Sea Water Mass Research Articles

Water masses’ bacterial community structure and microbial activities in the Ross Sea, Antarctica

AbstractDuring the summer 2005/06, an oceanographic cruise was carried out in the Ross Sea, from Cape Adare, through the Terra Nova Bay polynya to the eastern edge of the Ross Ice Shelf. We analysed microbial activities (prokaryotic carbon production, protease, phosphatase, beta-glucosidase and lipase activity) and bacterial community structure (using Denaturing Gradient Gel Electrophoresis - DGGE) in order to establish if differences in bacterioplankton assemblages and their metabolic requirements occur within the five Ross Sea water masses: Antarctic Surface Waters (AASW), High Salinity Shelf Water (HSSW), Ice Shelf Water (ISW), Antarctic Bottom Water (AABW), Circumpolar Deep Water (CDW). Differences in activities were found between the highly active AASW and all the other water bodies. A Principal Component Analysis highlighted two main gradients: in the Cape Adare area (AASWn, CDW and AABW) higher phosphatase, lipase and glycolytic activities, increasing towards the surface, were identified, whereas in the southern sector of the basin [AASWs and (m)HSSW] higher leucine uptake and polypeptide degradation characterized the second gradient. DGGE fingerprinting showed for the first time that different water masses harboured diverse bacterial communities, highlighting the high specificity of deep water assemblages.Alpha- andGammaproteobacteriarepresented the main phylogenetic groupings in all samples and no substantial difference in the phylogenetic composition of assemblages was found between different water masses.

A model for predicting changes in the electrical conductivity, practical salinity, and absolute salinity of seawater due to variations in relative chemical composition

Abstract. Salinity determination in seawater has been carried out for almost 30 years using the Practical Salinity Scale 1978. However, the numerical value of so-called practical salinity, computed from electrical conductivity, differs slightly from the true or absolute salinity, defined as the mass of dissolved solids per unit mass of seawater. The difference arises because more recent knowledge about the composition of seawater is not reflected in the definition of practical salinity, which was chosen to maintain historical continuity with previous measures, and because of spatial and temporal variations in the relative composition of seawater. Accounting for these spatial variations in density calculations requires the calculation of a correction factor δSA, which is known to range from 0 to 0.03 g kg−1 in the world oceans. Here a mathematical model relating compositional perturbations to δSA is developed, by combining a chemical model for the composition of seawater with a mathematical model for predicting the conductivity of multi-component aqueous solutions. Model calculations for this estimate of δSA, denoted δSRsoln, generally agree with estimates of δSA based on fits to direct density measurements, denoted δSRdens, and show that biogeochemical perturbations affect conductivity only weakly. However, small systematic differences between model and density-based estimates remain. These may arise for several reasons, including uncertainty about the biogeochemical processes involved in the increase in Total Alkalinity in the North Pacific, uncertainty in the carbon content of IAPSO standard seawater, and uncertainty about the haline contraction coefficient for the constituents involved in biogeochemical processes. This model may then be important in constraining these processes, as well as in future efforts to improve parameterizations for δSA.

Connecting export fluxes to plankton food-web efficiency in the Black Sea waters inflowing into the Mediterranean Sea

The short-time scale evolution of plankton carbon partitioning and downward flux in the modified Black Sea water (BSW) mass entering the northeast Aegean Sea was studied using a Lagrangian approach (6-10 April 2008). The free-drifting sediment trap positioned at the bottom of the BSW layer and the control drifter, followed the same path within the anticyclone that circulates the BSW in the area. Zooplankton biomass increased (from 159 to 292 mg C m -2 ), as did faecal pellet production (from 5 to 8 mg C m -2 day -1 ), whereas a generally decreasing trend was displayed by particulate organic carbon (POC) (from 2099 to 1440 mg C m -2 ), net primary production and biomass of plankton cells >5 μm (from 32 to 11 mg C m -2 day -1 and from 153 to 124 mg C m -2 , respectively). At the same time, the organic carbon flux increased (from 131 to 311 mg C m -2 day -1 ), due to the contribution of zooplankton detritus (from 30 to 165 mg C m -2 day -1 ). Normalized biomass-size spectra slopes suggest an elevated grazing pressure upon microplankton cells and a non-steady-state ecosystem. Moreover, both the overall shallow slope values and their high correlation to organic carbon flux indicate an increased efficiency of energy transfer to higher trophic levels.

Observed characteristics of the North Yellow Sea water masses in summer

In this paper, we characterize the North Yellow Sea (NYS) water masses in summer by analyzing temperature and salinity data surveyed in 2006. The Liaonan Coastal Water is characterized by low salinity westward and southward flow paths. The westward path flows parallel to land, turns to the south, then to the southeast adjacent to the mouth of the Lushun River, where it mixes with other coastal water directly to the southwest. It becomes the main source of low salinity water in the deep water area west of 123°E. The high-salinity Lubei Coastal Water is the remnant of the winter Lubei Coastal Water, which is located mostly in a small area between Yantai and Weihai, and does not originate in the Bohai Sea Coastal Water. The two NYS zones demarcated at 123°E have distinctly different temperature and salinity characteristics. There are two high-salinity centers east of 123°E, whereas there is low-salinity water to the west whose temperature and salinity structures are complex, composed of the coastal water south of Chengshantou, the Liaonan Coastal Water and the Bohai Sea Water.

Long term sea level change and water mass balance in the South China Sea

Sea level anomalies observed by altimeter during the 1993–2006 period, thermosteric sea level anomalies estimated by using subsurface temperature data produced by Ishii and SODA reanalysis data, tide gauge records and HOAPS freshwater flux data were analyzed to investigate the long term sea level change and the water mass balance in the South China Sea. The altimeter-observed sea level showed a rising rate of (3.5±0.9) mm yr−1 during the period 1993–2006, but this figure was considered to have been highly distorted by the relatively short time interval and the large inter-decadal variability, which apparently exists in both the thermosteric sea level and the observed sea level. Long term thermosteric sea level from 1945 to 2004 gave a rising rate of 0.15±0.06 mm yr−1. Tide gauge data revealed this discrepancy and the regional distributions of the sea-level trends. Both the ‘real’ and the thermosteric sea level showed a good correspondence to ENSO: decreasing during El Nino years and increasing during La Nina years. Amplitude and phase differences between the ‘real’ sea level and the thermosteic sea level were substantially revealed on both seasonal and interannual time scales. As one of the possible factors, the freshwater flux might play an important role in balancing the water mass.

Humidification–dehumidification desalination system driven by geothermal energy

The work presented in this paper focuses on desalinating sea water system using a humidification–dehumidification process as it is supplied with water heated by geothermal energy as clean and renewable natural resources of energy. Computer simulation of the behavior under various working conditions of the desalination system was carried out to predict the variations of key output. Such variables include the ratio of sea water mass flow rate related to air mass flow rate, cooling water temperature difference across the condenser, geothermal source inlet temperatures to the heat exchanger and the amount of produced distilled water. To validate the computer program, a comparison between the experimental and theoretical results was conducted, and a good agreement had been obtained. The result showed that, the optimum value of the ratio between sea water mass flow rate to air mass flow rate was found to be in the range of 1.5 to 2.5. Improvement in the fresh water productivity at the optimum ratio of sea water mass flow rate to the air flow rate was observed by increasing both the geothermal source inlet temperature and the cooling water temperature difference across the condenser.

Sedimentation and particle dynamics in the seasonal ice zone of the Barents Sea

The Barents Sea seasonal ice zone (SIZ) is one of the most dynamic areas in the world ocean. This biologically productive area undergoes extreme intra- and inter-annual variabilities in sea ice and water mass transport properties. Here, we investigate seafloor burial processes in three regions of the SIZ with different ice-cover frequencies: predominantly open water (POW), marginally ice-covered (MIC), and predominantly ice-covered (PIC) with approximately 0, 10 and 50% sea ice cover, respectively, in 2002–2003. Down-core sediment profiles of the radionuclides 234Th, 210Pb, and 137Cs, along with sediment carbon, nitrogen and phosphorus concentrations are examined in two to three cores from each region. Sedimentation rates and velocities using 210Pb ex (excess 210Pb) profiles and assuming negligible mixing below a surface mixed layer are relatively uniform throughout the study area, averaging 558 ± 154 g m − 2 y − 1 and 1.1 ± 0.4 mm y − 1 ( n = 7). These sedimentation velocities are confirmed using 137Cs (1.0 ± 0.4 mm y − 1 , n = 7). 234Th ex (excess 234Th) derived bioturbation rates are positively correlated with number of benthic individuals per 0.5 m 2 ( R 2 = 0.83) and exhibit a pattern of higher rates in the MIC (14.5 ± 2.1 cm − 2 y − 1) relative to both the POW (6.3 ± 2.2 cm − 2 y − 1) and PIC (5.3 ± 1.2 cm − 2 y − 1) ( p < 0.01). 234Th ex inventories are also significantly higher ( p = 0.026) within the MIC, while both 210Pb ex and 137Cs sediment inventories are more regionally uniform. Furthermore, organic carbon (C org) and total nitrogen (N tot) concentrations are relatively high in both the MIC and PIC compared to POW. For this limited data set, higher bioturbation rate coefficients and higher 234Th ex sediment inventories in the MIC relative to the other sampled regions, suggest that the MIC exhibits a greater predominance of marine versus terrestrial sediment sources that support enhanced scavenging and benthic biological activity. These results suggest that a climate-driven northward shift in sea ice will result in a corresponding shift in benthic communities that currently depend upon surface derived fluxes of organic matter associated with the present-day location of the ice edge in the Barents Sea.

Effect of design parameters on multi-effect desalinationsystem specifications

Potable water supply has a significant role in today's developing world. It is very important to determine the specifications of desalination systems in order to achieve cheaper water prices and better operational conditions. Multi-effect desalination (MED) with thermal vapor compressor (TVC) is a progressing, low cost and easy operating system to produce drinking and pure water for both social and industrial applications. In this paper, the effects of different design parameters such as number of evaporation effects, inlet steam pressure, temperature difference of the effects, and feed water temperature on MED system specifications, i.e. performance ratio, required heat transfer area and cooling sea water, are studied. The results show that there is an optimum value for the number of effects for a system with constant production capacity. This optimum value is a function of seawater salinity, effects temperature difference and feed water temperature. The results also show that the increase of inlet steam pressure increases the performance ratio and the required heat transfer surface area of the system and decreases the cooling seawater mass flow rate.

Temporal and spatial distribution of 137Cs in Eastern Mediterranean Sea. Horizontal and vertical dispersion in two regions

Caesium-137 activity concentration in the water columns of the Gulf of Patras (Central Greece) and the North-Eastern Aegean Sea (easterward to Lemnos Island) was investigated in selected sampling stations during the period September 2004–June 2006. The methodology followed was based on the sorption of caesium (Cs) on cotton wound cartridge filters impregnated by Cu 2[Fe(CN) 6] via in-situ pumping. In terms of the horizontal and vertical records, the activity concentrations of 137Cs in the Gulf of Patras ranged between 1.2 and 6.7 Bq m −3, depending on the sampling period and the prevailing physicochemical regime at the sampling station. The general pattern of the decreased activity concentrations of 137Cs with increasing depth was reversed in the Gulf of Patras during the cold period attributed to the prevailing advective processes of the area. The activity concentrations of 137Cs in the North-Eastern Aegean Sea ranged from 2.6 to 12.8 Bq m −3, whereas significant stratified curves were observed during the warm period and also, in one station during the cold period. In terms of temporal variation, the discharges in the Gulf of Patras resulted in enhanced levels of 137Cs, whereas in the North Aegean Sea the incoming water masses form the Black Sea had an apparent influence throughout the year by increasing the 137Cs levels, hence presenting a weak seasonal variation. Comparing the two studied areas, one could say that the North Aegean Sea, as an open sea environment, presented higher concentrations due to the influence of the Black Sea water masses. The estimated inventories of 137Cs in the Gulf of Patras ranged 0.25 ± 0.03–0.79 ± 0.03 kBq m −2, whereas in the North-Eastern Aegean Sea they ranged 0.33 ± 0.02–0.92 ± 0.03 kBq m −2.

Persistent Scatterers InSAR to detect ground deformation over Rio-Antirio area (Western Greece) for the period 1992–2000

The aim of this paper is to detect ground deformation detection in the Rio-Antirio area (Western Greece), between 1992 and 2000. The construction of Rio-Antirio bridge, commenced in year 2000 and completed in 2004 when its operation was launched, demands the study of the historic deformation of the broader area. The Interferometric Point Target Analysis (IPTA) was applied using a dataset of 42 ERS-1 and 2 scenes. Two separate IPTA processing were performed using different reference points for Rio and Antirio respectively. It would not be possible to unwrap the entire scenes using a single reference point because of the presence of the sea water mass between Rio and Antirio. The majority of the point targets show subsidence for the area of Rio ranging between − 1.8 mm/year and − 6.2 mm/year and for the Antirio area stability or subsidence rates of less than 2 mm/year. Additionally, the deformation history for a number of point targets for both areas was investigated. The detected subsidence of the coastal plains and specially this of Rio could be attributed to the presence of active faults as the area is located over the hanging wall of the fault zone.

DO Environments in Tidal Rivers with Massive Fish Death

Although massive fish death was mostly observed in tidal rivers and mainly caused by hypoxic water mass, there was little information on DO environments in large tidal rivers. To investigate DO environments in tidal rivers with and without massive fish death, we conducted field measurements on hydrodynamics and water quality environments in the Sumidagawa and Arakawa Rivers. In summer, larger intrusion of sea water was found in Sumidagawa River than Arakawa River mainly due to the difference of river discharges, and then DO concentration in the Sumidagawa River was relatively lower than in the Arakawa River. Also found that the intrusion of hypoxic seawater mass and inflows of CSO due to hydrologic events have an important role on reduction of DO concentration in the Sumidagawa River.

A recount of Ross Sea waters

Abstract Oceanographic observations within the Ross Sea have grown dramatically in recent years, both in number and quality. This has prompted a parallel recount of the circulation and structure of all water masses in the southwestern continental margins of the Pacific Ocean. A high-resolution set of horizontal property distributions was combined into a new climatology, which in turn is the basis of a fine volumetric θ − S census of all Ross Sea water masses. Inshore of the shelf break (700 m isobath) the Ross Sea volume (25×10 4 km 3 ) partitioning into layers of neutral density ( γ n ) is: 25% in the top layer ( γ n −3 ) of Antarctic Surface Water (AASW), 22% in the middle layer (28.00 kg m −3 γ n −3 ) of oceanic thermocline water (12%) and Modified Circumpolar Deep Water (MCDW; 10%), and 53% in the bottom layer ( γ n >28.27 kg m −3 ) of Shelf Water (SW, θ θ >−1.85 °C; 22%), precursor of the Antarctic Bottom Water (AABW) offshore. AASW flows westward along the outer shelf and southward along the eastern coast past Cape Colbeck. Oceanic thermocline waters (28.00 kg m −3 γ n −3 ) cross the shelf break west of 170°W and follow southward paths along banks, shoaling progressively to near the sea surface of the central and western inner shelves. Winter buoyancy loss converts AASW and oceanic thermocline water into denser types of MCDW and SW, which move cyclonically toward the sills of major troughs. The census shows a continuous mode of relatively dense MCDW (28.10 kg m −3 γ n −3 ) directly linked to the Circumpolar Deep Water (CDW) offshore, effectively ventilating and freshening the deep ocean at levels below the salinity maximum and above AABW. MCDW outflows from the Ross Sea shelf are traced to the Antarctic Circumpolar Current: near 155°E, into the Australian-Antarctic Basin, along the northern flank of the Southwest Pacific Ridge, and to near 135°W, past the eastern end of the Ross Gyre. Two sources of salty SW are inferred near the coastal polynyas in the Terra Nova Bay and western Ross Ice Shelf areas. The latter contributes to a major outflow of Ice SW that reaches the shelf break along 180°. Vertical mixing of MCDW and SW produce MSW over the shelf, continuing over the sills as new AABW. Export of low salinity AABW ( S

Natural background of hydrocarbon gases (C1–C5) in the waters of the Kara Sea

The distributions of methane and hydrocarbons (HC) C2+ throughout the vertical section of the water mass and sediments of the Kara Sea and the estuaries of the Ob and Yenisei rivers were examine during expeditions aboard the R/V “Akademik Boris Petrov” in 1997–2002. Data obtained during the expeditions and extensive information provided by the complex study of the carbon cycle in the aquatic area were used to analyze the genesis of hydrocarbon gases in marine water. The example of particulate matter was used to demonstrate that hydrocarbon gases of the composition C2–C5 contained in seawater are genetically related to aquatic organic matter (OM), regardless of seawater salinity. The hydrocarbon complex is dominated (80%) by higher C4–C5 homologues. The concentration of C4–C5 hydrocarbons in the estuarine fresh waters is comparable with the high methane concentration (2–3 μl/l), drastically decreases in the zone of water mixing, and then rapidly increases to values several times higher than the methane concentration in seawater outside the outer boundary of the sedimentation depocenter of riverine particulate matter. A direct correlation was established for the concentration of the C4 + C5 homologues with the OM of the water mass, and the leading role was demonstrated to be played by labile OM of the autochthonous biomass (marine phytoplankton) in the genesis of higher hydrocarbon gases (alkenes, alkanes, and isoalkanes) during the early diagenetic stage of OM transformations in water. Along with the biomass of phytoplankton, a significant role in the genesis of C2–C3 hydrocarbons is played by destruction products of terrigenous OM. The destruction of OM and generation of gaseous hydrocarbons, including methane, are restricted to the pycnocline and the water-sediment interface. The absolute predominance of the sum of the C4 + C5 homologues in the hydrocarbon C2+ gases and the presence of unsaturated C2–C4 hydrocarbons are typical of the natural background of hydrocarbons of the Kara Sea water mass.

Antarctic records of precession‐paced insolation‐driven warming during early Pleistocene Marine Isotope Stage 31

Precisely dated Antarctic continental margin and Southern Ocean geological records show that the early Pleistocene interglacial Marine Isotope Stage 31 (MIS‐31) was characterized by warmer than present surface waters with reduced sea‐ice and enhanced high latitude marine carbonate production. Micropaleontologic, isotopic, and paleomagnetic evidence from drill cores at 77°S (Cape Roberts Project‐1) and 53°S (ODP Site 1094) indicate circumantarctic changes in sea surface temperature and water mass stratification that are in phase with high southern latitude insolation changes during MIS‐31. These changes imply a significant, though as yet unquantifiable reduction in Antarctic ice volume. This study supports the hypothesis that the interhemispheric antiphased relationship of the precession cycle attenuates a potentially significant Antarctic ice volume signal in the deep sea oxygen isotope record. The implications are that Antarctic marine ice sheets may be more susceptible to warming and high insolation driven retreat than has been widely recognized.

Comment on “On the steric and mass‐induced contributions to the annual sea level variations in the Mediterranean Sea” by David García et al.

[1] Garcia et al. [2006] (hereafter referred to as GCDVG) present an analysis of mass-induced sea level variation (SLVmass) of the Mediterranean Sea based on satellite altimetry, ocean modeling and Gravity Recovery and Climate Experiment (GRACE) gravity measurements. In particular, GCDVG find consistency between altimeter sea level variations corrected for steric effects and changes in oceanic mass derived from Gravity Recovery and Climate Experiment (GRACE). GCDVG show that the annual cycle of the sea level variability (SLVtotal) is dominated by changes in its steric part (SLVsteric) and that the basin average of mass (SLVmass) is maximum in February. They conclude that, when the sea level is rising (falling) the Mediterranean Sea is actually losing (gaining) mass. [2] GCDVG appear to use an unrealistically large estimate of steric sea level variability (SLVsteric) and neglect changes in continental water storage that can significantly affect GRACE measurements over the Mediterranean Sea. These issues are examined in turn below by reviewing relevant individual basin averages of the Mediterranean Sea in comparison to results of other studies. In particular, while also finding consistency between altimetry and GRACE measurements, Fenoglio-Marc et al. [2006] (hereafter referred to as FKB), in a similar study of the Mediterranean Sea, find steric effects only accounting for about 60% of the total annual sea level variability and the annual cycle of SLVmass having a maximum in November.

Hydrography and biogeochemistry of the north western Bay of Bengal and the north eastern Arabian Sea during winter monsoon

The north eastern Arabian Sea and the north western Bay of Bengal within the Indian exclusive economic zone were explored for their environmental characteristics during the winter monsoons of 2000 and 2001 respectively. The two regions were found to respond paradoxically to comparable intensities of the atmospheric forcing. There is an asymmetry in the net heat exchange of these two basins with atmosphere because of the varying thickness of barrier layer. During winter, the convective mixing in the Arabian Sea is driven by net heat loss from the ocean, whereas the Bay of Bengal does not contribute to such large heat loss to the atmosphere. It appears that the subduction of high saline Arabian Sea water mass is the mechanism behind the formation of a barrier layer in the northeast Arabian Sea; whereas that in the Bay of Bengal and the southeast Arabian Sea are already established as due to low saline water mass. The weak barrier layer in the Arabian Sea yields to the predominance of convective mixing to bring in nitrate-rich waters from the deeper layers to the surface, thereby supporting enhanced biological production. On the other hand, the river discharge into the Bay of Bengal during this period results in the formation of a thick and stable barrier layer, which insulates vertical mixing and provide oligotrophic condition in the Bay.

Dinoflagellate cysts in the surface sediments of the White Sea

Dinoflagellate cysts were studied in 42 samples from the surface sediments of the White Sea. The total concentration of dinocysts varies from single cysts to 25 000 cyst/g of dry sediments, which reflects the biological productivity in the White Sea waters and the regional particular features of the sedimentation processes. The highest concentrations are observed in silts; they are related to the regions of propagation of the highly productive Barents Sea waters in the White Sea. Generally, the spatial distribution of dinocysts species in the surface sediments corresponds to the distribution of the major types of water masses in the White Sea. The cysts of the relatively warm-water species (Operculodinium centrocarpum, Spiniferites sp.) of North Atlantic origin that dominate in the sediments indicate an intensive intrusion of the Barents Sea water masses to the White Sea along with hydrological dwelling conditions in the White Sea favorable for the development of these species during their vegetation period. The cold-water dinocyst assemblage (Islandinium minutum, Polykrikos sp.) is rather strictly confined to the inner parts of shallow-water bays, firstly, those adjacent to the Onega and Severnaya Dvina river mouths.

The Red Sea and the Mediterranean–Dead Sea canal project

As a mega-project which will affect the environment, the feasibility of this project must be very thoroughly studied, especially the changing limnology of the Dead Sea. The amount of the desalinated water produced by this project might be significant for the region. The saved external sources of energy to produce drinking water in these projects is between 20% to 30%, only comparing to operation along the sea taking into account the pumping of the desalinated water to Amman and Hebron. The stratification and dilution of the Dead Sea water mass with seawater may cause losses for the Dead Sea Works and the Arab Potash Company, precipitation of gypsum and change the biological environment of the upper water mass.

Sea-level forcing of carbon isotope excursions in epeiric seas: implications for chemostratigraphy

Five new δ13C excursions are reported from the Upper Ordovician Galena Group of Iowa. The δ13Ccarb and δ13Corg trends are compared to sea-level trends based on conventional sedimentological and novel chemostratigraphic (εNd) methods. It is found that rising δ13C values occur during rising sea level, peak-magnitude δ13C values are coincident with inferred peak flooding, and declining δ13C values occur with declining sea levels. The relationship to sea level is explained by a simple model of episodic flooding of the Galena platform by cool, oxygen-depleted, nutrient-rich, bottom waters originating from the Sebree Trough, which was itself connected to the nearby Iapetus Ocean. Flooding of the inner Galena shelf during sea-level transgressions caused local changes in the carbon isotope balance of inner shelf waters due to (1) locally increased primary productivity and organic carbon burial, (2) locally increased exchange of 13C-enriched dissolved inorganic carbon (DIC) with surrounding epeiric sea water masses and the surface ocean, and (3) locally decreased 12C-weathering fluxes from the Transcontinental Arch. A sea-level driver of local C-cycle perturbations complicates the use of carbon isotopes as a chemostratigraphic tool because local and eustatic controls on sea level may combine to create different secular records of relative sea-level change in stratigraphically equivalent deposits of epeiric seas.

Four Climate Cycles of Recurring Deep and Surface Water Destabilizations on the Iberian Margin

Centennial climate variability over the last ice age exhibits clear bipolar behavior. High-resolution analyses of marine sediment cores from the Iberian margin trace a number of associated changes simultaneously. Proxies of sea surface temperature and water mass distribution, as well as relative biomarker content, demonstrate that this typical north-south coupling was pervasive for the cold phases of climate during the past 420,000 years. Cold episodes after relatively warm and largely ice-free periods occurred when the predominance of deep water formation changed from northern to southern sources. These results reinforce the connection between rapid climate changes at Mediterranean latitudes and century-to-millennial variability in northern and southern polar regions.