Polar Research (E-Journal)
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Pseudolamarckina pseudorjasanensis Dain, 1967 (Foraminifera) as a Kimmeridgian marker species and its significance for biostratigraphy, palaeoecology and palaeobiogeography
No full textThis study presents a taxonomical review of the species Pseudolamarckina pseudorjasanensis Dain, 1967 collected at different sampling levels from the central and northern parts of European Russia and from Western Siberia. Morphological and biometrical analyses show that P. pseudorjasanensis is characterized by wide intraspecific variabilities and may encompass various previously described Kimmeridgian species of the genus Pseudolamarckina. The first appearance of P. pseudorjasanensis is recorded from the latest Early Kimmeridgian of sub-Mediterranean to Arctic regions. Furthermore, P. pseudorjasanensis appears to be the marker species of the foraminiferal JF41 Zone in Kimmeridgian sections of sub-boreal, boreal and Arctic regions. This JF41 Zone is particularly significant for interregional correlations. Finally, P. pseudorjasanensis was widespread across the Kimmeridgian basins of the Northern Hemisphere and was associated with environments predominantly located in the middle sublittoral zone
A multi-year study of narwhal occurrence in the western Fram Strait—detected via passive acoustic monitoring
No full textPassive acoustic monitoring (PAM) has proven to be an efficient method for studying vocally active marine mammals in areas that are difficult to access on a year-round basis. In this study, a PAM recorder was deployed on an oceanographic mooring in western Fram Strait (78°50'N, 5°W) to record the acoustic presence of narwhals (Monodon monoceros) over a 3-yr period. Acoustic data were recorded for 14–17 min at the start of each hour from 25 September 2010 to 26 August 2011, from 2 September 2012 to 11 April 2013 and from 8 September 2013 to 27 April 2014. Pulsed and tonal signals, as well as echolocation clicks, were detected throughout the recording periods, demonstrating that this species is present in this region throughout the year. Generalized linear mixed-effect models showed a negative correlation between the acoustic presence of narwhals and very dense sea-ice cover (≥90%). Surprisingly, a positive correlation was found between the acoustic presence of narwhals and the presence of warm Atlantic Water in the area. Available data suggest that there might be a unique stock of narwhals in the Eurasian sector of the Atlantic Arctic that do not exhibit the “traditional” narwhal pattern of seasonal migration between coastal summering areas and offshore wintering grounds, but rather remain resident year-round in deep, offshore waters
Arctic fox dispersal from Svalbard to Canada: one female’s long run across sea ice
No full textWe report the first satellite tracking of natal dispersal by an Arctic fox (Vulpes lagopus) between continents and High-Arctic ecosystems. A young female left Spitsbergen (Svalbard Archipelago, Norway) on 26 March 2018 and reached Ellesmere Island, Nunavut, Canada, 76 days later, after travelling a cumulative distance of 3506 km, bringing her ca. 1789 km away (straight-line distance) from her natal area. The total cumulative distance travelled during the entire tracking period, starting when she left her natal area on 1 March 2018 and ending when she settled on Ellesmere Island on 1 July 2018, was 4415 km. This is among the longest dispersal events ever recorded for an Arctic fox. Crossing extensive stretches of sea ice and glaciers, the female moved at an average rate of 46.3 km/day ± 41.1 SD. The maximum movement rate was 155 km/day and occurred on the ice sheet in northern Greenland. This is the fastest movement rate recorded for this species. The northernmost location recorded was on the sea ice off northern Greenland at a latitude of 84.7°N. The Arctic fox was of the blue colour morph typical for coastal environments, where Arctic foxes are adapted to food webs without lemmings but with substantial inputs of marine food resources. The Arctic fox settled on Ellesmere Island in a food web with lemmings, thereby switching ecosystems. Our observation supports evidence of gene flow across Arctic regions, including those seasonally bridged by sea ice, found in studies of the circumpolar genetic structure of Arctic fox populations.
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This article has a related Erratum
Review of The life of José María Sobral: scientist, diarist, and pioneer in Antarctica, by Mary R. Tahan (2018). Cham, Switzerland: Springer International Publishing. 336 pp. ISBN 978-3-319-67267-0.
No full textThe life cycle of small- to medium-sized icebergs in the Amundsen Sea Embayment
No full textAn object-based method for automatic iceberg detection has been applied to Advanced Synthetic Aperture Radar images in the Amundsen Sea Embayment (ASE), Antarctica. The images were acquired between 1 January 2006 and 8 April 2012 under varying meteorological, oceanographic and sea-ice conditions. During this time period, the icebergs were counted (average 1370 ± 50) and their surface area was estimated (average 1537.5 km2). The average surface area was about 2.5 times larger than the annual calved area (620 km2), indicating that the average iceberg age in the ASE is about 2.5 years, which was confirmed by observed residence times based on drift tracks. Most of the ASE icebergs were less than 1500 m long, and almost 90% of them were smaller than 2 km2. The proportion of small- and medium-sized icebergs (84.4%) was significantly higher than in the open ocean, where large icebergs (>10 km2) account for nearly the whole iceberg surface area. The opposite was true for the freshly calved icebergs in the ASE. The data indicate that the creation of icebergs in the ASE is dominated by steady small- to medium-scale calving from ice shelves fringing the embayment. In addition, rare calving events of giant icebergs occur on a decadal timescale. There is also some import of icebergs from the Bellingshausen Sea further east along the coast, in particular after large calving events there
Surface heat budget in the Southern Ocean from 42°S to the Antarctic marginal ice zone: four atmospheric reanalyses versus icebreaker Aurora Australis measurements
No full textSurface heat fluxes from four atmospheric reanalyses in the Southern Ocean are evaluated using air–sea measurements obtained from the Aurora Australis during off-winter seasons in 2010–12. The icebreaker tracked between Hobart, Tasmania (ca. 42°S), and the Antarctic continent, providing in situ benchmarks for the surface energy budget change in the Subantarctic Southern Ocean (58–42°S) and the eastern Antarctic marginal ice zone (MIZ, 68–58°S). We find that the reanalyses show a high-level agreement among themselves, but this agreement reflects a universal bias, not a “truth.” Downward shortwave radiation (SW↓) is overestimated (warm biased) and downward longwave radiation (LW↓) is underestimated (cold biased), an indication that the cloud amount in all models is too low. The ocean surface in both regimes shows a heat gain from the atmosphere when averaged over the seven months (October–April). However, the ocean heat gain in reanalyses is overestimated by 10–36 W m−2 (80–220%) in the MIZ but underestimated by 6–20 W m−2 (7–25%) in the Subantarctic. The biases in SW↓ and LW↓ cancel out each other in the MIZ, causing the surface heat budget to be dictated by the underestimation bias in sensible heat loss. These reanalyses biases affect the surface energy budget in the Southern Ocean by meaningfully affecting the timing of the seasonal transition from net heat gain to net heat loss at the surface and the relative strength of SW↓ at different regimes in summer, when the length-of-day effect can lead to increased SW↓ at high latitudes
Incomplete degradation of lichen usnic acid and atranorin in Svalbard reindeer (Rangifer tarandus platyrhynchus)
No full textPrevious studies of Eurasian tundra reindeer (Rangifer tarandus tarandus) in Norway indicate that their rumen microbiota play a key role in degrading lichen secondary metabolites. We investigated the presence of usnic acid and atranorin in faecal samples from Svalbard reindeer (R. tarandus platyrhynchus). Samples were collected in Bolterdalen valley together with vegetation samples from the study site. The mesic tundra in this area was dominated by vascular plants (59% of vegetation cover). Bryophytes (16%) and lichens (25%) were also present. Qualitative and quantitative analyses of usnic acid and atranorin in lichen and faeces samples were performed using high-performance liquid chromatography. Contents of atranorin averaged 12.49 ± 0.41 mg g–1in the thalli of Stereocaulon alpinum, while the average level of usnic acid was lowest in Cladonia mitis (12.75 ± 2.86 mg g–1) and highest in Flavocetraria cucullata (34.87 ± 0.47 mg g–1). Atranorin and usnic acid were detected in the faecal samples, averaging 0.41 ± 0.53 and 0.74 ± 1.11 (mean ± SD) mg g–1 dry matter, respectively. The presence of lichen secondary compounds in faeces from Svalbard reindeer shows that lichens are indeed included in their diet, although probably in small amounts because of depleted pastures. Contrary to previous findings in reindeer on mainland Norway, atranorin and usnic acid are not completely degraded or absorbed in Svalbard reindeer. To elucidate the mechanisms behind detoxification of lichen secondary compounds in reindeer, more research is needed on their respective rumen microbiomes and digestive enzymes
Comparison of passive microwave remote-sensing snow-depth products on Arctic sea ice
No full textChanges in snow cover on the surface of Arctic sea ice affect the energy balance between the atmosphere and the ocean and play a vital role in the global climate system. Accurate snow depth is a precondition for representing thermodynamic processes in sea-ice systems and is helpful for estimating sea-ice thickness. To better apply Arctic snow-depth products released by different organizations, we compared four kinds of snow-depth products based on three kinds of passive microwave (PM) sensors and evaluated them against the snow depth measured by ice mass-balance buoys (IMB snow depth) and Operation Ice Bridge airborne snow radar (OIB snow depth). The results show that the snow depths from the product released by the University of Bremen (UB) are larger than those by the National Snow and Ice Data Center (NSIDC) and National Aeronautics and Space Administration (NASA), with an average difference of 10 cm. Comparing the PM remote-sensing snow depths released by UB, NSIDC and NASA against IMB and OIB snow depths, it is found that NSIDC AMSR-E snow-depth product has the highest accuracy. Although these PM remote-sensing snow-depth products released by different organizations differ in accuracy, they all reflect the spatio-temporal variation characteristics of snow depth on Arctic sea ice. These comparisons and analysis of snow-depth products from different sensors released by different organizations provide a basis for further investigation of Arctic sea-ice thickness estimation and benefit the studies of Arctic sea ice and climate change
No second-in-command: human fatigue and the crash of the airship Italia revisited
No full textThe dirigible Italia crashed onto the Arctic sea ice north-east of the Svalbard archipelago on 25 May 1928 at 10:33 GMT while travelling back to her base from the North Pole. Only eight of the 16 crew members survived: one was killed upon impact, one did not survive the post-crash ordeal and six were trapped in the airship envelope (i.e., the balloon), which floated away and disappeared. No definite conclusions have ever been reached about the causes of the crash. The judgements of the Commission of Inquiry instituted by the Italian government and published in 1929 are carefully examined. Recent analysis has presented evidence that the mishap may have been fatigue-related. In this paper, the pivotal question of why General Nobile was so sleep-deprived at the time of the accident is addressed, specifically with reference to the lack of a second-in-command (i.e., a deputy commander) during the flight. Such a position was a standard practice for airships at the time, and General Nobile himself described this position as one necessary for an airship. Nevertheless, for a variety of reasons he proceeded on the Italia expedition without an official crew member responsible for this role. The lack of a second-in-command is proposed as a possible major contributing factor in the overall sequence of events leading to the crash of the Italia, although other possible causes and contributing factors for the crash are also considered, including structural failures, crew selection and political obstacles
Distribution and fluxes of dissolved organic carbon in the Arctic Ocean
No full textDissolved organic carbon, from marine biota excretions and decomposing detritus, is one of the main components of the carbon cycle in the ocean. In this study, an attempt was made to construct maps of the distribution and fluxes of DOC in the Arctic Ocean and the exchanges with the Pacific and Atlantic Oceans. Because of the limited data available a multiple linear regression technique was performed to identify significant relationships between DOC (2200 samples) and hydrologic parameters (temperature and salinity), as well as depth, horizon, latitude and offshore distance. Mapping of the DOC distribution and its fluxes was carried out at 38 horizons from 5 to 4150 m depth (resolution 1°×1°). Data on temperature, salinity and meridional and zonal components of current velocities were obtained from the Ocean Re-Analysis System 4 (ORAS4) database. All these parameters were averaged for the June–October period, the season of water sampling. The import of DOC in the Arctic Ocean is estimated to be 206 ± 17Tg C yr−1, and the export is 194 ± 23Tg C yr−1, so the import–export is balanced within the errors