Marine Fronts Research Articles

CO2 sink and source zones delimited by marine fronts in the Drake Passage

Net sea-air CO2 fluxes (FCO2) in the Drake Passage (DP) were studied at a climatological scale (1999–2019) using observations from the Surface Ocean CO2 Atlas (SOCAT) database. Based on the monthly climatological position of the main circumpolar fronts of the DP (the Subantarctic Front (SAF), the Polar Front (PF) and the Southern Antarctic Circumpolar Current Front (SACCF)) and the thermal and nonthermal contributions to FCO2, we present a regional subdivision into different regimes that provide new insights into the processes controlling these fluxes. Our results indicate that the region in the north of SAF (R1) behaves as an annual CO2 sink (-1.3 ± 1.0 mmol m−2 d−1); this sink weakens between SAF-PF (R2) and PF-SACCF (R3) and the region south of SACCF (R4) acts as an annual CO2 source (2.2 ± 3.3 mmol m−2 d−1). The annual mean CO2 uptake in DP is 1.3 ± 15.5 Tg C yr-1. Analysis of thermal (TE) and nonthermal (nonTE) effects on seasonal sea surface CO2 partial pressure (pCO2sw) variability indicates that DP is mainly dominated by nonTE. Results emphasize that carbon fluxes are driven by mesoscale and submesoscale processes north of the PF and by the upwelling of Upper Circumpolar Deep Waters in the Antarctic boundary of the DP, while seasonal patterns are mostly modulated by local factors such as nutrient availability, biological activity and ice cover.

Observational Studies of Ocean Fronts: A Systematic Review of Chinese-Language Literature

This review will serve as an entry point for international researchers who would like to tap into the vast scientific potential of Chinese-language literature on oceanic fronts. We focused on observational physical oceanography studies of marine fronts. A thorough bibliographic search netted 95 papers published in 1982–2023, with a sharp increase in the total number of papers from 2006–2010 to 2011–2015, when this number almost tripled. This trend continued unabated through the early 2020s. The sharp increase in Chinese-language publications preceded by several years a rapid increase in English-language publications in the same field. Regionally, the overwhelming majority of papers is focused on the China Seas, particularly the East China Seas and northern South China Sea. Elsewhere, a number of papers were dedicated to the Southern Ocean and North Atlantic. Thematically, papers on remote sensing of ocean fronts dominate the literature, with special attention to the development of front-detection algorithms that can be applied to satellite data on sea surface temperature, salinity, chlorophyll, and sea level anomaly. Numerous papers on marine fronts in the China Seas present important results that have to be considered by international researchers. Overall, this review emphasizes the significant contributions made by Chinese oceanographers, particularly to studies of the frontal oceanography of the China Seas.

Response of biological productivity to North Atlantic marine front migration during the Holocene

Abstract. Marine fronts delineate the boundary between distinct water masses and, through the advection of nutrients, are important facilitators of regional productivity and biodiversity. As the modern climate continues to change, the migration of frontal zones is evident, but a lack of information about their status prior to instrumental records hinders future projections. Here, we combine data from lipid biomarkers (archaeal isoprenoid glycerol dibiphytanyl glycerol tetraethers and algal highly branched isoprenoids) with planktic and benthic foraminifera assemblages to detail the biological response of the marine Arctic and polar front migrations on the North Iceland Shelf (NIS) over the last 8 kyr. This multi-proxy approach enables us to quantify the thermal structure relating to Arctic and polar front migration and test how this influences the corresponding changes in local pelagic productivity. Our data show that following an interval of Atlantic water influence, the Arctic front and its associated high pelagic productivity migrated southeastward to the NIS by ∼6.1 ka. Following a subsequent trend in regional cooling, Polar Water from the East Greenland Current and the associated polar front spread onto the NIS by ∼3.8 ka, greatly diminishing local algal productivity through the Little Ice Age. Within the last century, the Arctic and polar fronts have moved northward back to their current positions relative to the NIS and helped stimulate the productivity that partially supports Iceland's economy. Our Holocene records from the NIS provide analogues for how the current frontal configuration and the productivity that it supports may change as global temperatures continue to rise.

Larval transport of Aristeus antennatus shrimp (Crustacea: Decapoda: Dendrobranchiata: Aristeidae) near the Palamós submarine canyon (NW Mediterranean Sea) linked to the North Balearic Front

Marine fronts are oceanographic drivers for marine species dispersal, especially for their pelagic organisms like the larvae. Larvae can aggregate at the front and consequently have a limited dispersal, which in turn reduces the connectivity between marine populations. Due to the high variations in the ocean, the fronts also have annual changes (i.e., its formation period, gradient, and position), which have poorly-documented effects on larval retention. In the northwestern Mediterranean Sea, a surface density front is localized across a continental margin which is also indented by submarine canyons. There, an abundant population of the commercial deep-sea blue and red shrimp Aristeus antennatus (Crustacea: Decapoda: Dendrobranchiata: Aristeidae) inhabits the seafloor. Each summer, the shrimp offspring are released in pelagic deep-sea and access the superficial waters divided by the density front. In this study, we focused on the interannual variability of the density front influence on the larval transport of shrimps and its repercussions on the potential connectivity between shrimp populations at each front side. A particle-tracking model simulated the larval transport of A. antennatus in hydrodynamics of the northwestern Mediterranean Sea between the years 2006 and 2016. Larval drift distance and seawater density were correlated by 98%. Over the years 2006–2016, the front region retained 86% of larvae, but this rate yearly varied due to changes in density gradient and position of the front. For example, in 2010, 48% of larvae connected to zones south of the front when the density gradient was relatively low. In 2015, 99.2% of larvae were retained in the front region when the latitudinal front position and density gradient were relatively high. Interannual variability of the front position was potentially related to the strength and position of mesoscale circulation patterns. Our findings suggest that the larval retention on habitats favored by canyon productivity because of the front could explain the persistent abundance of A. antennatus population. This information is important to set or improve the fisheries management in zones with strong interannual hydrodynamic variability.

Large-scale geographic patterns of pelagic copepods in the southwestern South Atlantic

We compiled an extensive dataset of copepod presence/absence data to define ecoregions in the southwestern South Atlantic (33°S–55°S) and to examine their relationships to water mass characteristics. We also investigated the role of mesoscale fronts in determining the boundaries of the ecoregions. Finally, we compared copepod distributions with previously defined biogeographical provinces in the southwestern South Atlantic. The regional copepod community is organized into six assemblages that occupy distinct areas of the shelf, the shelfbreak, and the oceanic realm. These areas are characterized by different water masses. In general, the spatial configuration of the ecoregions matches that of the previously defined regional biogeographic provinces and marine fronts seem to act as boundaries between the ecoregions.

Linking the scientific knowledge on marine frontal systems with ecosystem services.

Primary production hotspots in the marine environment occur where the combination of light, turbulence, temperature and nutrients makes the proliferation of phytoplankton possible. Satellite-derived surface chlorophyll-a distributions indicate that these conditions are frequently associated with sharp water mass transitions named "marine fronts". Given the link between primary production, consumers and ecosystem functions, marine fronts could play a key role in the production of ecosystem services (ES). Using the shelf break front in the Argentine Sea as a study case, we show that the high primary production found in the front is the main ecological feature that supports the production of tangible (fisheries) and intangible (recreation, regulation of atmospheric gases) marine ES and the reason why the provision of ES in the Argentine Sea concentrates there. This information provides support to satellite chlorophyll as a good indicator of multiple marine ES. We suggest that marine fronts could be considered as marine ES hot spots.

Fixation probabilities in weakly compressible fluid flows

Competition between biological species in marine environments is affected by the motion of the surrounding fluid. An effective 2D compressibility can arise, for example, from the convergence and divergence of water masses at the depth at which passively traveling photosynthetic organisms are restricted to live. In this report, we seek to quantitatively study genetics under flow. To this end, we couple an off-lattice agent-based simulation of two populations in 1D to a weakly compressible velocity field-first a sine wave and then a shell model of turbulence. We find for both cases that even in a regime where the overall population structure is approximately unaltered, the flow can significantly diminish the effect of a selective advantage on fixation probabilities. We understand this effect in terms of the enhanced survival of organisms born at sources in the flow and the influence of Fisher genetic waves.

Marine fronts as preferred habitats for young Patagonian hoki Macruronus magellanicus on the southern Patagonian shelf

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 588:191-200 (2018) - DOI: https://doi.org/10.3354/meps12454 Marine fronts as preferred habitats for young Patagonian hoki Macruronus magellanicus on the southern Patagonian shelf Daniela Alemany1,*, Oscar O. Iribarne1, Eduardo M. Acha1,2 1Instituto de Investigaciones Marinas y Costeras (IIMyC, CONICET-UNMdP), CC 1260 Correo Central Mar del Plata, Argentina 2Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), Paeso Victoria Ocampo N°1, Esollera Norte, Mar del Plata, Argentina *Corresponding author: dalemany@yahoo.com ABSTRACT: Due to strong seasonality and spatial variation in ecosystem productivity, fish can show ontogenetic and/or seasonal changes in habitat use and move between different habitats to exploit the richest food resources. Here, we evaluate the spatial patterns of the size distribution of Patagonian hoki Macruronus magellanicus in relation to the highly productive frontal systems of the southern Patagonian shelf. Additionally, we assessed diet composition in relation to size. Fish data came from 10 scientific cruises that were carried out between April 1978 and March 1979 during cold and warm seasons of the year. Samples were collected using demersal hauls that for the purposes of this study were ascribed to frontal or non-frontal zones. Based on the analysis of the total length of 3660 Patagonian hoki individuals, a generalized linear model was constructed to evaluate the association between fish size and fronts. Moreover, prey items consumed by fish grouped into 4 size classes were evaluated by analysing the contents of 1067 stomachs. Our results showed that smaller fish (juveniles) were more frequently located along frontal areas and preyed upon zooplankton. In contrast, larger fish (adults) preyed on larger items and showed no spatial relationship with fronts. The positive relationship observed between small-sized fish and fronts may be related to the low trophic level of these fish and the abundance of small-sized prey in frontal zones. KEY WORDS: Fish size · Trophic level · Diet · Southwestern Atlantic Full text in pdf format PreviousNextCite this article as: Alemany D, Iribarne OO, Acha EM (2018) Marine fronts as preferred habitats for young Patagonian hoki Macruronus magellanicus on the southern Patagonian shelf. Mar Ecol Prog Ser 588:191-200. https://doi.org/10.3354/meps12454 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 588. Online publication date: February 08, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Spatial distribution, enrichment, and source of environmentally important elements in Batticaloa lagoon, Sri Lanka.

The present paper is the first documentation of distribution and contamination status of environmentally important elements of superficial sediments in the Batticaloa lagoon that is connected to the largest bay of the world. Surface sediment samples were collected from 34 sites covering all over the lagoon. Concentrations of elements such as As, Cr, Cu, Fe, Nb, Ni, Pb, Sc, Sr, Th, V, Y, Zn, and Zr were measured by X-ray florescence analysis. Geochemically, the lagoon has three different zones that were influenced mainly by fresh water sources, marine fronts, and intermediate mixing zones. The marine sediment quality standards indicate that Zr and Th values are exceeded throughout the lagoon. According to the freshwater sediment quality standards, Cr levels of all sampling sites exceed the threshold effect level (TEL) and 17% of them are even above the probable effect level (PEL). Most sampling sites of the channel discharging areas show minor enrichment of Cu, Ni, and Zn with respect to the TEL. Contamination indices show that the lagoon mouth area is enriched with As. Statistical analysis implies that discharges from agricultural channel and marine fluxes of the lagoon effects on the spatial distribution of measured elements. Further research is required to understand the rate of contamination in the studied marine system.

Distribution and intensity of bottom trawl fisheries in the Patagonian Shelf Large Marine Ecosystem and its relationship with marine fronts

AbstractTrawling is a major concern worldwide and there is considerable debate about its impact on marine ecosystems. The Patagonian Shelf Large Marine Ecosystem (PSLME) is an important fishing area in the Southwest Atlantic where bottom trawling is the dominant fishing method. We investigated the distribution of bottom trawl fishing within this region, defining the areas of highest trawling intensity (hotspots) and evaluating their relationship with marine fronts. We focused on the three main oceanographic fronts, the shelf‐break front, the southern Patagonia front and the mid‐shelf front. To estimate fishing effort and trawled areas, we used VMS data from 2006 to 2012. Despite being almost a fully trawlable shelf, we found that the spatial distribution of trawling activity is patchy and trawling hotspots were small, comprising annually <5% of the shelf extension or <7% of the total trawlable area. Contrary to what is believed worldwide, our findings suggest that over the PSLME the magnitude of habitat effects as a result of bottom trawling is relatively small. Regarding the three frontal systems studied, only the shelf‐break front showed a positive relationship with trawl fishing activity. Although trawling hotspots did not overlap with marine fronts, the shelf‐break front receives more trawling effort than expected. We hypothesize that this pattern is due to aggregation of species near or at the front taking advantage of the opportunities provided by this area.

Marine fronts are important fishing areas for demersal species at the Argentine Sea (Southwest Atlantic Ocean)

The high primary and secondary production associated with frontal systems attract a diversity of organisms due to high prey availability; this is why a strong relationship between fronts and pelagic fisheries has been shown worldwide. In the Argentine Sea, demersal resources are the most important, both in economical and in ecological sense; so we hypothesize that fronts are also preferred fishing areas for demersal resources. We evaluated the relationship between spatial distribution of fishing effort and oceanographic fronts, analyzing three of the most important frontal systems located in the Argentine Sea: the shelf-break front, the southern Patagonia front and the mid-shelf front. Individual vessel satellite monitoring system data (VMS; grouped by fleet type: ice-trawlers, freezer-trawlers and jigging fleet) were studied and fishing events were identified. Fishing events per area were used as a proxy of fishing effort and its spatial distribution by fleet type was visualized and analyzed with Geographic Information Systems. Oceanographic fronts were defined using polygons based on satellite chlorophyll amplitude values, and the percentage of fishing events within each polygon was calculated. Results showed a positive association between fronts and fishing activities of the different fleets, which suggests the aggregation of target species in these zones. The coupling of the freezer-trawler and jigging fleets (that operate on lower trophic level species; Macruronus magellanicus and Illex argentinus respectively) with fronts was higher than the ice-trawler fleet, targeting species of higher trophic level (Merluccius hubbsi). Marine fronts represent important fishing areas, even for demersal resources, as the distribution of fishing fleets and fishing effort are positively associated with frontal zones.

Use of marine space by Black-browed albatrosses during the non-breeding season in the Southwest Atlantic Ocean

Marine birds like albatrosses have shown a profound deterioration of their conservation status in recent years. The Black-browed albatross (Thalassarche melanophris) is the most abundant threatened albatross species in the Southwest Atlantic continental shelf. Declines in their breeding populations have been largely attributed to the impact of incidental mortality in fisheries. Data on at-sea distribution for the species during breeding is abundant, but movements of individuals during winter are poorly known. Here, we investigate the at-sea distribution of Black-browed albatrosses during the non-breeding seasons 2011 and 2012. Eleven adult individuals were captured at-sea and equipped with satellite tags. Distribution of tracked Black-browed albatrosses was mostly restricted to waters within the continental shelf of Argentina, Uruguay and southern Brazil; from 29° to 51°S. Two large marine areas, comprising the ca. 90% of the core area (50% utilization distribution) were identified; one from the mouth of Rio de la Plata toward the E and SE reaching the shelfbreak, and another in El Rincón estuary and waters to the South. Tracked birds were distributed over nine oceanographic regimes in the SW Atlantic continental shelf, spending between 5 and 34% of their time at sea in marine fronts of high productivity such as Río de la Plata, Los Patos lagoon estuary front, the shelfbreak and the mixed front. The identified core areas could be considered as proxy indicators of priority areas at the time of implementing conservation measures for the species. The analysis of overlapping with fisheries on the Argentinean Continental Shelf will provide further insights about critical areas where those measures should be more stringent.

Spatial patterns in the diversity of sharks, rays, and chimaeras (Chondrichthyes) in the Southwest Atlantic

Knowing how the diversity of sharks, rays and chimaeras (Chondrichthyes) is distributed helps us to design strategies to conserve these highly-vulnerable predators and their habitats. Here, we analyzed the spatial distribution of chondrichthyan species richness in the Southwest Atlantic (34–56oS), and its relationship with environmental variables and marine fronts, by using a dataset obtained before the major development of industrial trawling fisheries. We also explored the relationship between richness and reported catches of chondrichthyans from commercial, demersal fisheries. Generalized linear models were used to assess the relationship of species richness with environmental variables; with marine fronts and with commercial catches. Species richness increased towards the north, particularly close inshore and on the outer shelf, with cells of highest richness found north of 48oS. Dissolved oxygen was related negatively with richness; depth, latitude and longitude were also related with richness, but to a lesser extent. Chondrichthyan diversity hotspots, i.e. cells with richness higher than the 90% percentile of the richness distribution, were more likely to occur on marine fronts than elsewhere. High chondrichhtyan catches were significantly associated to hotspots, but low-catch areas were not related to coldspots, i.e. cells with less than the 10% percentile of the richness distribution. Areas of high richness of chondrichthyans coincide with high levels of catches and are used by other species of high conservation concern. Given the importance of these areas to multiple species in the Southwest Atlantic, any conservation strategy based on a network of protected areas should include marine fronts.

Shifts in an epibenthic trophic web across a marine frontal area in the Southwestern Atlantic (Argentina)

Marine benthic trophic relationships and food web structures may be influenced by benthic–pelagic coupling processes, which could also be intensified by the physical dynamics of marine fronts. In this work, we employed stable isotope (δ 13C and δ 15N) analysis to investigate the influence of the Southwest (SW) Atlantic shelf-break front (SBF; 38–39°S, 55–56°W; Argentina) on an epibenthic trophic web. Epibenthic organisms were sampled, at depths of ~ 100 m, with a non-selective dredge from a sandy bottom community located in frontal (F) and marginal (M) areas. The SBF position and the chlorophyll-a (chl-a) concentrations were inferred using satellite data of the sea surface temperature (SST) and satellite chl-a concentration, respectively. The most noticeable shifts in stable isotopes between the sampled areas were those of the Patagonian scallop, Zygochlamys patagonica (δ 13C), and those of the sea urchin, Sterechinus agassizi (δ 15N). Diet analyses inferred from stable isotopes and mixing models demonstrated that the dominant component of this community, Z. patagonica, had variable contributions to higher trophic levels between areas. More importantly, the epibenthic assemblage in F areas showed δ 13C-enriched and δ 15N-depleted isotopic signatures with respect to the M areas. Collectively, this evidence suggests that frontal dynamics promotes the accumulation of δ 13C-enriched phytoplankton in the seabed in F areas, while in M areas the more degraded organic matter becomes more important in the trophic web, decreasing the δ 15N isotopic signature of the assemblage. Therefore, the trophic web was sustained by fresher food in F areas than in M areas, demonstrating the role of frontal dynamics in the shaping of these communities.

Multi-decadal retreat of Greenland’s marine-terminating glaciers

AbstractMany marine-terminating glaciers draining the Greenland ice sheet have retreated over the past decade, yet the extent and magnitude of retreat relative to past variability is unknown. We measure changes in front positions of 210 marine-terminating glaciers using Landsat imagery spanning nearly four decades and compare decadal-scale rates of change with earlier observations. We find that 90% of the observed glaciers retreated between 2000 and 2010, approaching 100% in the northwest, with rapid retreat observed in all sectors of the ice sheet. The current retreat is accelerating and likely began between 1992 and 2000, coincident with the onset of warming, following glacier stability and minor advance during a mid-century cooling period. While it is clear an extensive retreat occurred in the early 20th century, a period of increasing air temperatures, a comparison of our results with historical observations provides evidence that the current retreat is more widespread. The onset of rapid retreat with warming relative to the slow and lagged advance with cooling suggests an asymmetry in the response of marine fronts to external forcing.

The relationship between marine fronts and fish diversity in the Patagonian Shelf Large Marine Ecosystem

AbstractAim To evaluate the relationship between marine fronts and (1) fish diversity patterns, (2) fish biomass distribution, and (3) fish assemblage structure.Location Patagonian Shelf, Southwestern Atlantic Ocean.Methods Three main frontal systems and eight nearby zones (frontal vs. non‐frontal areas) were compared. An extensive fishery database, obtained during an a priori sampling scheme (spatial resolution 1 × 1) from 1978 to 1979, was employed. Analyses of 248 trawling stations were performed using a combination of diversity measures (species richness, Shannon diversity and evenness), biomass analyses and multivariate analyses [nonparametric analysis of similarity (ANOSIM), non‐metric multidimensional scaling ordination (NMDS) and similarity percentages (SIMPER)] to evaluate the effect of fronts on fish communities.Results In total, 46 fish taxa were identified. Demersal fish diversity increased at the tidal front of Península Valdés but decreased in the frontal zones of the Southern Shelf‐Break and Magellan frontal systems. The richness and biomass of pelagic fish were higher at the Península Valdés Tidal Front, while the biomass of demersal fish was higher at its non‐frontal counterpart. Fish diversity did not differ consistently along the Northern Shelf‐Break Front. However, a higher fish biomass was registered at the non‐frontal zone. Demersal and pelagic fish assemblages differed between frontal and non‐frontal zones.Main conclusions The Patagonian Shelf Large Marine Ecosystem has diverse frontal types that appear to have different effects on fish diversity and assemblage structure. Seasonal (tidal) or permanent fronts have different effects on the parameters analysed, which could be due to productivity–diversity relationships. The Península Valdés Tidal Front, a relatively short temporal scale system, demonstrates a stronger influence on fish diversity, biomass and assemblage structure than the other frontal areas studied. The seasonality of nutrient input owing to frontogenesis, which begins during the austral spring, may play an important role in determining local diversity. At permanent frontal features, diversity decreases when the nutrient availability is high. This is potentially because, when food resources increase, a few species become dominant.

Three-dimensional distribution of larval fish assemblages across a surface thermal/chlorophyll front in a semienclosed sea

The oceanographic processes involved in marine fronts and their effects on the plankton are still a challenge in the understanding of marine ecosystems. This study examines the relationship of the three-dimensional distribution of larval fish assemblages (LFAs) with hydrography on a tidal-mixing surface thermal/chlorophyll front in the highly productive midriff archipelago of the Gulf of California during summer (August, 2005). Zooplankton samples were obtained on both sides of the front with an opening–closing net (505 μm) in 50-m strata from the surface to 200 m depth. The Bray–Curtis dissimilarity index defined three strata groups with different LFAs. On the cool side of the front, characterized by high chlorophyll, salinity, and dissolved oxygen, an LFA with the lowest larval abundance (97 larvae/10 m 2) and low taxa number (44) was defined. On the warm side of the front, where the lowest concentrations of surface dissolved oxygen and surface chlorophyll were recorded, an LFA was defined on the pycnocline, with the highest mean larval abundance and number of taxa (927 larvae/10 m 2 and 109 taxa); it was composed of epipelagic, mesopelagic, and demersal species. Also on the warm side of the front, but below the pycnocline, an LFA was observed with medium larval abundance and taxa number (126 larvae/10 m 2 and 28 taxa), formed by mesopelagic species. This assemblage was absent from the cool area to the northwest of the front, mainly from 150 to 50 m depth, where maximum-salinity water from the Northern Gulf was found. We conclude that the surface thermal/chlorophyll front had a profound effect on LFAs distribution in the surface layer, while the southward intrusion of maximum-salinity water from the Northern Gulf bounded the LFAs distribution in the deeper layer under the pycnocline. Therefore, in addition to the surface thermal/chlorophyll front, the hydrographic processes associated with the Gulf's seasonal and thermohaline circulation affect the LFAs three-dimensional distribution. Similar relationships may occur in other ocean ecosystems.

From the front

The causes of recent dynamic thinning of Greenland's outlet glaciers have been debated. Realistic simulations suggest that changes at the marine fronts of these glaciers are to blame, implying that dynamic thinning will cease once the glaciers retreat to higher ground.

Marine fronts at the continental shelves of austral South America: Physical and ecological processes

Neritic fronts are very abundant in austral South America, covering several scales of space and time. However, this region is poorly studied from a systemic point of view. Our main goal is to develop a holistic view of physical and ecological patterns and processes at austral South America, regarding frontal arrangements. Satellite information (sea surface temperature and chlorophyll concentration), and historical hydrographic data were employed to show fronts. We compiled all existing evidence (physical and biological) about fronts to identify regions defined by similar types of coastal fronts and to characterize them. Fronts in austral South America can be arranged in six zones according to their location, main forcing, key physical variables, seasonality, and enrichment mechanisms. Four zones, the Atlantic upwelling zone; the temperate estuarine zone; the Patagonian tidal zone and the Argentine shelf-break zone, occupy most of the Atlantic side. The Chile–Peru upwelling zone, on the Pacific, is the largest and best-known region. The Patagonian cold estuarine zone encompasses the tip of South America, connecting the Pacific and Atlantic oceans, and remains poorly studied. When observed at a continental scale, the Pacific coast dominated by two large frontal zones appears simplest than the Atlantic coast in terms of frontal richness. The extension of the continental shelf in the Atlantic coast allows for the development of a great diversity of mesoscale fronts. Though frontal zones we defined are extensive areas of the continental shelves, fronts inside the zones are comparatively small areas. Even so, they play a paramount role in ecological processes, allowing for high biological production; offering feeding and/or reproductive habitats for fishes, squids, and birds; acting as retention areas for larvae of benthic species; and promoting establishment of benthic invertebrates that benefit from the organic production in the frontal area.

On the air‐sea interaction in areas of thermal marine fronts in the Greenland Sea

Abstract The effects of marine fronts on the local atmospheric surface layer and air‐sea interaction were studied. Several mesoscale fronts were crossed by a research vessel in the Greenland Sea. Air temperature, humidity and stability conditions, and the fluxes of momentum, as well as sensible and latent heat, were investigated. For relatively calm conditions, close air‐sea coupling was observed in the temperature whereas for stronger winds, the air temperature of the surface layer was not markedly modified by the front below. Changes in the moisture content in the frontal area were observed and, in one case, evaporation was observed on the warm water side and condensation on the cold water side of the front. Frontal differences in heating from the sea were assumed to affect the surface‐layer wind field.