic carbon using the 3-hydroxypropionate/4-hydroxybutyrate (3HP/4HB) pathway, which is specific to HCO3– as the substrate. Bicarbonate-dependent autotrophy has been the basis for predicting that the stable carbon isotopic composition of GDGTs (δ13CGDGT) should vary in parallel with water column δ13CDIC values, because HCO3– is by far the dominant fraction of DIC in modern seawater. However, this relationship has never been systematically tested. Here we examine the carbon isotopic composition of GDGTs from four water column profiles in the Southwest and Equatorial Atlantic Ocean. Values of δ13CGDGT increase with depth in the water column, in contrast to the characteristic decrease in δ13CDIC values. These divergent trends imply a decrease in the observed total biosynthetic isotope effect (eAr) with depth, i.e., the offset between δ13CDIC and δ13CGDGT is not constant. Instead, we find that values of eAr specifically correlate with oceanographic variables associated with extent of organic remineralization, decreasing as CO2 concentration increases. This observed relationship is consistent in both magnitude and direction with the results of an isotope flux-balance model for Thaumarchaeota that suggests eAr should be sensitive to growth rate (μ) and CO2 availability under conditions of atmospheric pCO2

Behavioral response of a mobile marine predator to environmental variables differs across ecoregions

Animal movement and habitat selection are in part a response to landscape heterogeneity. Many studies of movement and habitat selection necessarily use environmental covariates that are readily available over large‐scales, which are assumed representative of functional habitat features such as resource availability. For widely distributed species, response to such covariates may not be consistent across ecosystems, as response to any specific covariate is driven by its biological relevance within the context of each ecosystem. Thus, the study of any widely distributed species within a limited geographic region may provide inferences that are not widely generalizable. Our goal was to evaluate the response of a marine predator to a suite of environmental covariates across a wide ecological gradient. We identified two behavioral states (resident and transient) in the movements of shortfin mako sharks Isurus oxyrinchus tracked via satellite telemetry in two regions of the western North Atlantic Ocean: the tropical Caribbean/Gulf of Mexico marginal sea (CGM), and the temperate waters of the open western Atlantic Ocean (OWA). We compared patterns of resident behavior between regions, and modeled relationships between oceanographic variables and resident behavior. We tracked 39 sharks during 2013–2015. Resident behavior was associated with shallow, continental shelf and slope waters in both regions. In the OWA resident behavior was associated with low sea surface temperature and high primary productivity, however, sharks exhibited no response to either variable in the CGM. There was a negative relationship between sea‐surface height gradient (a proxy for oceanic fronts) and resident behavior in the OWA, and a positive relationship in the CGM. Our observations likely reflect shark responses to regional variability in factors responsible for the distribution and availability of prey. Our study illustrates the importance of studying widely distributed species in a consistent manner over large spatial scales.

A hybrid CNN-LSTM model for typhoon formation forecasting

A typhoon is an extreme weather event that can cause huge loss of life and economic damage in coastal areas and beyond. As a consequence, the search for more accurate predictive models of typhoon formation; and, intensity have become imperative as meteorologists, governments, and other agencies seek to mitigate the impact of these catastrophic events. While work in this field has progressed diligently, this paper argues, that the existing models are deficient. Traditional numerical forecast models based on fluid mechanics have difficulty in predicting the intensity of typhoons. Forecasts based on statistics and machine learning fail to take into account the spatial and temporal relationships among typhoon formation variables leading to weaknesses in the predictive power of this model. Therefore, we propose a hybrid model, which we argue, can produce a more realist and accurate account of typhoon ‘behavior’ as it focuses on both the spatio-temporal correlations of atmospheric and oceanographic variables. Our CNN-LSTM model introduces 3D convolutional neural networks (3DCNN) and 2D convolutional neural networks (2DCNN) as a method to better understand the spatial relationships of the features of typhoon formation. We also use LSTM to examine the temporal sequence of relations in typhoon progression. Extensive experiments based on three datasets show that our hybrid CNN-LSTM model is superior to existing methods, including numerical forecast models used by many official organizations; and, statistical forecast and machine learning based methods.

Influence of shelf oceanographic variability on alternate foraging strategies in long-nosed fur seals

Central place foragers often change their foraging behaviour in response to changes in prey availability in the environment. Lactating long-nosed fur seals Arctocephalus forsteri (LNFS) at Cape Gantheaume in South Australia have been observed to display alternate foraging strategies, whereby they forage on the shelf in summer and switch to oceanic foraging in winter. We investigated the relationship between changes in shelf summertime upwelling and the timing and variability when females switch from predominantly shelf to oceanic foraging. Geolocation tags were deployed on females from summer to winter in 2016 and 2017, giving us longitudinal tracks over the transition period. The timing of switching from shelf to oceanic foraging was primarily driven by seasonal oceanographic changes on the shelf—specifically when the strength of the seasonal localised upwelling began to decline. The individual variability in the timing of the switch was driven by the strength of the coastal upwelling, with variability being greater in years when upwelling strength was weaker. By comparing our results to those of previous studies on the same colony, we found qualitative evidence that inter-annual environmental variability likely influences whether individuals display a single or multiple foraging strategies. This further highlights the flexibility in foraging strategies used by LNFS in response to environmental changes. The effect of inter-annual differences in foraging strategies on overall reproductive success warrants further investigation.

THE EFFECT OF OCEANOGRAPHIC FACTORS ON SKIPJACK TUNA FAD VS FREE SCHOOL CATCH IN THE BONE BAY, INDONESIA: AN IMPORTANT STEP TOWARD FISHING MANAGEMENT

The aims of this study were to compare skipjack catch between FAD and free school fishing grounds and to describe the effect of the oceanographic factors on either skipjack tuna Fish Aggregating Device (FAD) or free school. We used a field survey method for collecting the skipjack catch and the fishing positions for both near FAD and free school areas. Remotely sensed satellite data of sea surface temperature (SST) and chlorophyll-a concentration (Chl-a) were also used to extract the oceanographic data corresponding with both the fishing locations. To find out the vital oceanographic factors, we examined the characteristics of the oceanographic variables and skipjack catch using t-test. Results indicated that the fishing operations of skipjack tuna at FAD tended to locate areas of relatively higher Chl-a than at free school locations. We also found that skipjack tuna catch was higher near the FAD than the other area, where the Chl-a was the most significant factor that affected the difference. This study suggests that the number of skipjack tuna FAD in the coastal waters of Bone Bay should be calculated accurately to ensure and support the tuna fishing management in that study area.

Changes in the plankton community according to oceanographic variability in a shallow subtropical shelf: SW Atlantic

Copepods play a key role in marine ecosystems, acting as major primary consumers grazing on phytoplankton or feeding on microzooplankton. Plankton communities are mostly structured by nutrient availability and water temperature. The Subtropical Southwestern Atlantic Shelf has oligotrophic conditions due to the predominance of the Tropical Water in the upper layers. Its condition can change due to cold water upwelling in summer, the northwards spreading of the Plata Plume Water in winter, and local freshwater discharges. This study aimed to investigate the temporal and spatial variability in plankton community in the shallow shelf off the Brazilian coast (~ 27°S to 48°W). Results of the PERMANOVA analysis and co-occurrence networks revealed distinct seasonal communities. During winter the water was homogeneous, which supported the even distribution of the dominant species and the prevalence of the herbivore food chain throughout the area. During summer the herbivore food chain occurred in the bay area, being displaced by the microbial food chain toward the shelf. The plankton community is determined by the homogeneity of the water during winter and by the environmental heterogeneity during summer.

Predicting fisheries bycatch: A case study and field test for pilot whales in a pelagic longline fishery

AbstractAimFisheries bycatch is a major threat to populations of protected species such as marine mammals, seabirds and sea turtles, and static management approaches are often unsuccessful in mitigating bycatch of these highly mobile species. Combining species distribution models (SDMs) with oceanographic data has been proposed as a means of predicting when and where bycatch is likely to occur. However, studies assessing whether SDMs can accurately predict fisheries bycatch using independent data are lacking. Assessing model performance using independent data is necessary to test whether a model is generalizable, and this is particularly important for models with management applications. Here, we use short‐finned pilot whale (Globicephala macrorhynchus) bycatch in a pelagic longline fishery as a case study to inform efforts to mitigate fisheries bycatch.LocationOffshore waters, north‐east United States.MethodsWe integrated telemetry and oceanographic data using mixed‐effects generalized additive models to predict pilot whale occurrence and assessed model performance using k‐folds cross‐validation. We then evaluated the model's ability to predict pilot whale bycatch using data from independent on‐board observers.ResultsThe model performed well, and predictions were strongly and significantly correlated with observed rates of bycatch in space and time. Temperature and proximity to mesoscale oceanographic features (thermal fronts and sea level anomalies) were important predictors of pilot whale occurrence, and as a result, spatial predictions of the risk of bycatch varied through time.Main conclusionsOur findings demonstrate that SDMs can be used to accurately predict times and places with a high risk of bycatch, and illustrate that models using dynamic oceanographic variables can identify smaller, more specific focal management regions than static management approaches. Combining SDMs with near real‐time or forecasted environmental conditions could provide a promising tool for decreasing bycatch and will be valuable in developing adaptive management strategies to mitigate fisheries bycatch of protected species.

Anti submarine Warfare Oceanography

Anti-submarine warfare (ASW) Oceanography has become an important and independent discipline, especially after World War II as the threat perceptions from hostile underwater platforms has been on a continuously rising trajectory worldwide. There is no doubt that till date, acoustic energy remains the only viable and most effective means to detect underwater objects. However, sound waves are highly susceptible to refraction, reflection, scattering, reverberation and absorption in the ocean medium. Among these, refraction is controlled by the 3D sound speed structure in the specific ocean region and reflection loss by the sea state and ocean bottom characteristics. Water quality parameters such as sediment concentration and suspended biological masses influence attenuation, scattering, reverberation and absorption. Oceanographic variability emerges from diurnal heating, seasonal changes, river discharges, etc. and are the most important environmental factors deciding the 3D sound speed structure in any given area in the ocean.

Impact of deep-ocean eddies and fronts on the shelf seas of a sub-Antarctic Archipelago: The Prince Edward Islands

Abstract Ecosystems within the Southern Ocean, such as the Prince Edward Islands (PEIs), fulfil a pivotal role in sustaining rich environments with large populations of top predators. Many of these have already undergone dramatic shifts in response to changes in climate, highlighting the crucial need to enhance our understanding of drivers of oceanographic variability in the region, as well as their impacts on biological communities. Daily averaged bottom temperatures and water-column current speeds from two moorings in the inter-island region, between April 2014 and April 2018, present the first continuous set of high temporal resolution in situ measurements at the PEIs. These data were investigated to determine the influence of passing deep-sea mesoscale eddies and fronts on hydrographic conditions on the inter-island shelf. Warming/cooling events of the order of 0.5–2 °C, sometimes lasting longer than 30 days at a time, concomitant with changes in current speed and direction were associated with advection of waters into the shelf region from passing anticyclonic/cyclonic eddies. Similarly, the impact of frontal movement was quantified by increased current speeds throughout the water column when the southern branch of the sub-Antarctic Front (S-SAF), or the northern branch of the Antarctic Polar Front was in close proximity to the islands. When the S-SAF was located north of the PEIs, bottom temperatures were overall lower due to the stronger influx of Antarctic surface and intermediate waters. In contrast, when the S-SAF was close to or south of the PEIs, bottom temperatures were elevated as a result of the occurrence of larger proportions of warmer, more saline surface and intermediate sub-Antarctic and even Subtropical waters. Notably, the predominance of westerly flow in the southern portion of inter-island region suggested the perpetual existence of a Taylor column which was at times enhanced by the juxtaposition of some eddies.

From data compilation to model validation: a comprehensive analysis of a full deep-sea ecosystem model of the Chatham Rise

The Chatham Rise is a highly productive deep-sea ecosystem that supports numerous substantial commercial fisheries, and is a likely candidate for an ecosystem based approach to fisheries management in New Zealand. We present the first end-to-end ecosystem model of the Chatham Rise, which is also to the best of our knowledge, the first end-to-end ecosystem model of any deep-sea ecosystem. We describe the process of data compilation through to model validation and analyse the importance of knowledge gaps with respect to model dynamics and results. The model produces very similar results to fisheries stock assessment models for key fisheries species, and the population dynamics and system interactions are realistic. Confidence intervals based on bootstrapping oceanographic variables are produced. The model components that have knowledge gaps and are most likely to influence model results were oceanographic variables, and the aggregate species groups ‘seabird’ and ‘cetacean other’. We recommend applications of the model, such as forecasting biomasses under various fishing regimes, include alternatives that vary these components.

Oceanography of Harmful Algal Blooms on the Ecuadorian Coast (1997–2017): Integrating Remote Sensing and Biological Data

Ocean climate drivers and phytoplankton life strategies interact in a complex dynamic to produce harmful algal blooms (HABs). This study aims to integrate historical biological data collected during “red tide” events along the Ecuadorian coast between 1997 and 2017 in relation to five ocean variables derived from satellite remote sensing data to explain the seasonal drivers of coastal processes associated with HABs dynamics. Seasonality of the occurrence of HABs was assessed in relation to oceanographic variables by applying multiple correspondence analysis (MCA) to the Ecuadorian central coast (Zone 1) and at the outer and inner Gulf of Guayaquil (Zone 2). Sixty-seven HABs events were registered between 1997 and 2017. From a total of 40 species of phytoplankton identified, 28 were identified as non-toxic and the remaining 12 are well known to produce toxins. Dinoflagellates were the taxonomic group most highly associated with potential HABs events along the entire Ecuadorian coast. HABs appear to be constrained by the Humboldt coastal upwelling, high precipitation, and associated coastal runoff, with higher biomass abundance in the Gulf of Guayaquil than in the central coast. Results from the MCA reveal that in the central Ecuadorian coast (oligotrophic system), toxic HABs occurred with low abundance of dinoflagellates, while in the Gulf of Guayaquil (eutrophic system), toxic HABs corresponded to a high abundance of dinoflagellates. In both cases, high values were found for sea surface temperature, precipitation, and irradiance—characteristic of wet seasons or El Nino years. Non-toxic HABs occurred with a high abundance of dinoflagellates, ciliates, and centric diatoms, corresponding to colder waters and low levels of precipitation and irradiance. These findings confirm that dinoflagellates display several strategies that enhance their productive capacity when ocean conditions are warmer, allowing them to produce toxins at high or at low concentrations. Considering that the Gulf of Guayaquil is essential to tourism, the shrimp industry, fisheries, and international shipping, these findings strongly suggest the need to establish an ecosystem health research program to monitor HABs and the development of a preventive policy for tourism and public health in Ecuador.

Glacial differences of Southern Ocean Intermediate Waters in the Central South Pacific

Southern Ocean Intermediate Waters (SOIWs), such as Antarctic Intermediate Water and Subantarctic Mode Water, play a key role in modulating the global climate on glacial-interglacial time scales. They link the Southern Ocean and the tropics via mechanisms such as “oceanic tunneling” that transport climatic signals across latitudes. Despite their importance, the past evolution of the SOIWs in the Central South Pacific is largely unknown. Here we compare paired Mg/Ca-temperature, stable carbon (δ13C) and oxygen (δ18O) isotope records from surface-dwelling and deep-dwelling planktic foraminifera to infer changes in the water column structure for the last 260 ka in the Central South Pacific (54° S). Our study focuses on the subsurface oceanographic variability controlled by SOIWs, which are subducted at the Subantarctic Front.Our data show that the subsurface ocean in the Central South Pacific was colder and fresher during glacial stages than during the Holocene (0–10 ka BP), suggesting a general glacial enhanced presence of Antarctic Intermediate Water, in agreement with previous studies from the Eastern Equatorial Pacific and the Southeast Pacific. However, the subsurface ocean salinity differs for both glacial stages, with fresher condition during the Last Glacial Maximum (LGM; ∼26.5–19 ka BP) and more saline condition during the Penultimate Glacial Maximum (PGM; ∼155–140 ka BP). The δ13C data also show contrasting conditions for both glacial time windows in the upper water column, with a large depletion of 0.37‰ in δ13C from the LGM values, suggests a larger contribution of “old” low δ13C deep waters at intermediate depths at the study site during the PGM, plausibly due to stronger upwelling in high southern latitudes. The dissimilar scenarios between the LGM and the PGM may have been caused by processes that are analogous to the phase-switch in modern day Southern Annular Mode.

Dominant scales of subtidal variability in coastal hydrography of the Northern Chilean Patagonia

Abstract The Chilean Patagonia, on the southeastern Pacific Ocean, is one of the largest fjord systems in the world. Its complex topography harbors an aquaculture industry that is among the top exporters of salmon and mussels worldwide. However, little is known about the scales of environmental variability of this region and how climate-related changes can alter the current conditions. This study provides a baseline understanding of the dominant scales of subtidal variability in meteorological forcing and water properties along and across the region that encompasses northern Patagonia and specifically the Inner Sea of Chiloe (ISC). We examined multiple datasets spanning multiple spatial and temporal scales. Reanalysis wind time series were combined with satellite-derived data (MODIS-Aqua) and in situ hydrographic records from the mussel farming industry as well as from instruments moored at various locations in the ISC. We assessed the influence of large-scale forcing on the variability of local conditions and used the assembled datasets to find modes of variability at interannual, seasonal and intraseasonal scales. The patterns of atmospheric and oceanographic variability along northern Patagonia are heterogeneous both in time and space. Long-term sea surface temperature (SST) averages revealed two areas with colder temperatures and attenuated seasonal variability that can be associated with stronger vertical mixing. These areas have been previously related to hotspots for whale sightings and might be important as bottom-up controls of Patagonian food webs. Northern Patagonia is strongly affected by large-scale processes at the South Pacific basin scale. Long-term wind data show a poleward displacement of the transition between upwelling and downwelling favorable conditions during spring-summer months for the last decade. The intraseasonal time scale was dominated by a band centered at 30 days that can be attributed to atmospheric variability driven by the Baroclinic Annular Mode (BAM), which induces the periodic mixing of the water column, but with substantial interannual variability. Variability in local conditions was found to closely track the large-scale variability, even in the small channels and bays. These findings highlight the strong connection between large-scale processes and the conditions faced by aquaculture in the ISC, and the need to consider such scales of variability - as well as climate trends - in planning and management decisions.

Coastal oceanographic signatures of heat waves and extreme events of dense water formation during the period 2002-2012 (Barcelona, NW Mediterranean)

In a global context of climate change affecting the marine environment, it is important to consider the effect of extreme events in driving ecological change and to gain a better understanding of conditions to be expected under future scenarios. In this study we focus on monthly oceanographic data collected off Barcelona city during the period 2002-2012, in which extreme air temperatures and exceptional oceanographic events were reported in the western Mediterranean basin. These included two extreme heat waves and major episodes of dense water formation that produced unusually large deep-water contributions, induced oceanographic changes in the coastal zone and caused significant alterations to the marine ecosystem. To determine whether routine monitoring of oceanographic variables in a coastal zone can provide information for recognizing such large-scale events, temperature, salinity, turbidity and fluorescence were analysed to identify their signatures. The results provide an additional tool for monitoring oceanographic events and improving forecasts and future projections.

Foraging habitat choice of White-tailed Tropicbirds revealed by fine-scale GPS tracking and remote sensing.

BackgroundThe introduction of animal tracking technology has rapidly advanced our understanding of seabird foraging ecology. Tracking data is particularly powerful when combined with oceanographic information derived from satellite remote sensing, allowing insights into the functional mechanisms of marine ecosystems. While this framework has been used extensively over the last two decades, there are still vast ocean regions and many seabird species for which information is scarce, particularly in tropical oceans.MethodsIn this study we tracked the movement at high GPS recording frequency of 15 White-tailed Tropicbirds (Phaethon lepturus) during chick-rearing from a colony in Fernando de Noronha (offshore of Northeast Brazil). Flight behaviours of travelling and searching for food were derived from GPS data and examined in relation to satellite-sensed oceanographic variables (sea surface temperature, turbidity and chlorophyll-a concentration).ResultsWhite-tailed Tropicbirds showed marked preference for clear and warm sea surface waters, which are indicative of low primary productivity but are likely the best habitat for preying upon flying fish.DiscussionThese findings are consistent with previous studies showing that foraging habitat choices of tropical seabirds may not be driven by primary productivity, as has been widely shown for non-tropical species.

Large-Scale Spatial and Temporal Variability of Larval Fish Assemblages in the Tropical Atlantic Ocean.

This study investigated the large-scale spatial and temporal variability of larval fish assemblages in the west tropical Atlantic Ocean. The sampling was performed during four expeditions. Identification resulted in 100 taxa (64 families, 19 orders and 17 suborders). During the four periods, 80% of the total larvae taken represented eight characteristics families (Scombridae, Carangidae, Paralepididae, Bothidae, Gonostomatidae, Scaridae, Gobiidae and Myctophidae). Fish larvae showed a rather heterogeneous distribution with density at each station ranging from 0.5 to 2000 larvae per 100m3. A general trend was observed, lower densities at oceanic area and higher densities in the seamounts and islands. A gradient in temperature, salinity, phytoplankton biomass, zooplankton biomass and station depth was strongly correlated with changes in ichthyoplankton structure. Myctophidae, and Paralepididae presented increased abundance at high salinities and temperatures. Bothidae and Gobiidae were more abundant at higher phytoplankton biomass and zooplankton biomass. Scaridae, Scombridae and Gonostomatidae had higher abundances at deep offshore stations. Different events might be responsible for the formation, maintenance and breakdown of fish larvae assemblage in the tropical oceanic area of Brazil. The results suggested that the oceanographic variables (temperature, salinity, phytoplankton biomass, zooplankton biomass and station depth) played an important role on the distribution patterns of ichthyoplankton.

PROCESSING OCEANOGRAPHIC DATA BY PYTHON LIBRARIES NUMPY, SCIPY AND PANDAS

The study area is located in western Pacific Ocean, Mariana Trench. The aim of the data analysis is to analyze the potential influence of how various geological and tectonic factors may affect the geomorphological shape of the Mariana Trench. Statistical analysis of the data set in marine geology and oceanography requires an adequate strategy on big data processing. In this context, current research proposes a combination of the Python-based methodology that couples GIS geospatial data analysis. The Quantum GIS part of the methodology produces an optimized representative sampling dataset consisting of 25 cross-section profiles having in total 12,590 bathymetric observation points. The sampling of the geospatial dataset are located across the Mariana Trench. The second part of the methodology consists of statistical data processing by means of high-level programming language Python. Current research uses libraries Pandas, NumPy and SciPy. The data processing also involves the subsampling of two auxiliary masked data frames from the initial large data set that only consists of the target variables: sediment thickness, slope angle degrees and bathymetric observation points across four tectonic plates: Pacific, Philippine, Mariana, and Caroline. Finally, the data were analyzed by several approaches: 1) Kernel Density Estimation (KDE) for analysis of the probability of data distribution; 2) stacked area chart for visualization of the data range across various segments of the trench; 3) spacial series of radar charts; 4) stacked bar plots showing the data distribution by tectonic plates; 5) stacked bar charts for correlation of sediment thickness by profiles, versus distance from the igneous volcanic areas; 6) circular pie plots visualizing data distribution by 25 profiles; 7) scatterplot matrices for correlation analysis between marine geologic variables. The results presented a distinct correlation between the geologic, tectonic and oceanographic variables. Six Python codes are provided in full for repeatability of this research.

PREDICTING DUNE EROSION WITH COMBINED PROCESS-BASED AND MULTIVARIATE STATISTICAL MODELS

Oceanographic variables such as mean sea level, tides, storm surges, and waves are drivers of erosion, and they act on different time scales ranging from hours (associated with weather) to seasonal and decadal variations and trends (associated with climate). Storm erosion of dunes, which often protect coastal communities and built infrastructure from flooding, poses a major risk. Dune erosion is also a challenge to analyze and predict, due to the complex processes involved and the computational costs that come with it. Here, we introduce a novel framework that combines advanced statistical techniques and a process-based numerical model to efficiently simulate storm-induced dune erosion.