This research marks the first comprehensive structural analysis of the Instekleppane outcrop, located in the western part of the Lützow-Holm Complex (LHC), a Neoproterozoic-Cambrian high-grade metamorphic terrane, East Antarctica. The ∼1 km2 outcrop, situated southwest of Syowa Station and east of Shirase Glacier, was investigated as part of the 65th Japanese Antarctic Research Expedition (JARE-65). The lithological assemblage includes felsic orthopyroxene-biotite gneiss, garnet-bearing felsic granulite, Mg-Al-rich gneiss, mafic hornblende-orthopyroxene-clinopyroxene granulite, ultramafic rocks, and minor granitic intrusions. Six stages of deformation (D0–D5) were identified, of which four (D0 to D3) are considered as major events. D0 corresponds to the development of primary sedimentary or magmatic layering and D1 corresponds to initial foliation development. While D2 is characterized by earlier layer parallel stretching and the formation of B21 mafic boudins followed by two folding phases: F21 (recumbent, isoclinal, intrafolial folds) and F22 (overturned folds), both with E–W trending axial planes. D3 is marked by upright to plunging open folds (F3) with NW–SE axial planes. D4 corresponds to reverse shear zones, and D5 involves strike-slip shear zones. The deformation history at the Instekleppane shares similarities with nearby high-grade terranes such as Rundvågshetta and Langhovde, suggest a regionally consistent ductile deformation history within the LHC during its tectonic evolution.
{"title":"Structural evolution of the Instekleppane, Lützow-Holm Complex: Deformation patterns in high-grade zones of east Antarctica","authors":"Lakshmanan Sreehari , Tatsuro Adachi , Yuki Mori , Tomokazu Hokada","doi":"10.1016/j.polar.2025.101249","DOIUrl":"10.1016/j.polar.2025.101249","url":null,"abstract":"<div><div><span><span>This research marks the first comprehensive structural analysis of the Instekleppane outcrop, located in the western part of the Lützow-Holm Complex (LHC), a Neoproterozoic-Cambrian high-grade metamorphic terrane, East </span>Antarctica. The ∼1 km</span><sup>2</sup><span><span><span> outcrop, situated southwest of Syowa Station and east of Shirase Glacier, was investigated as part of the 65th Japanese Antarctic Research Expedition (JARE-65). The lithological assemblage includes felsic orthopyroxene-biotite gneiss, garnet-bearing felsic </span>granulite, Mg-Al-rich gneiss, mafic hornblende-orthopyroxene-clinopyroxene granulite, </span>ultramafic rocks, and minor granitic intrusions. Six stages of deformation (D</span><sub>0</sub>–D<sub>5</sub>) were identified, of which four (D<sub>0</sub> to D<sub>3</sub>) are considered as major events. D<sub>0</sub> corresponds to the development of primary sedimentary or magmatic layering and D<sub>1</sub> corresponds to initial foliation development. While D<sub>2</sub> is characterized by earlier layer parallel stretching and the formation of B<sub>21</sub> mafic boudins followed by two folding phases: F<sub>21</sub> (recumbent, isoclinal, intrafolial folds) and F<sub>22</sub> (overturned folds), both with E–W trending axial planes. D<sub>3</sub> is marked by upright to plunging open folds (F<sub>3</sub>) with NW–SE axial planes. D<sub>4</sub> corresponds to reverse shear zones, and D<sub>5</sub><span> involves strike-slip shear zones. The deformation history<span><span> at the Instekleppane shares similarities with nearby high-grade terranes such as Rundvågshetta and Langhovde, suggest a regionally consistent ductile deformation history within the LHC during its </span>tectonic evolution.</span></span></div></div>","PeriodicalId":20316,"journal":{"name":"Polar Science","volume":"46 ","pages":"Article 101249"},"PeriodicalIF":2.0,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145739148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01Epub Date: 2025-08-05DOI: 10.1016/j.polar.2025.101259
Aswathy Shaji , Anu Gopinath , Midhun Shah Hussain , Sabu Prabhakaran , K. Anoop Krishnan
This study focuses on the speciation of metals (Cr, Mn, Fe, Ni, Cu, Zn) in the surface sediments collected from Arctic fjords and lakes as part of the India Expedition to Arctic during the years 2018 and 2019. The speciation studies were performed focusing on five fractions, namely, exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter and residual metal. The sedimentary characteristics like pH, TOC and elemental concentrations were also studied to understand the role of these parameters in affecting the metal distribution in different fraction within the sediments. Different risk indices like, Risk Assessment Code (RAC), modified RAC, Individual Contamination Factor (ICF) and Global Contamination Factor (GCF) were also evaluated to find out the threats posed by these contaminates in this pristine environment. The various risk assessment of the metals under study reveals the presence of a low to moderate contamination prevailing in the system.
{"title":"Metal speciation in the surface sediments of an Arctic fjord and nearby lakes","authors":"Aswathy Shaji , Anu Gopinath , Midhun Shah Hussain , Sabu Prabhakaran , K. Anoop Krishnan","doi":"10.1016/j.polar.2025.101259","DOIUrl":"10.1016/j.polar.2025.101259","url":null,"abstract":"<div><div>This study focuses on the speciation of metals (Cr, Mn, Fe, Ni, Cu, Zn) in the surface sediments collected from Arctic fjords and lakes as part of the India Expedition to Arctic during the years 2018 and 2019. The speciation studies were performed focusing on five fractions, namely, exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter and residual metal. The sedimentary characteristics like pH, TOC and elemental concentrations were also studied to understand the role of these parameters in affecting the metal distribution in different fraction within the sediments. Different risk indices like, Risk Assessment Code (RAC), modified RAC, Individual Contamination Factor (ICF) and Global Contamination Factor (GCF) were also evaluated to find out the threats posed by these contaminates in this pristine environment. The various risk assessment of the metals under study reveals the presence of a low to moderate contamination prevailing in the system.</div></div>","PeriodicalId":20316,"journal":{"name":"Polar Science","volume":"46 ","pages":"Article 101259"},"PeriodicalIF":2.0,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145739194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01Epub Date: 2025-07-08DOI: 10.1016/j.polar.2025.101255
Kohei Sumiya , Dai Sumiyoshi , Kazutoshi Sato , Akihiko Murata , Shigeto Nishino , Kohei Matsuno
Sea ice in the Pacific Arctic Ocean has been rapidly decreasing over recent decades. However, knowledge of its effects on microplankton is limited. To elucidate the effect of sea ice reduction on the microplankton community of the Pacific Arctic Ocean, we examined the differences in the microplankton community and hydrography between 2019 and 2020. Based on the cluster analysis, the microplankton community was divided into six groups. In the southern Chukchi Sea, high cell densities were observed with high variability in group occurrence owing to the inflow of nutrient-rich Pacific water. In the northern Chukchi Sea, a 1-month inter-annual difference in sea ice melting timing induced changes in the microplankton community through hydrographical changes. Early sea ice melting stimulates the growth of phytoplankton species (Proboscia alata), which can utilize organic nitrogen compounds. In the marginal ice zone, a 10-day inter-annual difference in sea ice melting was observed, resulting in variations in hydrographic conditions; however, these changes did not affect the microplankton community. Our findings indicate that microplankton production and diversity respond differently to sea ice melting in varies by region in the Pacific Arctic Ocean.
{"title":"Influence of early sea ice melting on the autumn microplankton community of the Pacific Arctic Ocean","authors":"Kohei Sumiya , Dai Sumiyoshi , Kazutoshi Sato , Akihiko Murata , Shigeto Nishino , Kohei Matsuno","doi":"10.1016/j.polar.2025.101255","DOIUrl":"10.1016/j.polar.2025.101255","url":null,"abstract":"<div><div>Sea ice in the Pacific Arctic Ocean has been rapidly decreasing over recent decades. However, knowledge of its effects on microplankton is limited. To elucidate the effect of sea ice reduction on the microplankton community of the Pacific Arctic Ocean, we examined the differences in the microplankton community and hydrography between 2019 and 2020. Based on the cluster analysis, the microplankton community was divided into six groups. In the southern Chukchi Sea, high cell densities were observed with high variability in group occurrence owing to the inflow of nutrient-rich Pacific water. In the northern Chukchi Sea, a 1-month inter-annual difference in sea ice melting timing induced changes in the microplankton community through hydrographical changes. Early sea ice melting stimulates the growth of phytoplankton species (<em>Proboscia alata</em>), which can utilize organic nitrogen compounds. In the marginal ice zone, a 10-day inter-annual difference in sea ice melting was observed, resulting in variations in hydrographic conditions; however, these changes did not affect the microplankton community. Our findings indicate that microplankton production and diversity respond differently to sea ice melting in varies by region in the Pacific Arctic Ocean.</div></div>","PeriodicalId":20316,"journal":{"name":"Polar Science","volume":"46 ","pages":"Article 101255"},"PeriodicalIF":2.0,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145739073","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The first comprehensive multi-day geological survey was conducted at Instekleppane in the southern part of the Lützow-Holm Complex, East Antarctica, by the 65th Japanese Antarctic Research Expedition (JARE65). This exposure is predominantly composed of felsic orthopyroxene-biotite gneiss, leucocratic garnet-biotite gneiss, granitic biotite gneiss, and felsic garnet-orthopyroxene-biotite gneiss with intercalations of mafic granulites, meta-ultramafic rocks, and Mg–Al-rich rocks. Several Mg–Al-rich rocks, such as sapphirine-cordierite-biotite gneiss and garnet-sapphirine-orthopyroxene-cordierite gneiss, have reaction textures indicating decompression under ultrahigh-temperature (UHT) conditions. Similar lithological relations and metamorphic signatures have been reported from Rundvågshetta, suggesting a possible geological linkage between these exposures.
{"title":"High-grade metamorphic rocks in Instekleppane, Lützow-Holm Complex, east Antarctica: A potential new locality of ultrahigh-temperature (UHT) metamorphic rocks","authors":"Tatsuro Adachi , Lakshmanan Sreehari , Yuki Mori , Tomokazu Hokada","doi":"10.1016/j.polar.2025.101263","DOIUrl":"10.1016/j.polar.2025.101263","url":null,"abstract":"<div><div>The first comprehensive multi-day geological survey was conducted at Instekleppane in the southern part of the Lützow-Holm Complex, East Antarctica, by the 65th Japanese Antarctic Research Expedition (JARE65). This exposure is predominantly composed of felsic orthopyroxene-biotite gneiss, leucocratic garnet-biotite gneiss, granitic biotite gneiss, and felsic garnet-orthopyroxene-biotite gneiss with intercalations of mafic granulites, meta-ultramafic rocks, and Mg–Al-rich rocks. Several Mg–Al-rich rocks, such as sapphirine-cordierite-biotite gneiss and garnet-sapphirine-orthopyroxene-cordierite gneiss, have reaction textures indicating decompression under ultrahigh-temperature (UHT) conditions. Similar lithological relations and metamorphic signatures have been reported from Rundvågshetta, suggesting a possible geological linkage between these exposures.</div></div>","PeriodicalId":20316,"journal":{"name":"Polar Science","volume":"46 ","pages":"Article 101263"},"PeriodicalIF":2.0,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145739149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01Epub Date: 2025-06-21DOI: 10.1016/j.polar.2025.101250
E.O. Dubinina , Ju.N. Chizhova
The isotope (δ18O and δ2H) variations in river waters are averaged in the river plume zones during their residence at the Arctic shelf. We demonstrate that the residence time (τ) of river waters on the Arctic shelf can be estimated using the sinusoidal modelling of stable isotope (δ18О, δ2H) composition of the freshwater component (FC) in river plumes. The plume zones of six Siberian rivers the Ob, Yenisei, Khatanga, Lena, Indigirka and Kolyma were sampled during the summer period in 2015–2017. The τ value of waters of the Ob, Yenisei, Lena, and Kolyma rivers were calculated using sinusoidal model and seasonal δ18О and δ2Н data for these rivers extracted from the Arctic GRO dataset. The calculated τ-values for the Yenisei and Ob plumes are maximal (τ = 4.3–5.5 months), while for the Lena and Kolyma plumes, the τ value is almost twice as low (2–3 months). These estimations show that spring continental waters are present within the river plumes at the end of ice-free season. Based on the FC isotope composition and τ values obtained for river plumes, the general geographic pattern of isotope signatures of summer continental runoff entering the Arctic shelf can be considered as a result of the continental effect of winter precipitation. The δ18О(FC) and δ2H(FC) relationship of averaged data obtained for summer runoff for studied Siberian rivers show absence of the evaporation effect and close to the Global Meteoric Waters line: δ2Н = 8.12(±0.42) × δ18О + 8.6(±7.9).
{"title":"Isotope (δ18O, δ2H) signature of river and plume waters: Residence time of summer Siberian river runoff on the East Arctic shelf","authors":"E.O. Dubinina , Ju.N. Chizhova","doi":"10.1016/j.polar.2025.101250","DOIUrl":"10.1016/j.polar.2025.101250","url":null,"abstract":"<div><div>The isotope (δ<sup>18</sup>O and δ<sup>2</sup><span><span>H) variations in river waters are averaged in the </span>river plume<span> zones during their residence at the Arctic shelf. We demonstrate that the residence time (τ) of river waters on the Arctic shelf can be estimated using the sinusoidal modelling of stable isotope (δ</span></span><sup>18</sup>О, δ<sup>2</sup>H) composition of the freshwater component (FC) in river plumes. The plume zones of six Siberian rivers the Ob, Yenisei, Khatanga, Lena, Indigirka and Kolyma were sampled during the summer period in 2015–2017. The τ value of waters of the Ob, Yenisei, Lena, and Kolyma rivers were calculated using sinusoidal model and seasonal δ<sup>18</sup>О and δ<sup>2</sup>Н data for these rivers extracted from the Arctic GRO dataset. The calculated τ-values for the Yenisei and Ob plumes are maximal (τ = 4.3–5.5 months), while for the Lena and Kolyma plumes, the τ value is almost twice as low (2–3 months). These estimations show that spring continental waters are present within the river plumes at the end of ice-free season. Based on the FC isotope composition and τ values obtained for river plumes, the general geographic pattern of isotope signatures of summer continental runoff entering the Arctic shelf can be considered as a result of the continental effect of winter precipitation. The δ<sup>18</sup>О(FC) and δ<sup>2</sup><span>H(FC) relationship of averaged data obtained for summer runoff for studied Siberian rivers show absence of the evaporation effect and close to the Global Meteoric Waters line: δ</span><sup>2</sup>Н = 8.12(±0.42) × δ<sup>18</sup>О + 8.6(±7.9).</div></div>","PeriodicalId":20316,"journal":{"name":"Polar Science","volume":"46 ","pages":"Article 101250"},"PeriodicalIF":2.0,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145739195","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01Epub Date: 2025-10-24DOI: 10.1016/j.polar.2025.101302
Y. Hiroi , T. Hokada , N. Furukawa , T. Adachi , B. Prame , L.R.K. Perera , M. Satish-Kumar , Y. Motoyoshi
The garnetiferous granulite in central Sri Lanka contains more than 27 minerals with various textures and compositions. The garnet + orthopyroxene + biotite + plagioclase + quartz + ilmenite + rutile + pyrrhotite + melt assemblage may have been stable at the metamorphic peak. The estimated peak P–T conditions are >0.6 GPa and >800 °C. Garnet occurs as anhedral porphyroblasts up to 1 cm in diameter. Some grains contain numerous inclusions, including melt inclusions (felsite–nanogranite inclusions, or FNIs), while others are free of inclusion except for fine–grained ilmenite and rutile. They commonly exhibit compositional zoning, with Mg decreasing and Ca increasing towards the margin. Some grains exhibit P zoning and are divided into P–poor core, P–rich mantle and P–poor rim. In the P–rich mantle, the FNIs are surrounded by areas of P depletion, indicating FNIs’ strong effect on the behavior of P in garnet. Grandidierite exclusively occurs in FNIs. Cathodoluminescence imaging revealed "hidden" dendritic high–quartz within anhedral quartz grains in FNIs. Dynamic crystallization experiments reproduced the characteristic texture. Plagioclase and biotite exhibit extremely wide compositional variations depending on their occurrence mode. Zoned carbonate and moganite–containing chalcedony occur as inclusions in garnet in places. These features all resulted from high–temperature metamorphism followed by the complex cooling history experienced by the rocks in a crustal–scale suture zone.
{"title":"Hidden dendritic high quartz, grandidierite, euhedrally zoned Mg–Fe carbonate and chalcedony in garnet; documentation and significance of multi–stage recrystallization of garnetiferous granulite from central Sri Lanka during rapid cooling","authors":"Y. Hiroi , T. Hokada , N. Furukawa , T. Adachi , B. Prame , L.R.K. Perera , M. Satish-Kumar , Y. Motoyoshi","doi":"10.1016/j.polar.2025.101302","DOIUrl":"10.1016/j.polar.2025.101302","url":null,"abstract":"<div><div>The garnetiferous granulite in central Sri Lanka contains more than 27 minerals with various textures and compositions. The garnet + orthopyroxene + biotite + plagioclase + quartz + ilmenite + rutile + pyrrhotite + melt assemblage may have been stable at the metamorphic peak. The estimated peak <em>P–T</em> conditions are >0.6 GPa and >800 °C. Garnet occurs as anhedral porphyroblasts up to 1 cm in diameter. Some grains contain numerous inclusions, including melt inclusions (felsite–nanogranite inclusions, or FNIs), while others are free of inclusion except for fine–grained ilmenite and rutile. They commonly exhibit compositional zoning, with Mg decreasing and Ca increasing towards the margin. Some grains exhibit P zoning and are divided into P–poor core, P–rich mantle and P–poor rim. In the P–rich mantle, the FNIs are surrounded by areas of P depletion, indicating FNIs’ strong effect on the behavior of P in garnet. Grandidierite exclusively occurs in FNIs. Cathodoluminescence imaging revealed \"hidden\" dendritic high–quartz within anhedral quartz grains in FNIs. Dynamic crystallization experiments reproduced the characteristic texture. Plagioclase and biotite exhibit extremely wide compositional variations depending on their occurrence mode. Zoned carbonate and moganite–containing chalcedony occur as inclusions in garnet in places. These features all resulted from high–temperature metamorphism followed by the complex cooling history experienced by the rocks in a crustal–scale suture zone.</div></div>","PeriodicalId":20316,"journal":{"name":"Polar Science","volume":"46 ","pages":"Article 101302"},"PeriodicalIF":2.0,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145739092","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mode of occurrence of fracture-filling microcrystalline quartz-Al2SiO5 mineral assemblage is examined in the Sør Rondane Mountains (SRM), East Antarctica. The microcrystalline Al2SiO5 minerals characteristically represent fibrous texture and are identified to be kyanite and sillimanite by Raman spectroscopy. Pelitic gneisses containing such fractures are observed in a wide area of over 50 km in the SRM. The microcrystalline quartz-Al2SiO5 mineral assemblage can be formed by acidic aqueous fluid infiltration which removed alkali and alkaline-earth metals in feldspars and cordierite. Such fluid infiltrations possibly took place during exhumation stage at < ca. 560 Ma.
{"title":"Mode of occurrence of fracture-filling microcrystalline quartz and Al2SiO5 mineral assemblage in the Sør Rondane Mountains, East Antarctica: Implication for fluid infiltration during retrograde metamorphism","authors":"Fumiko Higashino , Tetsuo Kawakami , Hayato Ikeda , Tatsuro Adachi , Masaoki Uno","doi":"10.1016/j.polar.2025.101209","DOIUrl":"10.1016/j.polar.2025.101209","url":null,"abstract":"<div><div>Mode of occurrence of fracture-filling microcrystalline quartz-Al<sub>2</sub>SiO<sub>5</sub><span> mineral assemblage is examined in the Sør Rondane Mountains (SRM), East Antarctica. The microcrystalline Al</span><sub>2</sub>SiO<sub>5</sub><span> minerals characteristically represent fibrous texture and are identified to be kyanite and sillimanite by Raman spectroscopy. Pelitic gneisses containing such fractures are observed in a wide area of over 50 km in the SRM. The microcrystalline quartz-Al</span><sub>2</sub>SiO<sub>5</sub><span> mineral assemblage can be formed by acidic aqueous fluid infiltration which removed alkali and alkaline-earth metals in feldspars and cordierite. Such fluid infiltrations possibly took place during exhumation stage at < ca. 560 Ma.</span></div></div>","PeriodicalId":20316,"journal":{"name":"Polar Science","volume":"46 ","pages":"Article 101209"},"PeriodicalIF":2.0,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145739093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01Epub Date: 2025-05-31DOI: 10.1016/j.polar.2025.101215
Takenobu Toyota , Yuriko Arihara , Takuji Waseda , Masato Ito , Jun Nishioka
In the marginal ice zone, sea ice melts by absorbing heat from the surrounding seawater. Given that for the same sea ice area, total perimeter is longer for smaller ice floes, the information on floe size distribution is essential to predict the melting rate of sea ice. Our study was conducted in the southern Sea of Okhotsk under relatively calm and warm conditions in mid-February 2020. For the first time we used a drone to measure ice floes at a scale of less than a few meters and deduce the melting processes. Our results revealed that the cumulative floe size distribution is represented well by the power law with an exponent of 1.51 for floes larger than 0.9 m, and that each floe geometry has self-similar properties with an aspect ratio of 1.73. For floes below 0.9 m, it was shown that the floe size distribution deviates somewhat from the power law, associated with thermodynamic breakup which is caused by the increase in sea ice porosity. The surface heat budget analysis using the meteorological reanalysis datasets suggests that the efficient heat absorption from the open water and internal melting contributed to this process.
{"title":"Melting processes of the marginal ice zone inferred from floe size distributions measured with a drone in the southern Sea of Okhotsk","authors":"Takenobu Toyota , Yuriko Arihara , Takuji Waseda , Masato Ito , Jun Nishioka","doi":"10.1016/j.polar.2025.101215","DOIUrl":"10.1016/j.polar.2025.101215","url":null,"abstract":"<div><div>In the marginal ice zone, sea ice melts by absorbing heat from the surrounding seawater. Given that for the same sea ice area, total perimeter is longer for smaller ice floes, the information on floe size distribution is essential to predict the melting rate of sea ice. Our study was conducted in the southern Sea of Okhotsk under relatively calm and warm conditions in mid-February 2020. For the first time we used a drone to measure ice floes at a scale of less than a few meters and deduce the melting processes. Our results revealed that the cumulative floe size distribution is represented well by the power law with an exponent of 1.51 for floes larger than 0.9 m, and that each floe geometry has self-similar properties with an aspect ratio of 1.73. For floes below 0.9 m, it was shown that the floe size distribution deviates somewhat from the power law, associated with thermodynamic breakup which is caused by the increase in sea ice porosity. The surface heat budget analysis using the meteorological reanalysis datasets suggests that the efficient heat absorption from the open water and internal melting contributed to this process.</div></div>","PeriodicalId":20316,"journal":{"name":"Polar Science","volume":"46 ","pages":"Article 101215"},"PeriodicalIF":2.0,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145739057","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01Epub Date: 2025-10-30DOI: 10.1016/j.polar.2025.101305
G.H. Grantham , T. Spell , M.W. Knoper , P. le Roux
The Straumsvola Alkaline Complex in H.U. Sverdrupfjella, western Dronning Maud Land, Antarctica (WDML) consists of four units comprising a Central Layered Zone (CLZ), a Central Outer Zone (COZ), a Mesocratic Zone (MZ) and Mafic layer (ML). The COZ is intruded by the CLZ and MZ. Layering and textures in the CLZ reflect fractionation of cumulate perthite and nepheline with intercumulate liquid from which amphibole, biotite and clinopyroxene crystallised. Amphibole, biotite and clinopyroxene locally form spherical nodules with interdigitating feldspar laths. The ML is included as part of the CLZ, suggested by similar field characteristics and chemical data. Similar textures reflecting early feldspar crystallisation with later intercumulate amphibole, biotite clinopyroxene are seen in all units. The chemical data of the felsic and mafic components don't show linear relationships suggestive of disequilibrium between the mineral assemblages and that they may have formed by liquid immiscibility. The ML is inferred to have formed from expulsion of intercumulate mafic magma through the permeable CLZ upwards by compaction of the felsic cumulates. Isotope data indicate the alkaline rocks are mantle derived, similar to dykes of similar age and vicinity. 40Ar/39Ar dates provide ages of ca. 178 Ma for the complex. Whole rock compositions of the alkaline rocks, combined with mineral and Jurassic dyke compositions plot in separate compositional fields, consistent with liquid immiscibility experiments and natural examples. Alternatively contrasting mantle melting would be required in the genesis of these rocks to produce synchronous peralkaline and tholeiitic melts in the same localities, combined with fractional crystallization.
{"title":"The geology, chemistry and age of the Straumsvola Alkaline Complex, western Dronning Maud Land, Antarctica. The role of liquid immiscibility","authors":"G.H. Grantham , T. Spell , M.W. Knoper , P. le Roux","doi":"10.1016/j.polar.2025.101305","DOIUrl":"10.1016/j.polar.2025.101305","url":null,"abstract":"<div><div>The Straumsvola Alkaline Complex in H.U. Sverdrupfjella, western Dronning Maud Land, Antarctica (WDML) consists of four units comprising a Central Layered Zone (CLZ), a Central Outer Zone (COZ)<em>,</em> a Mesocratic Zone (MZ) and Mafic layer (ML). The COZ is intruded by the CLZ and MZ. Layering and textures in the CLZ reflect fractionation of cumulate perthite and nepheline with intercumulate liquid from which amphibole, biotite and clinopyroxene crystallised. Amphibole, biotite and clinopyroxene locally form spherical nodules with interdigitating feldspar laths. The ML is included as part of the CLZ, suggested by similar field characteristics and chemical data. Similar textures reflecting early feldspar crystallisation with later intercumulate amphibole, biotite clinopyroxene are seen in all units. The chemical data of the felsic and mafic components don't show linear relationships suggestive of disequilibrium between the mineral assemblages and that they may have formed by liquid immiscibility. The ML is inferred to have formed from expulsion of intercumulate mafic magma through the permeable CLZ upwards by compaction of the felsic cumulates. Isotope data indicate the alkaline rocks are mantle derived, similar to dykes of similar age and vicinity. <sup>40</sup>Ar/<sup>39</sup>Ar dates provide ages of ca. 178 Ma for the complex. Whole rock compositions of the alkaline rocks, combined with mineral and Jurassic dyke compositions plot in separate compositional fields, consistent with liquid immiscibility experiments and natural examples. Alternatively contrasting mantle melting would be required in the genesis of these rocks to produce synchronous peralkaline and tholeiitic melts in the same localities, combined with fractional crystallization.</div></div>","PeriodicalId":20316,"journal":{"name":"Polar Science","volume":"46 ","pages":"Article 101305"},"PeriodicalIF":2.0,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145739055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01Epub Date: 2025-05-11DOI: 10.1016/j.polar.2025.101212
Esra Günaydın , Mahmut Oğuz Selbesoğlu , Mustafa Fahri Karabulut , Işıl Erdoğdu , Beyza Nur Kılıç , Bahadır Çelik , Özgün Oktar , Burcu Özsoy
The Earth's atmosphere is a system that significantly influences weather patterns and climate by regulating the radiation balance. Disturbances in the balance of incoming and reflected radiation filtered through the atmosphere constitute an interaction driving the planet's temperature, atmospheric circulation, and climate mechanism. The polar regions play a crucial role in maintaining the global climate balance due to their influence on atmospheric circulation patterns. In this context, monitoring atmospheric variables and their changes over time is critical for understanding and predicting global climate change. This study investigated the long-term variations of aerosol optical depth (AOD) in Antarctica, a region highly sensitive to atmospheric changes. The research utilized Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua and Terra AOD products across three different-sized areas. The temporal variations of AOD over a twenty-year period were examined on a spatial basis to understand the patterns and trends of AOD. Furthermore, a comparison was conducted using data from the Marambio Aerosol Robotic Network (AERONET) station and satellite-based data. The evaluations were carried out separately using data from the Terra and Aqua satellites, and similar increasing trends in AOD values were observed for both datasets from 2002 to 2022. The correlation between the four-month mean AOD of Aqua and AERONET, as well as Terra and AERONET, was calculated as 0.6488 and 0.6190, respectively. A Seasonal Autoregressive Integrated Moving Average (SARIMA) model was applied to satellite-based data to predict the dataset's behavior in the near future. The predictive analysis based on these datasets indicated that the most appropriate models were SARIMA(3,1,2)(3,1,0)12 for Aqua and SARIMA(2,1,1)(0,1,3)12 for Terra. The root mean square error values derived from predictions based on these model configurations were 0.030 for the Aqua dataset and 0.018 for the Terra dataset, indicating the accuracy of the models in forecasting the respective data. The predictions demonstrated strong agreement with the observed data, revealing a sustained increase in AOD values over time.
地球大气层是一个通过调节辐射平衡来显著影响天气模式和气候的系统。通过大气过滤的入射和反射辐射平衡中的干扰构成了驱动地球温度、大气环流和气候机制的相互作用。由于极地对大气环流模式的影响，极地在维持全球气候平衡方面发挥着至关重要的作用。在这种情况下，监测大气变量及其随时间的变化对于了解和预测全球气候变化至关重要。本研究研究了对大气变化高度敏感的南极地区气溶胶光学深度（AOD）的长期变化。该研究利用中分辨率成像光谱仪（MODIS） Aqua和Terra AOD产品在三个不同大小的区域进行研究。在空间基础上，分析了近20 a AOD的时间变化特征，以了解AOD的变化规律和趋势。此外，利用Marambio气溶胶机器人网络（AERONET）站的数据和卫星数据进行了比较。利用Terra和Aqua卫星的数据分别进行了评估，从2002年到2022年，两个数据集的AOD值都有类似的增加趋势。Aqua和AERONET、Terra和AERONET的4个月平均AOD的相关系数分别为0.6488和0.6190。利用季节自回归综合移动平均（SARIMA）模型对卫星数据进行预测。基于这些数据集的预测分析表明，最合适的模型为Aqua的SARIMA(3,1,2)(3,1,0)12和Terra的SARIMA(2,1,1)(0,1,3)12。基于这些模型配置的预测得出的均方根误差值在Aqua数据集为0.030，在Terra数据集为0.018，表明模型在预测各自数据时的准确性。预测结果与观测数据非常吻合，表明AOD值随时间持续增加。
{"title":"Long-term aerosol optical depth analysis and prediction over the Antarctic Peninsula","authors":"Esra Günaydın , Mahmut Oğuz Selbesoğlu , Mustafa Fahri Karabulut , Işıl Erdoğdu , Beyza Nur Kılıç , Bahadır Çelik , Özgün Oktar , Burcu Özsoy","doi":"10.1016/j.polar.2025.101212","DOIUrl":"10.1016/j.polar.2025.101212","url":null,"abstract":"<div><div><span><span><span>The Earth's atmosphere is a system that significantly influences weather patterns and climate by regulating the radiation balance. Disturbances in the balance of incoming and reflected radiation filtered through the atmosphere constitute an interaction driving the planet's temperature, </span>atmospheric circulation<span>, and climate mechanism. The polar regions play a crucial role in maintaining the global climate balance due to their influence on atmospheric circulation patterns. In this context, monitoring atmospheric variables and their changes over time is critical for understanding and predicting global climate change. This study investigated the long-term variations of aerosol optical depth (AOD) in </span></span>Antarctica<span>, a region highly sensitive to atmospheric changes. The research utilized Moderate Resolution Imaging Spectroradiometer<span> (MODIS) Aqua and Terra AOD products across three different-sized areas. The temporal variations of AOD over a twenty-year period were examined on a spatial basis to understand the patterns and trends of AOD. Furthermore, a comparison was conducted using data from the Marambio Aerosol Robotic Network<span> (AERONET) station and satellite-based data. The evaluations were carried out separately using data from the Terra and Aqua satellites, and similar increasing trends in AOD values were observed for both datasets from 2002 to 2022. The correlation between the four-month mean AOD of Aqua and AERONET, as well as Terra and AERONET, was calculated as 0.6488 and 0.6190, respectively. A Seasonal Autoregressive Integrated Moving Average (SARIMA) model was applied to satellite-based data to predict the dataset's behavior in the near future. The predictive analysis based on these datasets indicated that the most appropriate models were SARIMA(3,1,2)(3,1,0)</span></span></span></span><sub>12</sub> for Aqua and SARIMA(2,1,1)(0,1,3)<sub>12</sub><span> for Terra. The root mean square error values derived from predictions based on these model configurations were 0.030 for the Aqua dataset and 0.018 for the Terra dataset, indicating the accuracy of the models in forecasting the respective data. The predictions demonstrated strong agreement with the observed data, revealing a sustained increase in AOD values over time.</span></div></div>","PeriodicalId":20316,"journal":{"name":"Polar Science","volume":"46 ","pages":"Article 101212"},"PeriodicalIF":2.0,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145739053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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