Seasonal Ekman upwelling in the Southwest Sumba from INDESO Model

Southwest Sumba water is part of the Indonesian fisheries management region (WPP573). Marine fisheries resources are influenced by oceanographic phenomena such as an upwelling event. This study aims to describe characteristics of seasonal Ekman upwelling by analyzing oceanographic parameters from the validated INDESO model output (2008-2014). It shows that upwelling event in the study area occurs during the Southeast Monsoon period, which creates an Ekman drift of 0.26 Sv towards offshore. This transported water mass is then replaced by an upwelled vertical flow of sub-surface colder and nutrient-rich water at the velocity of the order of 10−4 m/s. Surface features of the upwelling event are seen from a minimum temperature (24.3 °C), sea level anomaly (0.34 m), but the maximum of chlorophyll-a (3.02 mg/m3). During this time, an uplifted isotherm of 25.5 °C is found from sub-surface to 10 m depth, but it is outcropped at the sea surface in the centre of upwelling area. Interestingly, during upwelling event, salinity stratification revealed an isohaline of 34.10 psu is much deeper at 40 m depth, and much fresher water mass from the Ombai Indonesian Throughflow water is dominant. Averaged temperature-based upwelling index between June-September is about 0.3 °C.

High Chlorophyll-a Areas along the Western Coast of South Sulawesi-Indonesia during the Rainy Season Revealed by Satellite Data

The southern coast of South Sulawesi-Indonesia is known as an upwelling area occurring during dry season, which peaks in August. This upwelling area is indicated by high chlorophyll-a (Chl-a) concentrations due to a strong easterly wind-induced upwelling. However, the investigation of Chl-a variability is less studied along the western coast of South Sulawesi. By taking advantages of remote sensing data of Chl-a, sea surface temperature, surface wind, and precipitation, the present study firstly shows that along the western coast of South Sulawesi, there are two areas, which have high primary productivity occurring during the rainy season. The first area is at 119.0° E–119.5° E; 3.5° S–4.0° S, while the second area is at 119.0° E–119.5° E; 3.5° S–4.0° S. The maximum primary productivity in the first (second) area occurs in April (January). The generating mechanism of the high primary productivity along the western coast of South Sulawesi is different from its southern coast. The presence of river runoff in these two areas may bring anthropogenic organic compounds during the peak of rainy season, resulting in increased Chl-a concentration.

A Schematic Model of Low Temperature and High Salinity Seawaters in Southern Java of the Indian Ocean during ENSO-IOD 2017

The semi-peRmanent jAva coasTal Upwelling that is known as RATU, it was named semi-permanent because upwelling does not occur every month of the year in Southern Java has been investigated by several international researchers. However, this study focused on investigating the horizontal distribution of upwelling areas, using the indicator of low temperature (max. ∼26°C) and high salinity (min. 34 PSU) seawater mass, in different depth layers. The datasets were obtained from HYCOM, with the wind daily as well as the monthly ONI, SOI ENSO, and DMI datasets obtained from ECMWF, NOAA, BoM Australia, and Jamstec, respectively. Furthermore, the horizontal propagation of the low temperature and high salinity in 2017 at depths of 0 m, 50 m, 75 m, 125 m, 150 m, and 300 m have been observed and modeled as schematics. According to the results, the probable upwelling area begins from 150/125 meters to 75/50 meters layer depth. In these layers, the horizontal propagation from the east monsoon (July) to the transition monsoon (October) dominantly begins from the east and moves westward. This shows the highest correlation between temperature/salinity and SOI occurred from August to October during La Nina, from a depth of 0 m to 100m. Similarly, for the ONI, low temperature and high salinity also occurred from the Normal phase to the La Nina phase. The correlation between temperature/salinity and IOD shows the probable upwelling season occurred during IOD (+) phase until a 100 m depth because salinity becomes more irregular with increasing ocean depth.

Mercury Accumulation in Marine Sediments – A Comparison of an Upwelling Area and Two Large River Mouths

Understanding marine mercury (Hg) biogeochemistry is crucial, as the consumption of Hg-enriched ocean fish is the most important pathway of Hg uptake in humans. Although ocean sediments are seen as the ultimate Hg sink, marine sediment studies on Hg accumulation are still rare. In this context, studying Hg behavior in the marine environment, especially in upwelling environments, is of particular interest due to its importance in these great upwelling regions for the global fishery. There are contradictory statements about the fate of Hg in upwelling regions. Some studies have suggested high biotic reduction of oxidized Hg and gaseous elemental mercury evasion to the atmosphere. More recent work has suggested that in upwelling regions, where productivity is high, evasion of gaseous elemental mercury is diminished due to scavenging and sedimentation of Hg by organic particles. In this study, we compared Hg concentrations and accumulation rates in the past ∼4,300 and 19,400 years derived from sediment cores collected in the Peruvian upwelling region (Peru Margin) and compared them with those of two other cores collected from the sediment fan of the Amazon and a core from the Congo Basin, which is influenced by both seasonal coastal upwelling and discharge from the river. Median Hg concentrations were higher at the Peru Margin (90.7 μg kg–1) and in the Congo Basin (93.4 μg kg–1) than in the Amazon Fan (35.8 μg kg–1). The average Hg accumulation rates in sediments from the Peru Margin (178 μg m–2 yr–1) were factors of ∼4 and ∼39 times higher than those from the Congo Basin (46.7 μg m–2 yr–1) and Amazon Fan (4.52 μg m–2 yr–1), respectively. Principal component analysis (PCA) of the geochemical data set reveals that Amazon Fan sediments are strongly influenced by the deposition of terrestrial material, which is of less importance in the Congo Basin and of minor importance in Peru Margin sediments. Accordingly, Hg export to sediments in upwelling areas largely surpasses that in fans of large rivers that drain large terrestrial catchments. The high Hg accumulation rates in the sediments from the upwelling area and the minor influence of terrestrial Hg fluxes there suggest that atmospheric-derived Hg in upwelling areas is effectively exported to the sediments through scavenging by organic particles.

Distribution of Chromophytic Phytoplankton in the Eddy-Induced Upwelling Region of the West Pacific Ocean Revealed Using rbcL Genes

Marine chromophytic phytoplankton are a diverse group of algae and contribute significantly to the total oceanic primary production. However, the spatial distribution of chromophytic phytoplankton is understudied in the West Pacific Ocean (WPO). In this study, we have investigated the community structure and spatial distribution of chromophytic phytoplankton using RuBisCO genes (Form ID rbcL). Our results showed that Haptophyceae, Pelagophyceae, Cyanophyceae, Xanthophyceae, and Bacillariophyceae were the dominant groups. Further, chromophytic phytoplankton can be distinguished between upwelling and non-upwelling zones of the WPO. Surface and 75 m depths of a non-upwelling area were dominated by Prochlorococcus strains, whereas chromophytic phytoplankton were homogenously distributed at the surface layer in the upwelling zone. Meanwhile, Pelagomonas-like sequences were dominant at DCM (75 m) and 150 m depths of the upwelling zone. Non-metric multidimensional scaling (NMDS) analysis did not differentiate between chromophytic phytoplankton in the upwelling and non-upwelling areas, however, it showed clear trends of them at different depths. Further, redundancy analysis (RDA) showed the influence of physicochemical parameters on the distribution of chromophytic phytoplankton. Along with phosphate (p < 0.01), temperature and other dissolved nutrients were important in driving community structure. The upwelling zone was impacted by a decrease in temperature, salinity, and re-supplement of nutrients, where Pelagomonas-like sequences outnumbered other chromophytic groups presented.

Analisis Pola Sebaran Area Upwelling di Selatan Indonesia Menggunakan Citra Modis Level 2

This research aimed to find out the pattern of spasio-temporal upwelling and its relation with El Nino Southern Oscillation (ENSO) in the southern waters of Java to the East Nusa Tenggara. Two indicators namely sea surface temperature (SST) and chlorofil-a data obtained from oceancolor database were used as an indicator of upwelling occurences. The overlay technique and correlation analyses were used to describe the relationship between upwelling and ENSO. The results showed the phenomenon of upwelling occurred along southern Java and East Nusa Tenggara. The appearance of upwelling occurred in the South Easth Monsoon until transition season which began in June and ended in November. The pattern of upwelling area for 17 years varies each season, where for the South Easth Monsoon in June it gained 6986 km2, in July 78294 km2, and in August 254212 km2. As for transition season II in September 166767 km2, in October 72033 km2, and November 1949 km2. The results also showed that upwelling intensity was influenced by ENSO indicated by correlation values that matched the correlation value between SST - ENSO was -0.78 and chlorophyll-a-ENSO was 0.98.