On the circulation, water mass distribution, and nutrient concentrations of the western Chukchi Sea

Substantial amounts of nutrients and carbon enter the Arctic Ocean from the Pacific Ocean through the Bering Strait, distributed over three main pathways. Water with low salinities and nutrient concentrations takes an eastern route along the Alaskan coast, as Alaskan Coastal Water. A central pathway exhibits intermediate salinity and nutrient concentrations, while the most nutrient-rich water enters the Bering Strait on its western side. Towards the Arctic Ocean, the flow of these water masses is subject to strong topographic steering within the Chukchi Sea with volume transport modulated by the wind field. In this contribution, we use data from several sections crossing Herald Canyon collected in 2008 and 2014 together with numerical modelling to investigate the circulation and transport in the western part of the Chukchi Sea. We find that a substantial fraction of water from the Chukchi Sea enters the East Siberian Sea south of Wrangel Island and circulates in an anticyclonic direction around the island. This water then contributes to the high-nutrient waters of Herald Canyon. The bottom of the canyon has the highest nutrient concentrations, likely as a result of addition from the degradation of organic matter at the sediment surface in the East Siberian Sea. The flux of nutrients (nitrate, phosphate, and silicate) and dissolved inorganic carbon in Bering Summer Water and Winter Water is computed by combining hydrographic and nutrient observations with geostrophic transport referenced to lowered acoustic Doppler current profiler (LADCP) and surface drift data. Even if there are some general similarities between the years, there are differences in both the temperature–salinity and nutrient characteristics. To assess these differences, and also to get a wider temporal and spatial view, numerical modelling results are applied. According to model results, high-frequency variability dominates the flow in Herald Canyon. This leads us to conclude that this region needs to be monitored over a longer time frame to deduce the temporal variability and potential trends.

The opening and closure of oceanic seaways during the Cenozoic: pacemaker of global climate change?

The opening and constriction of oceanic gateways played an essential role in shaping global climate throughout Earth's history. In this review we provide an overview of the best documented feedbacks between gateway dynamics and climate change throughout the Cenozoic. The discussed tectonically induced events comprise (i) the opening of the Tasmanian Gateway and the glaciation of Antarctica during the Eocene/Oligocene, (ii) the water mass exchange between Atlantic and Mediterranean via the Strait of Gibraltar since the Miocene, (iii) the closure of the American Seaway, as well as (iv) the constriction of the Indonesian Throughflow, both argued to have been instrumental for intensification of the Northern Hemisphere Glaciation during the late Pliocene and early Pleistocene. Lastly, we look at (v) the climatic impact of the flooding and submergence of the Bering Strait during the Plio-Pleistocene and its influence on the Atlantic Meridional Overturning Circulation. While different in underlying mechanisms, geographic scale and temporal evolution, these case studies demonstrate that even seemingly small-scale changes in the configuration of ocean seaways fundamentally altered the global climate system via their impact on oceanic currents, global heat transfer, and carbon storage.

The climatic trends of temperature and salinity in the Bering straight in the last decades

Представлены результаты расчетов линейных климатических трендов температуры и солености поверхностных вод Берингова пролива и прилегающих акваторий за временной период 1950 – 2020 гг., отдельно за август и февраль месяцы. Отмечается нагрев поступающей тихоокеанской воды в Чукотское море в летний период на +0,120С/10лет, в зимний период +0,140С/10лет. Одновременно происходит временной тренд в сторону уменьшения солености поступающих вод, это ‒0,060/00/10лет в летний сезон и ‒0,03 S0/00/10лет в зимний сезон. Таким образом в случае инерционного изменения климата через 100 лет вода в Беринговом проливе будет на 1,30С теплее и на 0,450/00 менее соленой. Сделаны оценки роста потока тепла через Берингов пролив в Чукотское море вследствие климатического тренда, который составляет +2,4*1019Дж/10лет. Отмечено, что направления трендов температуры и солености в Беринговом море и Беринговом проливе в сторону нагрева и уменьшения солености совпадают, а в Чукотском море климатические тенденции противоположные. The calculation of the climatic linear trends of the surface waters temperature and salinity in the Bering Strait and nearby water areas are presented. The time period is 1950 – 2020 years. The Time data for the warm season - August and the cold season - February series are shown separately. The heating of the incoming Pacific water into the Chukchi Sea is note. There is the summer period +0.120C/decade, in the winter period +0.140C/decade. At the same time, there is some trend towards decrease in salinity the straight water, this is ‒0.06psu/decade in the summer season and this is ‒0.03psu/decade in the winter season. Following of an inertial climate change in 100 years there is the Bering Strait water will be +1.30Cwarmer and ‒0.45psu/decade salty less. The estimate of the heat flux increase through the Bering Strait to the Chukchi Sea due to the climatic trend is +2.4*1019J/decade. There is a peculiarity that the time trends of temperature and salinity in the Bering Sea and the Bering Strait have the same direction to the heating and the salinity decrease, but at the same time the Chukchi Sea has the opposite tendency. An explanation of this discrepancy is given.

Temporal variance of the ice navigation conditions within the Northern Sea Route

Recognition of satellite images, composition of them and vectorization is used in AARI for ice charts production. There is discussed methodology and results of the ice charts processing by means of computer programs, which were elaborated by Dr. Tretyakov in Python. The paper demonstrates results of analysis of temporal variance of ice navigation circumstances within the buffer zone of the marine transport system from the Sabetta Port (the Yamal Peninsula, Russia) up to the Bering Strait. There are considered the variance for April and May from 1998 up to 2020. This intra-annual interval is the one with the heaviest ice circumstances for shipping. We used conditional length of various age and age and form gradations of the sea ice for the route as a whole, as an integral parameter for estimation of the navigation hardships of ice navigation. The conditional length of an ice age (thickness) diapason is result of multiplication of the diapason partial concentration at the length of the route leg with homogeneous ice characteristics. There were produced series of the conditional lengths for each ten-day periods during April and May. Then statistical homogeneity of the series was tested by various methods.

Freshwater routing in eddy-permitting simulations of the last deglacial: the impact of realistic freshwater discharge

Freshwater, in the form of glacial runoff, is hypothesized to play a critical role in centennial- to millennial-scale climate variability, such as the Younger Dryas and Dansgaard–Oeschger events, but this relationship is not straightforward. Large-scale glacial runoff events, such as Meltwater Pulse 1a (MWP1a), are not always temporally proximal to subsequent large-scale cooling. Moreover, the typical design of hosing experiments that support this relationship tends to artificially amplify the climate response. This study explores the impact that limitations in the representation of runoff in conventional “hosing” simulations has on our understanding of this relationship by examining where coastally released freshwater is transported when it reaches the ocean. We particularly focus on the impact of (1) the injection of freshwater directly over sites of deep-water formation (DWF) rather than at runoff locations (i.e. hosing), (2) excessive freshwater injection volumes (often by a factor of 5), and (3) the use of present-day (rather than palaeo) ocean gateways. We track the routing of glaciologically constrained freshwater volumes from four different inferred injection locations in a suite of eddy-permitting glacial ocean simulations using the Massachusetts Institute of Technology General Circulation Model (MITgcm) under both open and closed Bering Strait conditions. Restricting freshwater forcing values to realistic ranges results in less spreading of freshwater across the North Atlantic and indicates that the freshwater anomalies over DWF sites depend strongly on the geographical location of meltwater input. In particular, freshwater released into the Gulf of Mexico generates a very weak freshwater signal over DWF regions as a result of entrainment by the turbulent Gulf Stream. In contrast, freshwater released into the Arctic with an open Bering Strait or from the Eurasian ice sheet is found to generate the largest salinity anomalies over DWF regions in the North Atlantic and GIN (Greenland–Iceland–Norwegian) seas region respectively. Experiments show that when the Bering Strait is open, the Mackenzie River source exhibits more than twice as much freshening of the North Atlantic deep-water formation regions as when the Bering Strait is closed. Our results illustrate that applying freshwater hosing directly into the North Atlantic with even “realistic” freshwater amounts still overestimates the amount of terrestrial runoff reaching DWF regions. Given the simulated salinity anomaly distributions and the lack of reconstructed impact on deep-water formation during the Bølling–Allerød, our results support that the majority of the North American contribution to MWP1a was not routed through the Mackenzie River.

Species-specific reservoir effect estimates: A case study of archaeological marine samples from the Bering Strait

Due to the marine reservoir effect, radiocarbon dates of marine samples require a correction. Marine reservoir effects, however, may vary among different marine species within a given body of water. Factors such as diet, feeding depth and migratory behaviour all affect the 14C date of a marine organism. Moreover, there is often significant variation within single marine species. Whilst the careful consideration of the Δ R values of a single marine species in a given location is important, so too is the full range of Δ R values within an ecosystem. This paper illustrates this point, using a sample pairing method to estimate the reservoir effects in 17 marine samples, of eight different species, from the archaeological site of Ekven (Eastern Chukotka, Siberia). An OxCal model is used to assess the strength of these estimates. The marine reservoir effects of samples passing the model range from Δ R (Marine20) = 136 ± 41–Δ R = 460 ± 40. Marine reservoir effect estimates of these samples and other published samples are used to explore variability in the wider Bering Strait region. The archaeological implications of this variability are also discussed. The calibrating of 14C dates from human bone collagen, for example, could be improved by applying a dietary relevant marine reservoir effect correction. For humans from the site of Ekven, a Δ R (Marine20) correction of 289 ± 124 years or reservoir age correction of 842 ± 123 years is suggested.

Missionary theology and the peopling of pre-Columbian America: John Oxenbridge’s “A plea for the dumb Indian” (ca. 1666)

John Oxenbridge was a 17th-century Puritan minister who lived in England, Bermuda, Suriname, Barbados, and New England. During his residence in Suriname, a short-lived English colony, he wrote a missionary treatise he entitled “A plea for the dumb Indian.” The work was never published and survives partially in non-digitalized manuscript form at the Massachusetts Historical Society in Boston. One of the intact portions of the manuscript is a discussion of the settlement of pre-Columbian America. Oxenbridge held that the Native Americans were descended from ancient Scythians, the semi-nomadic and “uncivilized” peoples of the vast Eurasian Steppe, who had entered America through “Anian,” an early modern designation for the region around the Bering Strait. He also thought that two other peoples later settled in pre-Columbian America: Welsh adventurers sailed across the Atlantic but soon intermarried with the Native Americans and disappeared as a distinct people, and some of the lost tribes of Israel entered the New World through Anian. These lost Israelites still survived and continued to observe the Mosaic Law. They never intermarried with the Native Americans; however, they passed on a “tincture of Israels customs” to their Indian neighbors. Oxenbridge’s discussion of the peopling of pre-Columbian America may seem like an antiquarian curiosity of little interest to historians of Christian missions. But for him it remained relevant to the present day. The Welsh migration, which he thought predated Spanish and French colonization, legitimated the English imperial claim in America. More importantly, the presence of lost Israelites in Scythian America would facilitate the conversion of the Native Americans.