Japanese Antarctic Research Expedition Research Articles

Observation of wave propagation over 1,000 km into Antarctica winter pack ice

ABSTRACT A drifting wave-ice buoy (Medusa-766) was deployed at the Lützow-Holm Bay (LHB) marginal ice zone in Antarctica during the 63rd Japanese Antarctic Research Expedition to study the wave influence on the unstable LHB fast ice. Medusa-766 survived the Antarctic winter as it was located deep in the ice cover with the shortest distance to the ice-free Southern Ocean over 1,000 km; at this time, there was evidence of 8-cm-height wave signal at the buoy position. Using the the ECMWF’s reanalysis wave data, we show that the incoming waves were likely 4-m waves that were generated by an extratropical cyclone in the Southern Ocean. Wave-induced ice breakup potential for this event could extend hundreds of kilometres into the ice field. When Medusa-766 was in LHB in the summer months, it did not detect sizable wave energy despite the low sea ice concentration extent even during on-ice wave events. Understanding the wave attenuation characteristics is needed to elucidate the ocean wave effect to the unstable LHB fast ice. The success of Medusa-766 demonstrates the robustness of the general design and the high sensitivity of the sensor used, which is promising for future LHB wave–ice interaction research.

Challenges in Detecting Clouds in Polar Regions Using a Drone with Onboard Low-Cost Particle Counter

It is expected that uncrewed aerial vehicles (UAVs) will be used increasingly for operational atmospheric soundings to cover a broader area of the lower troposphere, including that in the polar regions and over the oceans. During the Japanese Antarctic Research Expedition of 2022/2023, 172 vertical profiles up to a maximum height of 1000 m a.s.l. were conducted from mid-December 2022 to mid-March 2023 using a commercially available inexpensive drone launched from the icebreaker RV Shirase. Over a quarter of the flights encountered clouds and snow, of which half produced icing on the body and blades of the drone. The onboard aerosol counter detected an increase in the particle number concentration in the cloud layers, which was synchronized with an increase in the attenuated backscatter coefficient of a shipboard lidar ceilometer. In the presence of icing, the concentration of particles >1.0μm exceeded 5000 particles L−1 as a median value, while the concentration was <1000 particles L−1 for cases without icing. Using an onboard aerosol counter and/or land-based ceilometer would be useful for detecting the icing environments.

Helicopter‐Based Ocean Observations Capture Broad Ocean Heat Intrusions Toward the Totten Ice Shelf

AbstractThe recent discovery of warm ocean water near the Totten Ice Shelf (TIS) has increased attention to the Sabrina Coast in East Antarctica. We report the result of 6‐day helicopter‐based observations conducted during the 61st Japanese Antarctic Research Expedition (JARE61), revealing warm ocean water (0.5–1°C) occupying a large previously unsampled area of the Sabrina Coast (116.5°E−120°E) below 550–600 m. Along the TIS front, we observe modified Circumpolar Deep Water (mCDW) well above freezing (∼−0.7°C), consistent with previous work. We identify glacial meltwater outflow from the TIS cavity west of 116°E. No signs of mCDW intrusions toward the Moscow University Ice Shelf cavity are observed; however, those observations were limited to only two shallow (∼330 m) profiles. We also highlight the advantages of helicopter‐based observations for accessibility, speed, maneuverability, and cost‐efficiency. The combination of ship‐ and helicopter‐based observations using the JARE61 approach will increase the potential of future polar oceanographic observations.

Sightings of Cetaceans during JARE - 56 in the Indian Sector of the Southern Ocean

The cetacean observation was made during the 56th Japanese Antarctic Research Expedition (JARE - 56) cruise on the icebreaker SHIRASE, from 30 November to 15 December 2014 and from 15 February to 9 March 2015, in the Indian Ocean Sector of the Southern Ocean. A total of 28 sightings with 64 individuals of four cetacean species, humpback whale, (Megaptera novaeangliae), fin whale (Balaenoptera physalus), Antarctic minke whale (Balaenoptera bonaerensis), and killer whale (Orcinus orca), are reported. The most sighted species was the humpback whale (13 sightings) and the maximum number of individuals in a group was six for the same species. All sightings were made higher than 60 degrees South, close to the Antarctica coast.

A New Species of Bisexual Milnesium (Eutardigrada: Apochela) Having Aberrant Claws from Innhovde, Dronning Maud Land, East Antarctica.

There have been several records in the last 60 years for East Antarctica for Milnesium tardigradum Doyère, 1840 sensu lato, now considered a species complex. During the 56th Japanese Antarctic Research Expedition summer operation (2014-2015), a new tardigrade species in the genus Milnesium Doyère, 1840 was found in an ice-free Innhovde area along Lützow-Holm Bay, Dronning Maud Land, East Antarctica. The new species has aberrant claws with four to seven points on each secondary claw branch, which distinguishes it from other Milnesium species. A male specimen was found in the population and evidence showed that an isolated adult female moulted twice without oviposition. This strongly suggested bisexual reproduction for this population. The new species, Milnesium rastrum sp. nov., is described with its phylogenetic position and a discussion on the reproductive strategies for the harsh environments.

Relationship between Urinary Metabolomic Profiles and Depressive Episode in Antarctica.

Antarctic expeditions have a high risk of participant depression owing to long stays and isolated environments. By quantifying the stress state and changes in biomolecules over time before the onset of depressive symptoms, predictive markers of depression can be explored. Here, we evaluated the psychological changes in 30 participants in the Japanese Antarctic Research Expedition using the Patient Health Questionnaire-9 (PHQ-9). Urinary samples were collected every three months for a year, and comprehensive urinary metabolomic profiles were quantified using liquid chromatography time-of-flight mass spectrometry. Five participants showed major depressive episodes (PHQ-9 ≥ 10) at 12 months. The urinary metabolites between these participants and the 25 unaffected participants were compared at individual metabolite and pathway levels. The individual comparisons showed the most significant differences at 12 months in 14 metabolites, including ornithine and beta-alanine. Data from shorter stays showed less significant differences. In contrast, pathway and enrichment analyses showed the most significant difference at three months and a less significant difference at longer stays. These time transitions of urinary metabolites could help in the development of urinary biomarkers to detect subjects with depressive episodes at an early stage.

Spatial variations of 10Be in surface snow along the inland traverse route of Japanese Antarctic Research Expeditions

To contribute further to understanding of the nature of 10Be deposition in Antarctica, we determined 10Be concentrations in surface snow samples obtained along the inland traverse route of the 59th and 60th Japanese Antarctic Research Expeditions (JAREs) in eastern Dronning Maud Land. The 10Be concentrations ranged between 3.7 × 103 and 8.6 × 104 atoms/g. When plotted against latitude, they showed a clear trend of increasing concentration southward with an upward inflection point at around 75°S (elevation 3.5 km) for the 59th JARE. Comparison with both snow accumulation rate and δ18O data suggests that the inflection point divides the dominant deposition regime into two different groups: wet deposition (north of 75°S) and dry deposition with slight enhancement of 10Be fallout further inland (south of 75°S). Additional factors associated with 10Be transport from the stratosphere are also proposed.

Relationship between Modern Deep-Sea Ostracods and Water Mass Structure in East Antarctica

This study investigated the relationship between the distribution of modern ostracod biofacies and environmental factors in Lützow–Holm Bay, off Cape Darnley, and off Totten Glacier in East Antarctica. We collected study samples from water depths of 219 to 987 m by the 61st Japanese Antarctic Research Expedition. Nineteen species belonging to 13 genera and 47 species belonging to 31 genera of ostracods were found in three samples from Lützow–Holm Bay and ten samples from off Totten Glacier, respectively. We found no ostracods in the samples off Cape Darnley. Q-mode cluster analysis reveals four ostracod biofacies (A to D). Antarctiloxoconcha frigida (Neale, 1967) and Australicythere polylyca (Müller, 1908) were common under the influence of cold water in the upper bathyal zone (biofacies A to C). The genus Krithe was the most abundant taxon in biofacies D with low dissolved oxygen and high-water temperature (0.38°C, 34.66, and 5.0 ml/L, respectively), indicating the presence of warm deep seawater, i.e., modified Circumpolar Deep Water. Thus, we have checked the relationships between the ostracod assemblages and the environmental parameters analyzed in Lützow–Holm Bay and off Totten Glacier, and so strengthened the previous ostracod and environmental data.

Ostracoda and Paleoenvironment of Holocene-Raised Beach Sediment in Skarvsnes, East Antarctica

Four sediment samples were collected from an outcrop of the Holocene-raised beach in Skarvsnes (Lützow-Holm Bay, East Antarctica) at an elevation of 0–10 m through a geomorphological survey conducted during the 46th Japanese Antarctic Research Expedition (JARE 46). These samples were used for grain size, CNS (carbon, nitrogen, and sulfur) elemental, and ostracod analyses. The 14C dating of an annelid tube collected from the same outcrop was also conducted using an accelerator mass spectrometry. The resultant age was estimated at approximately 5,800 cal. year BP. A total of 16 ostracod species belonging to 10 genera were identified for the first time from all study samples near Lake Suribachi-Ike, Lützow–Holm Bay, East Antarctica. The phytal species were found to be the most dominant, suggesting rich seagrass and/or seaweeds at that time. Autecological methods and modern analog technique of ostracod assemblages were used to estimate the paleoenvironment. The result from the modern analog technique suggested that the paleo-water depth of approximately 30 m at that time is the most probable estimation, implying the glacial-isostatic uplift of approximately 30–40 m (5.1–6.8 mm/year) until sample date.

High-resolution subglacial topography around Dome Fuji, Antarctica, based on ground-based radar surveys over 30 years

Abstract. The retrieval of continuous ice core records of more than 1 Myr is an important challenge in palaeo-climatology. For identifying suitable sites for drilling such ice, knowledge of the subglacial topography and englacial layering is crucial. For this purpose, extensive ground-based ice radar surveys were carried out over Dome Fuji in the East Antarctic plateau during the 2017/18 and 2018/19 austral summers by the Japanese Antarctic Research Expedition, on the basis of ground-based radar surveys conducted over the previous ∼ 30 years. High-gain Yagi antennae were used to improve the antenna beam directivity, thereby significantly decreasing hyperbolic features of unfocused along-track diffraction hyperbolae in the echoes from mountainous ice–bedrock interfaces. We combined the new ice thickness data with the previous ground-based data, recorded since the 1980s, to generate an accurate high-spatial-resolution (up to 0.5 km between survey lines) ice thickness map. This map revealed a complex landscape composed of networks of subglacial valleys and highlands. Based on the new map, we examined the roughness of the ice–bed interface, the bed surface slope, the driving stress of ice and the subglacial hydrological condition. These new products and analyses set substantial constraints on identifying possible locations for new drilling. In addition, our map was compared with a few bed maps compiled by earlier independent efforts based on airborne radar data to examine the difference in features between datasets. Our analysis suggests that widely available bed topography products should be validated with in situ observations where possible.

Meteorological observations at Syowa Station in 2018 by the 59th Japanese Antarctic Research Expedition

Meteorological observations at Syowa Station in 2018 by the 59th Japanese Antarctic Research Expedition

GNSS Observations of GIA‐Induced Crustal Deformation in Lützow‐Holm Bay, East Antarctica

AbstractThe Japanese Antarctic Research Expeditions have conducted long‐term Global Navigation Satellite System (GNSS) observations at a series of bedrock outcrops along the coast of Lützow‐Holm Bay, East Antarctica, to elucidate the solid Earth response to ice mass changes. These GNSS observations capture both the viscoelastic response of the solid Earth to Antarctic Ice Sheet changes since the Last Glacial Maximum, termed glacial isostatic adjustment (GIA), and elastic deformation associated with recent surface mass changes due to snowfall variations. Here, we extract the GIA signals from the Lützow‐Holm Bay GNSS data by applying an elastic deformation correction based on the mass fluctuations observed in the Gravity Recovery and Climate Experiment and the satellite altimetry. Our results indicate that the region is currently experiencing approximately 1 mm/yr of subsidence, which is large enough to influence GIA model estimations. The resultant GIA‐induced deformation response in Lützow‐Holm Bay is 1–6 mm/yr of uplift.

Generation and Utility of a Digital Surface Model Based on Archived Aerial Photographs Taken by the Japanese Antarctic Research Expedition

Generation and Utility of a Digital Surface Model Based on Archived Aerial Photographs Taken by the Japanese Antarctic Research Expedition

Deep ice core drilling to a depth of 3035.22 m at Dome Fuji, Antarctica in 2001–07

AbstractThe Japanese second deep ice coring project was carried out at Dome Fuji, Antarctica. Following the drilling of the pilot hole in 2001, deep ice core drilling led by the Japanese Antarctic Research Expedition (JARE) was conducted over four austral summer seasons, beginning with the 2003/04 season and reached a depth of 3035.22 m near the bedrock in January 2007. The new drill was designed and developed with the goals of (1) solving the problems encountered during the first JARE deep coring drill and (2) achieving more efficient drilling. In particular, the maximum core length that can be drilled at one time was increased from 2.30 m to 3.84 m and the chip storage efficiency was enhanced by a special pipe with many small holes. This paper gives an outline of the improved drilling system, the progress of drilling and various drilling data.

Spatiotemporal variation of ice sheet melting in the Antarctic coastal marginal zone and the influence of ice lenses and rain using satellite microwave observation

This study uses satellite microwave observations to examine the spatiotemporal variations of melting ice sheets on the slopes of Antarctica. These observations were focused on the coastal marginal zone and inland traverse route near Syowa Station. Melting was detected using a 36 GHz vertical polarization diurnal amplitude variation (DAV). Data from the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) and AMSR2 during 2002–2011 and 2012–2017, respectively, showed DAV variations over time. It was estimated that the greatest melting extent occurred during the 2003/2004 summer; the DAV rose even in the inland areas. In contrast, DAV decreased during rain periods, which was reported by the Japanese Antarctic Research Expedition in 2004 and 2012. This is due to the rise in nighttime brightness temperature (TB). whereas the signal from rain was limited to the lower area. Coastal zones showed a low TB. The low coastal emissions may be attributed to the refrozen ice lenses under the coastal snow layers. The DAV can be significant as the contrast between daytime and nighttime increases from this low TB zone.

Soil Yeasts in the Vicinity of Syowa Station, East Antarctica: Their Diversity and Extracellular Enzymes, Cold Adaptation Strategies, and Secondary Metabolites

Antarctica is known as one of the harshest environments on Earth, with a frigid and dry climate. Soil yeasts living in such extreme environments can grow by decomposing organic compounds at sub-zero temperatures. Thus far, a list of lichen and non-lichen fungi isolated from the area near Syowa Station, the base of the Japanese Antarctic research expedition, has been compiled and a total of 76 species of fungi have been reported. Yeast, especially basidiomycete yeast, is the dominant fungus in Antarctica. This mini-review summarizes a survey of the yeast diversity in the soil of Eastern Ongul Island and the ability of these yeasts to secrete extracellular enzymes. We also describe the yeast diversity in the soil of the Skarvesnes ice-free region and how these yeasts have adapted to the sub-zero environment. Further, we describe the secondary metabolites of these yeasts, whose production is induced by cold stress.

Evaluating Health Impact at High Altitude in Antarctica and Effectiveness of Monitoring Oxygen Saturation.

The Japanese Antarctic Research Expedition (JARE) has been conducting research activities in inland Antarctica, which is extremely cold dryland covered with a thick ice sheet. This environment may cause a health disorder called acute mountain sickness (AMS). To improve the safety of expedition members, we evaluated the impact of extreme environmental conditions on human health and the effectiveness of monitoring of hypoxia for the early detection of AMS. In total, 9 members from JARE 59 were studied. Dome Fuji Station (Dome F), located 3,810 m above sea level (ASL), was the destination of the research party. We analyzed daily AMS scores (higher values correspond to more severe AMS-related symptoms), physiological findings, and percutaneous arterial blood oxygen saturation (SpO2) during the inland activity. We also determined the factors related to AMS scores. The average AMS score on arrival at Dome F was significantly higher than that at the departure point (560 m ASL). The average SpO2 level was significantly lower than that at other points. The SpO2 level correlated negatively with the AMS score in Spearman's rank correlation. Generalized estimating equations analysis showed that the AMS score was negatively associated with SpO2 level and positively associated with age. Hypoxia is a contributory factor to AMS which we can easily assess by measuring the SpO2 level with a pulse oximeter. SpO2 monitoring is a potentially useful health management tool for members in inland Antarctic expeditions. In addition, our results are helpful for understanding physiological responses and health issues in extreme environments.

Disease and injury statistics of Japanese Antarctic research expeditions during the wintering period: evaluation of 6837 cases in the 1st–56th parties – Antarctic health report in 1956–2016

ABSTRACT This study aimed to evaluate disease and injury trends among wintering members of the Japanese Antarctic Research Expedition. Obtained information is indispensable to the advancement of medical system and research. Summation was performed based on medical records of reports prepared by each expedition over the period 1956–2016. The clinical department’s classification methods of the names of injuries and diseases varied among expeditions, but the names were integrated following the same classification. Of 1734 members (29 women), 6837 disease or injury cases (4 cases/person) were recorded. The rates of cases were as follows: surgical-orthopaedic (45.3%), internal medical (21.7%), dental (11.6%), dermatological (8.4%), ophthalmological (5.8%), otorhinolaryngological (5.3%), psychiatric (1.6%), and urological (0.1%) cases. There was no major change in rates by type of medical case in each expedition. This analysis made it possible to prepare medical facilities, content of physical examinations to select members, training of physicians before departure, preventive hygiene at sites, and medical research themes.

Activities of the summer operation of the 58th Japanese Antarctic Research Expedition (JARE-58) in 2016–2017

Activities of the summer operation of the 58th Japanese Antarctic Research Expedition (JARE-58) in 2016–2017

A catalog of fungi recorded from the vicinity of Syowa Station

The Japanese Antarctic Research Expedition (JARE) was started in 1957. The expedition marked its 60th anniversary in January 2017. In total 76 fungal species (61 ascomycetous fungi, including 9 unidentified species, and 16 basidiomycetous fungi) have thus far been recorded from the area around Syowa Station. In this review, I present a catalog of the fungal species isolated from the vicinity of Syowa Station to mark the 60th anniversary of JARE.