Long-term evolution of Caspian Sea thermohaline properties reconstructed in an eddy-resolving ocean general circulation model

Dyakonov, G. S.; Ibrayev, R. A.

doi:10.5194/os-15-527-2019

Cited by 11 publications

(9 citation statements)

References 21 publications

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“…Furthermore, the circulation patterns of the Caspian Sea itself have not been considered in this study. However, the Caspian Sea has three zones of circulation due to the slightly saline water, the shape of the lake (bathymetry and elongated surface area in the north‐south direction) and locations of riverine input (Dyakonov & Ibrayev, 2019; Leroy et al., 2020). Circulation in the sea is both wind‐driven and thermohaline (density‐driven) in nature.…”

Section: Discussionmentioning

confidence: 99%

Impacts of Variations in Caspian Sea Surface Area on Catchment‐Scale and Large‐Scale Climate

et al. 2021

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The Caspian Sea (CS) is the largest inland lake in the world. Large variations in sea level and surface area occurred in the past and are projected for the future. The potential impacts on regional and large-scale hydroclimate are not well understood. Here, we examine the impact of CS area on climate within its catchment and across the northern hemisphere, for the first time with a fully coupled climate model. The Community Earth System Model (CESM1.2.2) is used to simulate the climate of four scenarios: (a) larger than present CS area, (b) current area, (c) smaller than present area, and (d) no-CS scenario. The results reveal large changes in the regional atmospheric water budget. Evaporation (e) over the sea increases with increasing area, while precipitation (P) increases over the south-west CS with increasing area. P-E over the CS catchment decreases as CS surface area increases, indicating a dominant negative lake-evaporation feedback. A larger CS reduces summer surface air temperatures and increases winter temperatures. The impacts extend eastwards, where summer precipitation is enhanced over central Asia and the north-western Pacific experiences warming with reduced winter sea ice. Our results also indicate weakening of the 500-hPa troughs over the northern Pacific with larger CS area. We find a thermal response triggers a southward shift of the upper troposphere jet stream during summer. Our findings establish that changing CS area results in climate impacts of such scope that CS area variations should be incorporated into climate model simulations, including palaeo and future scenarios. Plain Language SummaryThe Caspian Sea is the largest land-locked water body in the world. It is filled by rivers draining a vast region from northern Russia to Iran. The size of the Caspian Sea has varied considerably over recent centuries and millennia due to various factors, including changes in climate. Conversely, as the area of the sea changes it also has impacts on the climate, but there are significant questions about how and where those impacts would be felt. In this study we used a stateof-the-art climate model in which we specified different sizes of Caspian Sea in order to examine how the climate changes as its area increases. We observed that the local seasonal cycle of temperatures gets smaller, and evaporation increases, while there are more spatially complex changes in local rainfall. Furthermore, the impacts on atmospheric circulation occur as far as the north Pacific, with resulting increases in temperature and decreases in sea-ice coverage in winter as the Caspian area increases. The climate impacts are so significant and geographically extensive that climate models used to simulate climate change (both in future and past scenarios) should incorporate changes to the Caspian Sea area if they are to robustly model regional climate. KORICHE ET AL.

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Section: Discussionmentioning

confidence: 99%

Impacts of Variations in Caspian Sea Surface Area on Catchment‐Scale and Large‐Scale Climate

et al. 2021

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“…As indicated by Dyakonov and Ibrayev [58], the northern region of the Caspian Sea is shallow, with a maximum depth of about 40 m, while the middle and southern regions are strongly deeper, as testified by a peak depth of about 1025 m.…”

Section: Study Sitementioning

confidence: 72%

On the Indirect Estimation of Wind Wave Heights over the Southern Coasts of Caspian Sea: A Comparative Analysis

Lama

Sadeghifar

Azad

et al. 2022

Water

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The prediction of ocean waves is a highly challenging task in coastal and water engineering in general due to their very high randomness. In the present case study, an analysis of wind, sea flow features, and wave height in the southern coasts of the Caspian Sea, especially in the off-coast sea waters of Mazandaran Province in Northern Iran, was performed. Satellite altimetry-based significant wave heights associated with the period of observation in 2016 were validated based on those measured at a buoy station in the same year. The comparative analysis between them showed that satellite-based wave heights are highly correlated to buoy data, as testified by a high coefficient of correlation r (0.87), low Bias (0.063 m), and root-mean-squared error (0.071 m). It was possible to assess that the dominant wave direction in the study area was northwest. Considering the main factors affecting wind-induced waves, the atmospheric framework in the examined sea region with high pressure was identified as the main factor to be taken into account in the formation of waves. The outcomes of the present research provide an interesting methodological tool for obtaining and processing accurate wave height estimations in such an intricate flow playground as the southern coasts of the Caspian Sea.

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“…Расчет течений выполнен по модели, описанной в [9], которая ранее применялась для исследования климатических изменений уровня и термохалинной структуры Каспийского моря [10,13]. Горизонтальное разрешение составляет 2 км, что достаточно для описания мезомасштабной динамики вод: в Каспийском море бароклинный радиус деформации Россби оценивается в 17-22 км в глубоководных районах и в 3-8 км на шельфе в восточной части Среднего Каспия [14].…”

Section: численный экспериментunclassified

Dynamics of the Caspian Sea Waters over the Apsheron Sill in 2003

Dyakonov¹,

Ibrayev²

2019

MGZh

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The paper is aimed at studying water exchange between the Middle and South Caspian, at assessing its intensity, spatial-temporal structure and variability. Methods and Results. The study includes the numerical model of the Caspian Sea general circulation; it is of sufficiently high resolution for reproducing mesoscale structure of the currents-2 km. Due to the model, the Caspian Sea circulation in 2003 was reconstructed and the basic characteristics of water transfer between the Middle and the South Caspian were calculated. This specific year was chosen since in all its months, the wind fields in the Middle and South Caspian water areas were in good agreement with the average climatic ones. The simulated structure of the currents over the Apsheron Sill represents the following pattern: the northward currents are most often formed over the eastern shelf slopes, and the southward onesover the western shelf slope. The latter are usually more intense and regular. From mid July to October, the easterly winds regularly occur over the Caspian Sea strengthening the northward currents, which, in their turn, transfer relatively salty and warm waters of the South Caspian to its Middle regions along the eastern coast. A fairly stable southward stream resulted from the density gradient between the cold Middle and the warm South Caspian, is located along the western shelf slope at the depths 100-150 m. On the whole, the water flow above the sill is directed from north to south. At that the southward flows are distributed rather evenly throughout the year, whereas the major part of the northward currents' flow is observed from late July to December. Conclusions. Since the South Caspian waters on all the depths are warmer and more salty than those in the Middle regions, water exchange between two basins in course of the whole year, contributes to increase both of temperature and salinity in the Middle Caspian, and to their decrease in the South Caspian, respectively. The current-originated salt flows in the region are sufficient to make salinity grow in the Middle Caspian upper layer by 0.5 psu within 100 days, at that the corresponding temperature increase does not exceed 0.01-0.03°C per day. The reverse southward currents transfer relatively fresh water to the South Caspian that lowers salinity of its upper layer by 0.2 psu per month. However, such intense intrusions are noted only in March and December. The impact of these currents on the South Caspian heat balance is more uniform throughout the year and does not exceed 0.17°C/day.

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Long-term evolution of Caspian Sea thermohaline properties reconstructed in an eddy-resolving ocean general circulation model

Cited by 11 publications

References 21 publications

Impacts of Variations in Caspian Sea Surface Area on Catchment‐Scale and Large‐Scale Climate

Impacts of Variations in Caspian Sea Surface Area on Catchment‐Scale and Large‐Scale Climate

On the Indirect Estimation of Wind Wave Heights over the Southern Coasts of Caspian Sea: A Comparative Analysis

Dynamics of the Caspian Sea Waters over the Apsheron Sill in 2003

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