Arctic Ocean variability derived from historical observations

This study has been motivated by reports of extraordinary change in the Arctic Ocean observed in recent decades. Most of these observations are based on synoptic measurements, while evaluation of anomalies requires an understanding of the underlying long-term variability. Historical climatologies give reference means, and while these datasets are a reliable source of the mean Atlantic Layer temperature, they significantly underestimate variability. Using historical data, we calculated statistical parameters for selected Arctic Ocean regions. They demonstrate a high level of Atlantic Layer temperature variability in the Nansen Basin and sea-surface salinity fluctuations on the Siberian shelf and the Amundsen Basin. These estimates suggest strong limitations on our ability to define amplitudes of anomalies by comparing recent synoptic measurements with climatologies, especially for regions characterized by strong variability

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

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

Межгодовая изменчивость характеристик поверхностного слоя и галоклина Арктического бассейна

As the area of the sea ice cover has considerably reduced in the recent years, the Arctic Ocean surface layer has become more exposed to the effect of atmospheric processes. In order to evaluate the influence of the new conditions on the surface layer state, a large array of winter oceanographic data was used to calculate the Arctic Ocean mixed layer thickness and salinity along with the thickness and salinity of the halocline layer for the 1950-2013 period. Analysis of the interannual variability of the surface layer parameters listed has shown that the mixed layer thickness has increased in recent years, from 30-35 m in 1950-70s to 40-44m in 1980-2000s. The halocline thickness, conversely, has decreased from 65m in 1950-90s to 50 in the 2000s. At the same time, mixed layer salinity and the salinity of the halocline layer has become lower in the 2000s by about 0,5 % compared with 1950-90s. Three periods with distinctive configurations of the fields of the surface layer parameters have been identified. These quasi-20-year periods correspond to different climatic stages with different regimes of the atmospheric circulation. However, this is certainly not the only cause of the changes that occur in the surface layer condition. To reveal other causes of these changes, statistical methods were used to analyze the time series of the Arctic Ocean surface layer parameters. Linear regression equations allowed us to find out that the variability of the mixed layer thickness and salinity is almost equally determined by changes of the atmospheric circulation and fluctuations of the water exchange with the neighboring oceans along with river runoff and ice processes. At the same time, the thickness and salinity of the halocline layer strongly correlate with mixed layer parameters and, as there is no direct contact with the atmosphere, their variability is determined mostly by the mixed layer condition and the underlying Atlantic waters.В связи с уменьшением площади ледяного покрова верхний слой Северного Ледовитого океана в последние годы стал более доступен для непосредственного влияния ветра и солнечной радиации. В данной статье особое внимание уделяется исследованию реакции верхнего слоя на изменения условий окружающей среды и вероятных механизмов проявления данных изменений в изменчивости состояния верхнего слоя. Был проанализирован массив океанологических данных за зимний период 1950-2013 гг., произведен расчет толщины и солености верхнего перемешанного слоя, а также толщины и солености слоя галоклина. На основе уравнений линейной регрессии были получены статистические модели связи перечисленных параметров верхнего слоя с различными факторами окружающей среды, такими как индексы атмосферной циркуляции, водообмен с соседними океанами, речной сток и ледовые процессы

Observational program tracks Arctic Ocean transition to a warmer state

Over the past several decades, the Arctic Ocean has undergone substantial change. Enhanced transport of warmer air from lower latitudes has led to increased Arctic surface air temperature. Concurrent reductions in Arctic ice extent and thickness have been documented. The first evidence of warming in the intermediate Atlantic Water (AW, water depth between 150 and 900 meters) of the Arctic Ocean was found in 1990. Another anomaly, found in 2004, suggests that the Arctic Ocean is in transition toward a new, warmer state [Polyakov et al., 2005, and references therein]

Информативность гидрометеорологических и астрогеофизических факторов в задаче описания межгодовых колебаний ледовитости Гренландского моря

The interannual changes in ice coverage in the Greenland Sea for the winter (December–April), spring (May– June), summer (July–September), and autumn (October–November) seasons for the period 1950-2018 are considered. The presence of negative linear trends and the polycyclic oscillations of the ice coverage variability for all seasons has been confirmed. Using spectral analysis, the dominant fluctuations from 5 to 22 years were identified. The cross-correlation method allowed us to determine the significant relationship of the Greenland Sea ice coverage with hydrometeorological and astrogeophysical factors. The statistically significant relationship of the ice coverage for a concrete year with similar characteristics for a previous period persisting up to three years had been noted. The highest cross-correlation coefficients were noted in the winter and spring seasons. The ice coverage of the autumn season demonstrates the persistence of the inertia of ice conditions for up to two years. The analysis of correlations with astrogeophysical parameters revealed the closest relationship between the ice coverage and the longitude coordinate of the Earth's pole position, the nutation parameters of the Earth's axis, and the distance between the Earth and the Sun. When constructing the multi-regression equations, we investigated the informativeness of various hydrometeorological and astrogeophysical factors in the models of the ice coverage variability for each season. The following estimates of quality of the models were obtained: correlation coefficients (up to 0.89), determination coefficients (to up 0.80), and a model reliability which depends on the admissible forecast error and includes the mean square deviation of the investigated value) – up to 99%). The informativeness of various factors was estimated and the contribution to the total variance was revealed: hydrometeorological factors – up to 70%; astrogeophysical factors – up to 50%. The obtained statistical equations can be used for the diagnosis and for development of methods for the very-long-term forecast of the Greenland Sea ice coverage.Подтверждены отрицательные линейные тренды и полицикличность ледовитости Гренландского моря. Установлена тесная связь изменения ледовитости с температурой воздуха и индексами атмосферной циркуляции, а также с долготной координатой положения полюса Земли, параметрами нутации оси Земли и расстоянием между Землей и Солнцем. Получены физико-статистические уравнения изменения ледовитости для всех сезонов с учётом влияния различных факторов и оценена их информативность по вкладу каждого фактора в общую дисперсию. На долю гидрометеорологических индексов приходится до 70%, астрогеофизических – до 50%

ОСОБЕННОСТИ СЕЗОННОЙ И МЕЖГОДОВОЙ ИЗМЕНЧИВОСТИ ЛЕДЯНОГО ПОКРОВА ГРЕНЛАНДСКОГО МОРЯ

The results of studies of seasonal and inter-annual variability of the Greenland Sea ice cover are presented for the period from 1950 to 2016. Statistical characteristics of seasonal and inter-annual changes in the ice-covered area were calculated. Three clusters of typical seasonal variability were identified from the whole totality of all seasonal cycles. The first cluster presented a group of seasonal cycles in the period of maximum, the second one – the middle, and the third group – minimum areas of the winter ice cover. The estimates of correlation between changes in the ice areas in winter (February–March) or in summer (August–September) and areas of the following two months of a current year as well as in succeeding years were obtained. Empirical regularity of a variability of the ice cover during the annual cycle was established. This regularity is characterized by an existence of a ‘memory’ in the state of the ice cover, when a prehistory of the ice conditions determines to a certain extent the following phase. Analysis of inter-annual variability of the Greenland Sea ice cover did show a linear negative tendency in both winter and summer ice conditions. One-two year fluctuations were the most pronounced in the spectral density of inter-annual variations in the summer ice conditions. However, fluctuations with a longer period do also exist. With respect to contribution of hydrometeorological factors, the summer ice area is determined: (a) by conditions in the preceding winter, (b) by the atmospheric circulation, and (c) by the influence of warm Atlantic waters (about 20% of the total dispersion). Changes in the winter ice area depend: (a) mainly on the pre-winter state of ices (October–November), (b) on the influence of the Atlantic waters (about 30% of the total dispersion), and (c) on the heat balance and the atmospheric circulation (20% of the total dispersion). The results of this study may be used as a basis for the development of statistical models for analysis and prediction of long-term and climatic changes in the state of the ice cover in the Greenland Sea.Приведены результаты исследований изменчивости ледяного покрова Гренландского моря с 1950 по 2016 г. Проведена классификация внутригодовых циклов изменения площади ледяного покрова, выделены три кластера подобных сезонных циклов, получены линейные отрицательные тренды ледовитости, показывающие значительное уменьшение ледовитости за последние 66 лет

Распределение кислорода и дефицита кислорода в атлантических водах в Евразийском суббассейне Северного Ледовитого океана

The results of hydrochemical study received during drift of SP-34 and SP-35 stations, and also oceanographic supervision in high-latitude Arctic expeditions 2005 and 2007 are presented. Variability of distribution of the dissolved oxygen and apparent oxygen utilization (AOU) in a core of the Atlantic water mass (AWM) in theEurasianBasinis investigated. Distribution of oxygen in a core of AWM is characterized by its almost constant contents in Amundsen andNansenBasinsand over Gakkel Ridge. Vertical distribution of oxygen in hollows is characterized by a minimum in a core of the Atlantic waters.It is shown that there is a relation between the water temperature in the core of AWM and AOU in the studied area — with reduction of water temperature apparent oxygen utilization increases.The smallest AOU is observed in AWM coming fromFramStraittoNansenBasin. Along the Eurasian continental slope AOU in a core of AWM increases, also the greatest its value has return Atlantic waters inAmundsenBasin. The possible scenarios explaining transformation of characteristics of a core of AWM extending along the Lomonosov Ridge are discussed.Apparent oxygen utilization in a core of AWM has significant variations of sizes in Nansen andAmundsenBasinsand unlike the size of the dissolved oxygen which variability is small, can serve as the good indicator of transformation and circulation of the Atlantic waters in theEurasianBasin.Представлены результаты гидрохимических исследований, полученные во время дрейфа станций СП-34 и СП-35, а также океанографических наблюдений в высокоширотных арктических экспедициях 2005 и 2007 гг. Исследована изменчивость растворенного кислорода и дефицита кислорода в ядре атлантической водной массы (АВМ) в Евразийском суббассейне. Распределение кислорода в ядре АВМ характеризуется практически постоянным его содержанием в котловинах Амундсена и Нансена и над хребтом Гаккеля. Вертикальное распределение кислорода в котловинах характеризуется минимумом в ядре атлантических вод.Показано, что в исследуемом районе между температурой воды в ядре АВМ и дефицитом кислорода существует зависимость, а именно: с уменьшением температуры воды дефицит кислорода увеличивается. Наименьший дефицит кислорода наблюдается в АВМ, поступающей из пролива Фрама в котловину Нансена. Вдоль Евразийского материкового склона дефицит кислорода в ядре АВМ увеличивается, и наибольшее его значение имеют возвратные атлантические воды в котловине Амундсена. Обсуждаются возможные сценарии, объясняющие трансформацию характеристик ядра АВМ, распространяющейся вдоль хребта Ломоносова.Дефицит кислорода в ядре АВМ имеет значимые вариации величин в котловинах Нансена и Амундсена и в отличие от величины растворенного кислорода, изменчивость которого невелика, может служить хорошим индикатором трансформации и циркуляции атлантических вод в Евразийском суббассейне

Климатические изменения сезонных и долгопериодных колебаний ледовитости Гренландского и Баренцева морей

The structure of the long-period variability of the ice cover of the Barents and Greenland Seas over a long series of observations from 1930 to 2017 is analyzed. In both seas, there is a significant negative linear trend of ice cover for both the winter and summer seasons. Average for the period of 1950–2016 intra-annual changes in ice coverings demonstrate the conjugacy of the seasonal cycles of the Greenland and Barents Seas, but with certain differences. Three homogeneous groups with a similar character of intra-annual changes in the ice area are identified for each sea. Identified succession in a state of ice cover for 2 years.The conjugacy of changes in the average decadal values of sea ice cover in April and August with the average decadal indices of atmospheric circulation AO, AD, PNA, NAO and the index of the thermal state of the North Atlantic AMO is shown. Spectral analysis of the winter and summer ice cover of the Greenland and Barents Seas for the period 1930–2016 confirmed earlier received cyclical fluctuations of 22, 9–11 and 6–7 years.Cross-correlation analysis established a close relationship between the longitudinal changes in the ice cover and the average annual values of the following astrogeophysical parameters, the longitude coordinate of the Earth pole position Y, the Earth axis nutation indices dEps and dPsi, the Earth rotation speed index lod (length of day), Sun solar activity index (annual Wolf number) , the average for six months, the distance from the Sun to Earth in the summer SX-III and the winter SX-III periods. Significant correlation coefficients are quite large (R = |0,30| – |0,56|) for both seas, comparable to the correlation coefficients between the ice cover and average annual air temperature T, show the reality of the ice cover mediated reaction to changes in astrophysical factors. Statistical equations relating the sea ice cover to hydrometeorological and astrogeophysical factors were obtained by multiple correlation. The overall correlation coefficient varies from R = 0,80 to R = 0,87 AT. The Greenland Sea, the share of astrogeophysical factors in the long-term changes in the ice cover of both the winter and summer seasons exceeded the contribution of hydrometeorological factors by 3–4 times. In the Barents Sea, the contribution to the total dispersion of astrogeophysical factors in the winter period is somewhat less than that of hydrometeorological factors, and in the summer period they exceed only 1.4 times. The authors’ approach opens up the possibility of using it to obtain statistical equations for the diagnosis and forecast of long-term and climatic changes in sea-ice cover.В статье проанализирована структура долгопериодной изменчивости ледяного покрова Баренцева и Гренландского морей за длительные ряды наблюдений. С помощью кластерного анализа для каждого моря выделены несколько однородных групп с близким характером внутригодовых изменений площади льдов. Выявлена преемственность в состоянии ледяного покрова в течение двух лет. Проанализированы временное распределение аномалий относительно тренда изменчивости ледяного покрова и возможные причины формирования периодов преобладания однонаправленных изменений площади льдов. Получены статистические уравнения связи ледовитости с гидрометеорологическими и астрогеофизическими факторами. Определены доли вклада астрогеофизических факторов в долгопериодные изменения ледовитости Баренцева и Гренландского морей, которые демонстрируют существование различия формирования ледового режима в Гренландском и Баренцевом морях

Toward a warmer Arctic Ocean: Spreading of the early 21st century Atlantic Water warm anomaly along the Eurasian Basin margins

We document through the analysis of 2002–2005 observational data the recent Atlantic Water (AW) warming along the Siberian continental margin due to several AW warm impulses that penetrated into the Arctic Ocean through Fram Strait in 1999–2000. The AW temperature record from our long-term monitoring site in the northern Laptev Sea shows several events of rapid AW temperature increase totaling 0.8°C in February–August 2004. We hypothesize the along-margin spreading of this warmer anomaly has disrupted the downstream thermal equilibrium of the late 1990s to earlier 2000s. The anomaly mean velocity of 2.4–2.5 ± 0.2 cm/s was obtained on the basis of travel time required between the northern Laptev Sea and two anomaly fronts delineated over the Eurasian flank of the Lomonosov Ridge by comparing the 2005 snapshot along-margin data with the AW pre-1990 mean. The magnitude of delineated anomalies exceeds the level of pre-1990 mean along-margin cooling and rises above the level of noise attributed to shifting of the AW jet across the basin margins. The anomaly mean velocity estimation is confirmed by comparing mooring-derived AW temperature time series from 2002 to 2005 with the downstream along-margin AW temperature distribution from 2005. Our mooring current meter data corroborate these estimations