Anomalous variations in the thermohaline structure of the Arctic Ocean (Aus dem Russ. übersetzt)

Introduction: In the last two decades, significant changes have occurred in the Arctic Ocean as well as in the entire Arctic region. The ice cover of Arctic seas, which was gradually (linearly) decreasing from the beginning of the 20th century to the end of it [1], began to shrink rapidly in the 1990s and in the 21st century [2]. Salinity variations in the upper layer changed sign in different regions [3]. The temperature of Atlantic waters in the Arctic basin started to increase. At the end of the 1990s, stabilization of Atlantic water transport to the Arctic Basin was observed [4], but starting from 2004, the temperature of Atlantic waters in the Eurasian sub-basin increased even more and reached values that had not been observed here previously [5]. In 2007, extreme summer processes in the Arctic that followed this increase and anomalous state of the ice cover and upper layer of the ocean that were formed by the beginning of autumn put forward a pressing problem to evaluate the variation in the thermohaline structure of the Arctic Ocean as a whole

A Steady Regime of Volume and Heat Transports in the Eastern Arctic Ocean in the Early 21st Century

Mooring observations in the eastern Eurasian Basin of the Arctic Ocean showed that mean 2013–2018 along-slope volume and heat (calculated relative to the freezing temperature) transports in the upper 800 m were 4.8 ± 0.1 Sv (1 Sv = 106 m3/s) and 34.8 ± 0.6 TW, respectively. Volume and heat transports within the Atlantic Water (AW) layer (∼150–800 m) in 2013–2018 lacked significant temporal shifts at annual and longer time scales: averaged over the two periods of mooring deployment in 2013–2015 and 2015–2018, volume transports were 3.1 ± 0.1 Sv, while AW heat transports were 31.3 ± 1.0 TW and 34.8 ± 0.8 TW. Moreover, the reconstructed AW volume transports over longer, 2003–2018, period of time showed strong interannual variations but lacked a statistically significant trend. However, we found a weak positive trend of 0.08 ± 0.07 Sv/year in the barotropic AW volume transport estimated using dynamic ocean topography (DOT) measurements in 2003–2014 – the longest period spanned by the DOT dataset. Vertical coherence of 2013–2018 transports in the halocline (70–140 m) and AW (∼150–800 m) layers was high, suggesting the essential role of the barotropic forcing in constraining along-slope transports. Quantitative estimates of transports and their variability discussed in this study help identify the role of atlantification in critical changes of the eastern Arctic Ocean.publishedVersio

Secular sea level change in the Russian sector of the Arctic Ocean

Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 109 (2004): C03042, doi:10.1029/2003JC002007.Sea level is a natural integral indicator of climate variability. It reflects changes in practically all dynamic and thermodynamic processes of terrestrial, oceanic, atmospheric, and cryospheric origin. The use of estimates of sea level rise as an indicator of climate change therefore incurs the difficulty that the inferred sea level change is the net result of many individual effects of environmental forcing. Since some of these effects may offset others, the cause of the sea level response to climate change remains somewhat uncertain. This paper is focused on an attempt to provide first-order answers to two questions, namely, what is the rate of sea level change in the Arctic Ocean, and furthermore, what is the role of each of the individual contributing factors to observed Arctic Ocean sea level change? In seeking answers to these questions we have discovered that during the period 1954–1989 the observed sea level over the Russian sector of the Arctic Ocean is rising at a rate of approximately 0.123 cm yr−1 and that after correction for the process of glacial isostatic adjustment this rate is approximately 0.185 cm yr−1. There are two major causes of this rise. The first is associated with the steric effect of ocean expansion. This effect is responsible for a contribution of approximately 0.064 cm yr−1 to the total rate of rise (35%). The second most important factor is related to the ongoing decrease of sea level atmospheric pressure over the Arctic Ocean, which contributes 0.056 cm yr−1, or approximately 30% of the net positive sea level trend. A third contribution to the sea level increase involves wind action and the increase of cyclonic winds over the Arctic Ocean, which leads to sea level rise at a rate of 0.018 cm yr−1 or approximately 10% of the total. The combined effect of the sea level rise due to an increase of river runoff and the sea level fall due to a negative trend in precipitation minus evaporation over the ocean is close to 0. For the Russian sector of the Arctic Ocean it therefore appears that approximately 25% of the trend of 0.185 cm yr−1, a contribution of 0.048 cm yr−1, may be due to the effect of increasing Arctic Ocean mass.This material is based upon work supported by the National Science Foundation under grant 0136432

Тенденции многолетней изменчивости уровня моря на прибрежных станциях Северного Ледовитого океана

New estimates of linear trends in the position of the level surface were obtained as a result of analysis of the data of long-term observations of sea level fluctuations at the stations of the seas of the Arctic Ocean. A rise in sea level is observed at almost all stations. In multi-year fluctuations of the level, periods characterized by different values of linear trends are identified. The reasons for the variability of local linear trends in the level of the Arctic seas from the 1950-1980 stage to the 1990-2015 period are analyzed. It is shown that the presence of local trends during the annual average levels at coast stations is a consequence of changes in climatic conditions reflected in changes in atmospheric and hydrosphere climatic indices, as well as in freshwater river runoff.В результате анализа данных многолетних наблюдений за колебаниями уровня моря на станциях морей Северного Ледовитого океана получены новые оценки линейных трендов изменений положения уровенной поверхности. Практически на всех станциях, за исключением станции Баренцбург, наблюдается повышение уровня моря. В многолетнем ходе колебаний уровня выделены периоды, характеризующиеся различными значениями линейных трендов. Проанализированы причины изменчивости локальных линейных трендов уровня арктических морей от стадии 1950–1980 к стадии 1990–2015 гг. Показано, что наличие локальных трендов в ходе среднегодовых уровней на береговых станциях является следствием изменения климатических условий, отражающихся в изменениях атмосферных и гидросферных климатических индексов, а также пресноводном стоке рек

Ekstremaľnye izmeneniya temperatury i solenosti vody arkticheskogo poverkhnostnogo sloya v 2007-2009 gg. (The extreme changes of temperature and salinity in the Arctic Ocean surface layer in 2007-2009, in Russian)

This paper examines the temperature and salinity patterns and evolution in the surface layer of the Arctic Ocean in 2007-2009 and deals with the factors impacting the extreme changes both in temperature and salinity in 2007. The large areas of positive and negative anomalies in temperature and salinity have been formed over the Arctic Ocean with the apparant frontal barrier areea between Eurasian and American basins. The followed years (2008-2009) exhibit the reducing of thermohaline anomalies between the two basins assuming gradually rcovering to the initial state. Considering the mean salinities within 5-50 m depth one can claim that the positive linear trend is evident both in Eurasian and American basinss since 1950 to 1993 while the intensive freshening was obsserved in American basin in 2007-2009. We intend that these changes in salinity can be assumed as the signature of non-stationary nature of all Arctic marine environments

Heat, salt, and volume transports in the eastern Eurasian Basin of the Arctic Ocean from 2 years of mooring observations

This study discusses along-slope volume, heat, and salt transports derived from observations collected in 2013–2015 using a cross-slope array of six moorings ranging from 250 to 3900&thinsp;m in the eastern Eurasian Basin (EB) of the Arctic Ocean. These observations demonstrate that in the upper 780&thinsp;m layer, the along-slope boundary current advected, on average, 5.1±0.1&thinsp;Sv of water, predominantly in the eastward (shallow-to-right) direction. Monthly net volume transports across the Laptev Sea slope vary widely, from  ∼ 0.3±0.8 in April 2014 to  ∼ 9.9±0.8&thinsp;Sv in June 2014; 3.1±0.1&thinsp;Sv (or 60&thinsp;%) of the net transport was associated with warm and salty intermediate-depth Atlantic Water (AW). Calculated heat transport for 2013–2015 (relative to −1.8&thinsp;°C) was 46.0±1.7&thinsp;TW, and net salt transport (relative to zero salinity) was 172±6&thinsp;Mkg&thinsp;s−1. Estimates for AW heat and salt transports were 32.7±1.3&thinsp;TW (71&thinsp;% of net heat transport) and 112±4&thinsp;Mkg&thinsp;s−1 (65&thinsp;% of net salt transport). The variability of currents explains  ∼ 90&thinsp;% of the variability in the heat and salt transports. The remaining  ∼ 10&thinsp;% is controlled by temperature and salinity anomalies together with the temporal variability of the AW layer thickness. The annual mean volume transports decreased by 25&thinsp;% from 5.8±0.2&thinsp;Sv in 2013–2014 to 4.4±0.2&thinsp;Sv in 2014–2015, suggesting that changes in the transports at interannual and longer timescales in the eastern EB may be significant.</p

Sostoyanie sloya atlanticheskikh vod v Severnom Ledovitom okeane v 2007-2009 gg. (The state of Atlantic water layer in the Arctic Ocean in 2007-2009, in Russian)

Oceanographic studies during IPY 2007/2009 provided new information on spatial variability of hydrographic parameters. Detailed pattern of irregularities in the Atlantic Water (AW) layer was documented in the Nansen Basin. Spatial scales of temperature distribution and the depth of the upper boundary of AW were estimated. In the Canadian Basin spatial variations of temperature were less pronounced. During IPY 2007/2008 the area occupied by AW has increased. According to our estimations the positive temperature anomaly in some regions was as high as 1,5°C, which is about 70% of temperature maximum in 1950-1959. The upper boundary of AW (zero degree isotherm) rose by 40-120 m around the Mendeleyev Ridge and in the Amundsen Basin. At the same time, in the Canada Basin and in the western Fram Strait the AW thickness decreased by similar value. Heat content of the AW layer around the major part of the Arctic Ocean exceeded mean climatic value, except for the compact area north of Franz Josef Land, where small negative anomaly was observed. Throughout 2008 mean temperature and maximum temperature in the AW layer were higher than mean climatic values. At the same time, the state of AW layer in the inflow region, east of Fram Strait along the continental margin to the Laptev Sea, substantially changed in comparison with 2007. Mean and maximum temperature of AW dropped by 0,25/0,5°C. Heat content and the Thickness of AW layer have also decreased. Basing on the obtained results, we conclude that during 2008/2009 there was a neneral reverse trend in AW parameters towards mean climatic results

Spinning Strings as Small Black Rings

Certain supersymmetric elementary string states with spin can be viewed as small black rings whose horizon has the topology of S^1 \times S^{d-3} in a d-dimensional string theory. By analyzing the singular black ring solution in the supergravity approximation, and using various symmetries of the \alpha' corrected effective action we argue that the Bekenstein-Hawking-Wald entropy of the black string solution in the full string theory agrees with the statistical entropy of the same system up to an overall normalization constant. While the normalization constant cannot be determined by the symmetry principles alone, it can be related to a similar normalization constant that appears in the expression for small black holes without angular momentum in one less dimension. Thus agreement between statistical and macroscopic entropy of (d-1)-dimensional non-rotating elementary string states would imply a similar agreement for a d-dimensional elementary string state with spin. Our analysis also determines the structure of the near horizon geometry and provides us with a geometric derivation of the Regge bound. These studies give further evidence that a ring-like horizon is formed when large angular momentum is added to a small black hole.Comment: LaTeX file, 31 pages; v2: references to earlier work adde

Sea level variability in the Arctic Ocean from AOMIP models

Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 112 (2007): C04S08, doi:10.1029/2006JC003916.Monthly sea levels from five Arctic Ocean Model Intercomparison Project (AOMIP) models are analyzed and validated against observations in the Arctic Ocean. The AOMIP models are able to simulate variability of sea level reasonably well, but several improvements are needed to reduce model errors. It is suggested that the models will improve if their domains have a minimum depth less than 10 m. It is also recommended to take into account forcing associated with atmospheric loading, fast ice, and volume water fluxes representing Bering Strait inflow and river runoff. Several aspects of sea level variability in the Arctic Ocean are investigated based on updated observed sea level time series. The observed rate of sea level rise corrected for the glacial isostatic adjustment at 9 stations in the Kara, Laptev, and East Siberian seas for 1954–2006 is estimated as 0.250 cm/yr. There is a well pronounced decadal variability in the observed sea level time series. The 5-year running mean sea level signal correlates well with the annual Arctic Oscillation (AO) index and the sea level atmospheric pressure (SLP) at coastal stations and the North Pole. For 1954–2000 all model results reflect this correlation very well, indicating that the long-term model forcing and model reaction to the forcing are correct. Consistent with the influences of AO-driven processes, the sea level in the Arctic Ocean dropped significantly after 1990 and increased after the circulation regime changed from cyclonic to anticyclonic in 1997. In contrast, from 2000 to 2006 the sea level rose despite the stabilization of the AO index at its lowest values after 2000.This research is supported by the National Science Foundation Office of Polar Programs (under cooperative agreements OPP- 0002239 and OPP- 0327664) with the International Arctic Research Center, University of Alaska Fairbanks, and by the Climate Change Prediction Program of the Department of Energy’s Office of Biological and Environmental Research. The development of the UW model is also supported by NASA grants NNG04GB03G and NNG04GH52G and NSF grants OPP-0240916 and OPP-0229429

Состояние и перспективы развития системы мониторинга гидрологических условий акватории Северного Ледовитого океана

The article briefly substantiates the need for regular monitoring of the state of the waters of the Russian Arctic Seas and the Arctic Basin of the Arctic Ocean. The goals and objectives of monitoring hydrological conditions are formulated. General ideas about the development and construction of a system for monitoring hydrological conditions in the Arctic are expressed, taking into account the use of modern instruments and methods of oceanographic observations. It is shown that the most promising is the use of autonomous measuring complexes in the monitoring system, including moorings and drifting profiler buoys. The special value of satellite oceanographic data is emphasized. No less important are coastal observations carried out over the network of Roshydromet stations, as well as at research centers united into the Arctic Space-Distributed Observatory. The inclusion into this Observatory of the ice self-propelled platform “North Pole”, which will replace the drifting stations, will allow not only observing and measuring the main characteristics of the water masses, but also conducting controlled field experiments that will provide a deeper understanding of different-scale physical processes occurring in the waters of the Arctic Ocean. An important element of the monitoring system is data assimilation based on the use of numerical models that allow for the effect of the ice cover in the atmosphere-sea ice-ocean interaction system.В статье сформулированы цели и задачи мониторинга гидрологических условий, излагаются общие соображения о развитии и построении системы мониторинга гидрологических условий в Арктике с учетом использования современных средств и методов океанографических наблюдений и исследований. Показано, что наиболее перспективным представляется использование в системе мониторинга автоматических измерительных комплексов, включающих в себя заякоренные буйковые станции, дрейфующие буи-профилографы. Отмечена особая ценность данных спутниковой океанографии. Вместе с тем сохраняется ценность прибрежных наблюдений, выполняемых на сети станций Росгидромета, а также на базе научных центров, объединенных в Арктическую пространственно-распределенную обсерваторию. Включение в состав этой обсерватории ледостойкой самодвижущейся платформы «Северный полюс», идущей на смену дрейфующим станциям, даст возможность не только наблюдать и измерять основные характеристики водных масс, но и проводить управляемые натурные эксперименты, позволяющие глубже понять разномасштабные физические процессы, протекающие в водах Северного Ледовитого океана. Важным элементом системы мониторинга является усвоение данных, основанное на использовании численных моделей, учитывающих влияние ледяного покрова в системе взаимодействия атмосфера — морской лед — океан