Polar Zone Research Articles

The mechanistic basis and adaptive significance of cross-tolerance: a 'pre-adaptation' to a changing world?

Protective responses are pivotal in aiding organismal persistence in complex, multi-stressor environments. Multiple-stressor research has traditionally focused on the deleterious effects of exposure to concurrent stressors. However, encountering one stressor can sometimes confer heightened tolerance to a second stressor, a phenomenon termed 'cross-protection'. Cross-protection has been documented in a wide diversity of taxa (spanning the bacteria, fungi, plant and animal kingdoms) and habitats (intertidal, freshwater, rainforests and polar zones) in response to many stressors (e.g. hypoxia, predation, desiccation, pathogens, crowding, salinity, food limitation). Remarkably, cross-protection benefits have also been shown among emerging, anthropogenic stressors, such as heatwaves and microplastics. In this Commentary, we discuss the mechanistic basis and adaptive significance of cross-protection, and put forth the idea that cross-protection will act as a 'pre-adaptation' to a changing world. We highlight the critical role that experimental biology has played in disentangling stressor interactions and provide advice for enhancing the ecological realism of laboratory studies. Moving forward, research will benefit from a greater focus on quantifying the longevity of cross-protection responses and the costs associated with this protective response. This approach will enable us to make robust predictions of species' responses to complex environments, without making the erroneous assumption that all stress is deleterious.

Distribution, hosts and long-term decline in abundance of the Patagonian lamprey inferred from diet assessment of albatrosses

Knowledge of lampreys during their marine phase is limited, and for the southern hemisphere species was gleaned from their predators (albatrosses) in the 1970s. Taking advantage of new methodologies and long-term data on predator diet and distributions, we infer diverse aspects of lamprey distribution and ecology. DNA analyses indicated that albatrosses at South Georgia prey on Patagonian lamprey Geotria macrostoma, originating from Argentina. Their core pelagic distribution when free swimming appears to be the Antarctic Polar Frontal zone (APFZ), and not South Georgia waters as assumed previously. If so, the APFZ would be the first known hotspot in abundance of an anadromous lamprey in oceanic waters. We could not identify a teleost fish that would be a likely host. Instead, we infer that the lamprey may prey on baleen whales, based on comparison of stable isotope ratios in lamprey with candidate host species, timing of appearance in albatross diets coincident with whale migrations, and circumstantial evidence (unexplained scarring recorded during the whaling era). We suggest that the lamprey do not tolerate cold Antarctic waters, and detach from southerly-migrating whales at the thermal boundary of the APFZ, where they become accessible to albatrosses in surface waters. Given strong evidence that relative importance of prey in seabird diets reflects availability in foraging areas, the steep decrease in the annual consumption of lamprey by albatrosses at South Georgia from > 550 tonnes in 1975–1976 and 1986, to very low levels in most years since 2012, is likely to indicate a major population decrease. Despite our unconventional means of assessing the population trend, there is a compelling case for listing of Patagonian lamprey at least as Near threatened by the International Union for the Conservation of Nature, and an urgent need to better understand anthropogenic threats in Argentina.

Theoretical and numerical simulation research about annular nozzle parameters influence on heat transfer in hot-water ice-coring drilling

Ice cores from polar zones could determine ice dating and biodiversity. Ice cores retrieved in hot-water ice-coring drilling partly melted owing to moderate drilling speed of annular drill head with many nozzles, which was largely depended on the heat transfer efficiency of jet to ice at borehole bottom. To obtain the higher drilling speed and ice cores of good quality, this paper explored the influence of nozzle parameters on the heat transfer efficiency of annular jet to bottom ice. Main nozzle parameters affecting the heat transfer efficiency were theoretically determined firstly. Then influence law of nozzle parameters on the heat transfer were estimated by theoretical calculation and numerical simulation. The result showed the heat transfer of annular jet to bottom ice was positively correlated with the nozzle flow and negatively relevant with the nozzle diameter, nozzle angle and nozzle quantity, which was further compared with the drilling speed value in experiment to confirm its correctness. The angle was proved to be the most influential parameter, when it increased from 0° to 30°, the drilling speed decreased 75%. The result can provided reference for designers on how to promote the drilling speed in hot-water ice-coring drilling and improve ice core quality.

Browning and blueing – what is the fate of polar coasts?

Covered by extensive ice sheets that often terminate as ice shelves or tidewater glaciers, polar coasts are also seasonally surrounded by sea ice. However, this “whitescape” is shrinking rapidly; the years 2012 and 2022 saw sea-ice minima for the Arctic and the Antarctic, respectively. The loss of ice is transforming these coastal areas, especially in the Arctic and West Antarctica. Meltwater transports particles, called glacial flour, from land to ocean, and when intensive enough this discharge creates “brown zones” across fjords in summer. Turbid glacial plumes hinder light penetration and darken coastal waters, thereby limiting photosynthesis, while turbulent mixing induces aggregation of particles and the resulting formation of so-called marine snow (clumps of largely organic matter that coalesce and sink through the water column) (Sci Total Environ 2021; doi.org/10.1016/j.scitotenv.2021.146491). When these particles reach the seabed, they cover benthic organisms such as this macroalga (Himantothallus grandifolius), photographed in Mackellar Inlet (62°S, Antarctic Peninsula) – a glaciomarine fjord that has not “browned” yet. Furthermore, warming intensifies iceberg calving and thus likely increases the risk of ice-scouring to benthic macroalgae in the shallows. However, glacial retreat also exposes new shallow-water habitats; by allowing phytoplankton blooms and seaweed expansion in these newly ice-free areas, this exposure process (“blueing”) increases carbon accumulation in marine systems (“blue carbon”), particularly in fjords, due to their high storage-to-sequestration efficiency (Sci Nat 2021; doi.org/10.1007/s00114-021-01748-8). In polar coastal zones, many climate-change–related feedbacks are anticipated. It is therefore crucial to assess the carbon sinks emerging due to marine ice losses; though little known, these sinks provide important negative feedbacks to climate change that could be recognized as a nature-based solution. To what extent will blueing balance the effects of advancing brown zones?

An Estimation of the Geometrical Structure of Polar Cap and Emission Property of Radio Pulsar: A Treatment from an Analytical Approach

Pulsars are believed to be one of the most interesting objects in the universe. The emission mechanism of pulsars is still a conundrum to physicists, as there is no completely acceptable theory that can establish a consensus between theory and observation. Pulsars possess a gigantic magnetic field, to the order of 1012 Gauss, and generate a very powerful radio beam from the magnetic pole. However, the powerful radio beam is generated by some complicated coherent plasma processes and acceleration in the pulsar magnetosphere. The location of the origin of the radio waves has been predicted to come out exclusively from the polar cap zone, whose boundary is defined by the footprint of the last open field line. However, in this paper, we mainly try to generate the shape of the polar cap structure from an analytical solution and discuss how it gets distorted for different geometrical parameters due to the presence of perturbation such as polar cap current flow. Also, apart from that, we try to emphasize understanding the variation of radio emission height and polarization angle with respect to different geometry-related parameters as well as with frequency.

Satellite Remote Sensing of Surface Winds, Waves, and Currents: Where are we Now?

AbstractThis review paper reports on the state-of-the-art concerning observations of surface winds, waves, and currents from space and their use for scientific research and subsequent applications. The development of observations of sea state parameters from space dates back to the 1970s, with a significant increase in the number and diversity of space missions since the 1990s. Sensors used to monitor the sea-state parameters from space are mainly based on microwave techniques. They are either specifically designed to monitor surface parameters or are used for their abilities to provide opportunistic measurements complementary to their primary purpose. The principles on which is based on the estimation of the sea surface parameters are first described, including the performance and limitations of each method. Numerous examples and references on the use of these observations for scientific and operational applications are then given. The richness and diversity of these applications are linked to the importance of knowledge of the sea state in many fields. Firstly, surface wind, waves, and currents are significant factors influencing exchanges at the air/sea interface, impacting oceanic and atmospheric boundary layers, contributing to sea level rise at the coasts, and interacting with the sea-ice formation or destruction in the polar zones. Secondly, ocean surface currents combined with wind- and wave- induced drift contribute to the transport of heat, salt, and pollutants. Waves and surface currents also impact sediment transport and erosion in coastal areas. For operational applications, observations of surface parameters are necessary on the one hand to constrain the numerical solutions of predictive models (numerical wave, oceanic, or atmospheric models), and on the other hand to validate their results. In turn, these predictive models are used to guarantee safe, efficient, and successful offshore operations, including the commercial shipping and energy sector, as well as tourism and coastal activities. Long-time series of global sea-state observations are also becoming increasingly important to analyze the impact of climate change on our environment. All these aspects are recalled in the article, relating to both historical and contemporary activities in these fields.

Polar localization of new flavonoids from aerial parts of Scleranthus perennis and Hottonia palustris and their modulatory action on lipid membranes properties

The aim of this study was to characterize, for the first time, the interactions, location, and influence of flavonoids isolated from aerial parts of Scleranthus perennis (Caryophyllaceae) and Hottonia palustris (Primulaceae) on the properties of model lipid membranes prepared from dipalmitoylphosphatidylcholine (DPPC) and egg yolk phosphatidylcholine (EYPC). The tested compounds incorporated into liposomes into the region of the polar heads or at the water/membrane interface of DPPC phospholipids. Spectral effects accompanying the presence of polyphenols revealed their effect on ester carbonyl groups apart from SP8. All polyphenols brought about reorganization of the polar zone of liposomes as it was observed by FTIR technique. Additionally, fluidization effect was noted in the region of symmetric and antisymmetric stretching vibrations of the CH2 and CH3 groups with exception to HZ2 and HZ3. Similarly, in EYPC liposomes, they interacted mainly with the regions of the choline heads of the lipids and had various effects on the carbonyl ester groups with exception to SP8. The region of polar head groups is restructured due to the presence of the additives in liposomes. The outcomes obtained using the NMR technique confirmed the locations of all of the tested compounds in the polar zone and indicated a flavonoid-dependent modifying effect towards lipid membranes. HZ1 and SP8 raised motional freedom in this region whereas opposite effect was revealed for HZ2 and HZ3. In the hydrophobic region restricted mobility was noted. In this report we discuss the mechanism of previously undescribed flavonoids in terms of their actions on membranes.

Historical regional climate changes in Japan in winter as assessed by a 5-km regional climate model with a land surface process

We investigate historical regional climate changes in Japan from 1959 to 2020, analyzing a high-resolution dynamical downscaling forced by the Japanese 55-year Reanalysis (JRA-55). One-year continuous simulations are conducted by the non-hydrostatic regional climate model with a land surface model that includes the snow accumulation process, which enables us to evaluate the seasonal variation of snow cover in all of Japan. Our simulation reproduces interannual variations of the annual mean surface air temperature and annual total precipitation, and it shows rapid warming since around 1980. The annual maximum snow depth and annual maximum daily snowfall show significant decreasing trends at lower elevations on the Japan Sea sides of eastern and western Japan. Areas at higher elevations in eastern Japan show no trend in the maximum snow depth and a significant increasing trend in the maximum daily snowfall. In northern Japan, altitudinal dependencies in snow depth and snowfall changes are smaller on the Japan Sea side than on the Pacific Ocean side: the Japan Sea side shows insignificant changes in snow depth at all elevations, while the Pacific Ocean side shows decreasing and significant increasing trends at lower and higher elevations, respectively. The total number of snow-covered days is decreasing at most elevations in all regions, while the rate of decrease is smaller at higher elevations and latitudes. Composite analyses of annual maximum daily snowfall events at one prefectural city facing the Japan Sea in central Japan indicate that heavy daily snowfall occurs when the Japan Polar air mass Convergence Zone appears over the Japan Sea and the snowfall amounts show increasing and decreasing trends over the mountainous and coastal areas, respectively, due to historical warming and moistening. Our results are basically consistent with previous studies that have focused on future changes in snow depth and snowfall.

Variations of Supercooling Capacity in Intertidal Gastropods.

Winter low-temperature confines species distribution. Intertidal gastropods are distributed from tropical to polar zones, facing variable intensities and durations of low temperatures. They usually set their supercooling points (SCPs) at high subzero temperatures to stimulate freezing. However, the variations in SCP in intertidal gastropods at intraspecific and interspecific levels remain poorly understood. Here, we measured the body size, cooling rate, and SCP of nine intertidal gastropod species in China. These species were distributed in high or middle intertidal zone with different geographic distributions. The average SCPs (-4.27~-7.10 °C) and the coefficients of variation of SCP (22.6%~45.9%) were high in all species. At the intraspecific level, the supercooling capacity was positively correlated with the cooling rate. Interspecifically, the supercooling capacity was closely related to the cooling rate, and also to the species' geographical distribution. Northern high-shore species showed lower SCPs, while southern high-shore species had higher SCPs. There was no difference in SCP between widespread high- and mid-shore species. Our results indicated that the supercooling capability is potentially an adaptative response to the local winter temperatures, and the cooling rate is a factor in determining the difference in SCP at the intraspecific and interspecific levels.

Late Miocene to Present Paleoclimatic and Paleoenvironmental Evolution of the South China Sea Recorded in the Magneto‐Cyclostratigraphy of IODP Site U1505

AbstractThe continuous sedimentary cores recovered at the International Ocean Discovery Program (IODP) Site U1505, Expedition 368, provide an opportunity for paleoceanography and paleoclimate reconstruction in the continental margin of the northern South China Sea (SCS). In this study, we conducted detailed rock‐ and paleomagnetic studies on 420 discrete samples from the top ∼200 m of the synthetic records of Holes U1505C and U1505D. Rock magnetic analyses indicate that low‐coercivity pseudosingle domain magnetite dominates as the primary ferromagnetic mineral of Site U1505. The magnetostratigraphic age model was constructed by correlating the interpreted polarity sequence with the Geomagnetic Polarity Time Scale 2020 with the constraints of the biostratigraphic data and the distribution probability of the age of each polarity zone provided by a Dynamic Time Warping algorithm. The Milankovitch cycles of the short eccentricity, obliquity, and precession cycles were identified in the magnetic susceptibility (MS) and natural gamma radiation (NGR) series based on paleomagnetic results. We established an ∼9 Myr high‐resolution astronomical time scale by tuning the MS and NGR records to the global oxygen isotope curves, the obliquity, and the eccentricity curves of the La2004 astronomical solution. Our new age model reveals detailed sedimentation rate variations and a ∼500 kyr hiatus across the Brunhes‐Matuyama boundary related to local tectonic activity. These results lay the foundation for understanding the paleoceanography and paleoclimate evolution of the SCS.

Институциональные трансформации и проекты развития Арктики и Севера: опыт экспертизы проектов человеческого развития этносоциологами Новосибирского научного центра

The article is devoted to the scientific expertise of human development projects in the North in the late Soviet and early post-Soviet periods of the institutional transformation of Russian society. Despite the fact that its official goal was the further development of the Soviet project among the peoples of the North, in essence, the researchers, in alliance with the authorities, searched for a balance between the mobilization (planned) and market strategies for the development of the Arctic and the North. The purpose of the article is to introduce into wide scientific circulation the results of research in the circumpolar zone of the RSFSR, carried out by ethnosociologists of the Novosibirsk Scientific Center (NSC) from 1982 to 1991 and later. The relevance of this work is brought to life by the desire of the state that emerged in 2010 to use market institutions in the implementation of plans for the development of the polar zone of the Russian Federation. This paper presents materials on the activities of the Regional Interdepartmental Commission for the Coordination of Comprehensive Socio-Economic, Medical, Biological and Linguistic Research on the Problems of the Development of the Peoples of the North, established in 1981 on the basis of the Siberian Branch of the USSR Academy of Sciences. The tasks and functions of the Commission are described in detail. Among the key issues of its activities were the problems of labor and employment of the peoples of Siberia, the preservation of the traditional economy and native language, mass education and access to social benefits, the development of transport infrastructure and quality housing. Although the focus of the Commission’s work remained the study of the situation of the indigenous peoples of the North and Siberia, these problems were considered in a wide range of issues of developing the national economy, gaining access to the social benefits of late socialism in the paradigm of ‘the flourishing and rapprochement of nations’. With the liquidation of the Commission in the early post-Soviet period, researchers focused on studying the consequences of radical market reforms in the interethnic communities of the North of Siberia: the archaization of everyday practices, the decline in the living standards of the population, and the revitalization of ethnic self-organization structures. It is concluded that in future ‘northern’ projects, it is necessary to combine the mobilization and market strategies for the development of the Arctic.

Relationship between soil 15N natural abundance and soil water content at global scale: Patterns and implications

Investigating the relationship between the natural abundance of soil nitrogen stable isotope (δ15N) and soil water content (SWC) in the globe can help to explain the different controls of soil δ15N in different regions, yet this was few concerned on. Based on the Craine et al. (2015) summarized soil δ15N data (https://doi.org/10.1038/srep08280), and the satellite retrieved SWC in 910 grids (size of 0.1° × 0.1°) of the globe, an upward-concave relationship between soil δ15N and SWC was observed. Higher soil δ15N existed at both the dry and wet ends (i.e., respectively below and above the intermediate range of SWC, which was about 0.20–0.30 m3/m−3(-|-)). Inconsistent relationships in five Köppen-Geiger climate zones constituted this upward-concave relationship. Positive relationship between soil δ15N and SWC in the Tropical zone determined the increasing trend of soil δ15N at the wet end in the globe. This can be explained by the increased hydrologically regulated soil N losses with the increase of SWC under the warm and moist condition. Negative relationship in the Arid zone determined the decreasing trend at the dry end in the globe. Increased abiotic N losses like ammonia volatilization and proportion of N supplement through bedrock weathering (higher δ15N) with the decrease of SWC under the dry, hot and infertile soil condition may be the main reasons. In addition, poor relationships between soil δ15N and SWC in the Temperate, Cold and Polar zones constituted the transition range of the upward-concave relationship in the globe. This reflected that not hydrologically but climatically determined low soil N losses was responsible for the low soil δ15N in these zones. These findings can help to deepen our understandings on the spatial pattern of soil δ15N and the indicated N cycle at the global scale.

High moisture confluence in Japan Sea polar air mass convergence zone captured by hourly radiosonde launches from a ship

Some of the heaviest snowfalls in urban areas in the world occur in Japan, particularly in regions that face the Japan Sea. Many heavy snowfalls are produced by a Japan Sea polar air mass convergence zone (JPCZ), which is an atmospheric river-like cloud zone that forms when Siberian cold air flows over the warm Japan Sea. Quantifying how the air–sea interaction strengthens the JPCZ is key to snowfall prediction. However, until our observations with hourly meteorological balloon launches from a training vessel in 2022, no simultaneous air–sea observations targeting the JPCZ had been conducted. Our observations showed that wind direction shifted drastically by about 90 degrees from the surface to an altitude of about 3.5 km within a narrow horizontal range of about 15 km, indicating airflow convergence from the surroundings. Maximum temperature difference between surface air (3 °C) and water was 11 °C near the JPCZ centre with 17 m s−1 wind speed. Large amounts of heat, 718 W m−2, was thus gained from the warm sea. Water vapour was also concentrated by the horizontal convergence, which caused heavy snow, equivalent to 100 cm of snowfall in 7 h. The surrounding sea greatly affects moisture formation within the JPCZ.

Spectroscopy of the interaction of cosmic plasma flows with the Earth's atmospheric aerosols

The article deals with questions about the interaction of solar plasma flows with atmospheric gas containing CDP molecules and particles. Modeling and calculations of existing electric currents and their structure were carried out. Conclusions are drawn about the effect on the structure of the current both from the side of the atmosphere and from cosmic streams of different composition. The equation of motion of a plasma with a condensed dispersed phase (CDP) in the Earth's ionosphere is considered. Conclusions are drawn about the effect of CDP on the thermal balance of plasma. It has been found that in rarefied layers of the ionosphere, plasma flows mixed with CDP are subjected to significant additional heating from CDP particles, and the lower ones serve as a heat-removing agent. Attention is drawn to the most important aspects of the results obtained in the context of their impact on the operation of power supply networks during strong solar flares. Taking into account the nature of the explosive processes that form the plasma flows from which the electric current is formed, the fluctuations of the currents inside the magnetic tubes are determined. The possible influence of these factors on the operation of the power grid line in the mountains, around the polar and equatorial zones is also considered. Such influence depends on the amplitude fluctuations of the physical parameters of the medium that forms the atmospheric currents.

AN ENIGMA OF THE PRZYBYLSKI STAR

A new scenario to explain the Przybylski star phenomenon is proposed. It is based on the supposition that this star is a component of a binary system with a neutron star (similar to the hypothesis proposed earlier by Gopka, Ul’yanov & Andrievskii). The main difference with previous scenario is as following. The orbits of the stars of this system lie in the plane of the sky (or very close to this plane). Thus, we see this star (and its companion) nearly polar-on, and therefore we cannot detect the orbital motion (spectral line based) from the Przybylski star spectrum. In relation to the Przybylski star, the neutron star is a γ-ray pulsar for it. A neutron star is a source of relativistic particles and radiation emitted from the certain parts of its surface. The topology of this radiation strongly depends on the the magnetic field configuration of the neutron star. Existing models suppose that 1) high-energy electronpositron pairs and hard radiation are produced in the (magnetic) polar zones. Accelerated charge particles that move along magnetic lines emit electromagnetic quanta. In this model the radio-emission is genetically linked with the emission of the γ-quanta. 2) Another model of the outer gap is based on the assumption that there is a vacuum gap in the outer magnetosphere of the neutron star, which arises due to the constant escape of charged particles through the light cylinder along the open magnetic field lines. The direction of such escape may be roughly orthogonal to the rotation axis. If the rotational axes of the Przybylski star and the neutron star are close in direction (or even aligned), charged particles and hard radiation ejected in the approximately orthogonal direction at a large solid angle can enter the Przybylski star atmosphere, causing there different physical processes. As a possible source of the free neutrons could be the nuclear reactions between high-energy γ-quanta and nuclei of some atoms in the Przybylski star atmosphere gas. As a result, photoneutrons can be generated. Large enough neutron flux can be produced in the reactions with quite abundant element of the atmosphere gas (for example, helium). The photoneutrons produced in these reactions are rapidly thermalized and, as resonant neutrons, react with seed nuclei in the s-process. It should be also noted that together with s-process elements, the deuterium nuclei could be formed as a result of the interactions of the free resonant neutrons with the hydrogen atoms, but this issue has not yet been worked out.

Spatial and temporal variation and distribution of mesozooplankton in the Drake Passage sampled with the continuous Plankton Recorder

Zooplankton is the main link between primary producers and higher trophic levels in marine foods webs. In the Southern Ocean, zooplankton could be key in identifying environmental changes, given rapid warming registered in the area in the last decades. The Drake Passage is a choke point of oceanographic processes, since it is the narrowest and most dynamic path of the Antarctic Circumpolar Current (ACC). The objective of this study was to determine the horizontal spatial variations of mesozooplankton in the Drake Passage relative to Southern Ocean oceanographic fronts and zones. Three transects were sampled using a CPR in the Drake Passage during the austral summer of 2009 and 2010. Temperature and salinity were measured at 1-min intervals with a thermosalinograph and Chlorophyll a data extracted from NASA's ocean color web. Organisms were counted and identified to the lowest level, resulting in 53 taxa, with 24 identified to species, eight to genus and 21 to a higher taxonomic level. Four fronts (Subantarctic Front - SAF, Polar Front - PF, South of ACC Front - SACCF and Peninsula Front -PF*) delimiting five zones (Subantarctic Zone - SAZ, Polar Front Zone - PFZ, Antarctic Zone - AZ, Southern Zone - SZ and Transitional Water Zone with Bellingshausen Sea Influence TBW) were registered according to temperature values. Higher mesozooplankton abundances were recorded in the PFZ (412.0 ± 27.9 ind. m−3) in 2009 and in the AZ (128 ± 12.3 ind. m−3) during 2010. Copepoda were the most abundant group (82%), followed by crustacean eggs (4.3%) and Larvacea (4.0%). Within Copepoda, the most abundant taxa were Calanidae copepodites (33.5 ± 53.4 ind. m−3), Oithona spp. (25.4 ± 27.1 ind. m−3) and Calanus simillimus (19.4 ± 26.1 ind. m−3). Differences in community structure were found between zones with C. simillimus and Thysanoessa macrura contributing most to the dissimilarities between the SAZ and the PFZ, Ctenocalanus citer between the PFZ and AZ, Euphausia superba between zones south of the Polar Front and Salpa thompsoni between the SZ and TBW. Some species or taxa are related to or: indicators of a particular zone. The PFZ was the most diverse and had higher mesozooplankton abundances compared to the other zones. Changes in composition are perceptible compared to previous studies, with a decrease of larger organisms and richness, lack of larger copepods, decrease of krill and increase of S. thompsoni abundances.

A regional-scale approach for modeling primary production and biogenic silica export in the Southern Ocean

Persistent uncertainties in the representations of net primary production (NPP) and silicate in the Southern Ocean have been noted in recent assessments ofthe ocean biogeochemical components of Earth system models (ESMs). Consequently, more mechanistic studies at the regional scale are required. To reduce these uncertainties, we applied a one-dimensional (1D) marine ecosystem model to different bioregions in the Southern Ocean: the Polar Frontal Zone in the Pacific sector, the seasonal sea ice zone in the northwestern Ross Sea, and the inner shelf of Terra Nova Bay. To make the existing ecosystem model applicable to the Southern Ocean, we modified the phytoplankton physiology (stoichiometry depending on species) and the silicate cycle (dissolution rate of biogenic silica (BSi) depending on latitude) in the model. We quantified and compared seasonal variations in several limitation factors of NPP, namely, iron, irradiance, silicate and temperature, in the three regions. The simulation results showed that dissolved iron plays the most significant role in determining the magnitude of NPP and the phytoplankton community structure during summer. Additionally, the modified model successfully reproduced the vertical flux of BSi and particulate organic carbon (POC). The POC export efficiency was high in the inner shelf zone, which had high levels of iron concentration, NPP, and Phaeocystis biomass. In contrast, BSi export occurred most efficiently in the Polar Frontal Zone, where diatoms are dominant, the BSi dissolution rate is low, and NPP is extremely low. Our results from the integrated mechanistic framework at the regional scale demonstrate which specific processes should be urgently included in ESMs for better representation of the biogeochemical dynamics in the Southern Ocean.

The Impact of a Southern Ocean Cyclonic Eddy on Mesopelagic Micronekton

AbstractMesoscale eddies shape the foraging ecology of predators such as marine mammals and seabirds. A growing number of animal tracking studies show that predators alter their swimming, diving, and foraging behavior within mesoscale eddies. However, little is known about how Southern Ocean eddies influence the distribution of mesopelagic micronekton (fish, squid, and crustaceans), which are major prey items of megafauna. Studies in other oceanic regions have found that eddies can influence the abundance and community composition of micronekton. Here, we analyze acoustic observations from a 14‐day survey of a cyclonic mesoscale eddy, its surrounding waters, and the Polar Frontal Zone (PFZ) waters where the eddy formed. We report and interpret spatial patterns of acoustic backscatter at 18 and 75 kHz, proxies indicating combined changes in species, size, and abundance of micronekton. We find that the vertical distribution of acoustic backscatter matched the underwater light conditions characteristic of the eddy core, periphery, and surrounding waters, at scales smaller than 10 km. The median water‐column integrated acoustic backscatter values in the eddy core were only half of those measured in the Sub‐Antarctic Zone waters surrounding the eddy, but similar to those measured in the PFZ, where the eddy originated 27 days prior. These results suggest that, as for physical and chemical tracers, the eddy maintained its biological characteristics from its source waters creating a unique habitat compared to its surroundings.

Detecting the Greatest Changes in Global Satellite-Based Precipitation Observations

In recent years, the analysis of abrupt and non-abrupt changes in precipitation has received much attention due to the importance of climate change-related issues (e.g., extreme climate events). In this study, we used a novel segmentation algorithm, DBEST (Detecting Breakpoints and Estimating Segments in Trend), to analyze the greatest changes in precipitation using a monthly pixel-based satellite precipitation dataset (TRMM 3B43) at three different scales: (i) global, (ii) continental, and (iii) climate zone, during the 1998–2019 period. We found significant breakpoints, 14.1%, both in the form of abrupt and non-abrupt changes, in the global scale precipitation at the 0.05 significance level. Most of the abrupt changes were observed near the Equator in the Pacific Ocean and Asian continent, relative to the rest of the globe. Most detected breakpoints occurred during the 1998–1999 and 2009–2011 periods on the global scale. The average precipitation change for the detected breakpoint was ±100 mm, with some regions reaching ±3000 mm. For instance, most portions of northern Africa and Asia experienced major changes of approximately +100 mm. In contrast, most of the South Pacific and South Atlantic Ocean experienced changes of −100 mm during the studied period. Our findings indicated that the larger areas of Africa (23.9%), Asia (22.9%), and Australia (15.4%) experienced significant precipitation breakpoints compared to North America (11.6%), South America (9.3%), Europe (8.3%), and Oceania (9.6%). Furthermore, we found that the majority of detected significant breakpoints occurred in the arid (31.6%) and polar (24.1%) climate zones, while the least significant breakpoints were found for snow-covered (11.5%), equatorial (7.5%), and warm temperate (7.7%) climate zones. Positive breakpoints’ temporal coverage in the arid (54.0%) and equatorial (51.9%) climates were more than those in other climates zones. Here, the findings indicated that large areas of Africa and Asia experienced significant changes in precipitation (−250 to +250 mm). Compared to the average state (trend during a specific period), the greatest changes in precipitation were more abrupt and unpredictable, which might impose a severe threat to the ecology, environment, and natural resources.

Specific resonance mode enhancement and suppression using non-uniform polarization of piezoelectric wafers: Theory and experiments

We present experimental demonstration of specific resonance mode enhancement and suppression in circular and rectangular piezoelectric wafers with engineered non-uniform polarization profiles. The polarization profiles are designed based on the electromechanical impedance response of non-uniformly polarized wafers as obtained from the theory. The circular wafers are fabricated with non-uniform polarization profiles that involve a central polarized region surrounded by an unpolarized region. The radius of the polarization zone is designed based on the condition for specific mode enhancement obtained from the electromechanical impedance response of non-uniformly polarized wafers. We actually show how the condition can not only be used to enhance but also to suppress electromechanical resonances. Two kinds of wafers are designed and fabricated to specifically suppress second and third radial modes respectively. Similarly, rectangular wafers are designed with two different kinds of non-uniform polarization profiles — the first of which enhances the second in-plane extensional mode in the impedance spectrum and the second polarization profile suppresses all the electromechanical resonances pertaining to the in-plane extensional modes and selectively excites only the in-plane bending modes. The proposed approach of using non-uniformly polarized wafers finds application in designing multi-frequency sensors/transducers, frequency-tuned receivers, acoustic beamforming, and other non-traditional applications such as information storage.