Modelling impacts of extreme Caspian Sea area change on hydroclimatic processes
Abstract
The Caspian Sea is the largest inland lake in the world and has experienced extreme sea level variations of up to 150 m ever since its existence. This variation can result in enormous surface area change, more than the size of Netherlands and Belgium combined, which can affect regional and large-scale processes. In this study, we investigate how changes in Caspian Sea area drive regional and large-scale climate patterns. To achieve this, we consider four scenarios of different Caspian Sea size including its current modelled state (0.72 Mkm2; sea level equal to the global m.s.l.), its current observed state (0.42 Mkm2; 27 meters below m.s.l.), its smaller state (0.17 Mkm2; 90 meters below m.s.l.) and a fully dried scenario using the state-of-the-art coupled general circulation earth system model CESM1.2.2. Equilibrium simulations of pre-industrial conditions are run for 100 years and the last 50 years are taken for analysis in our sensitivity study. Our findings show that the variation of Caspian Sea area has a strong influence on regional atmospheric water budget. Both precipitation and evaporation increase with bigger Caspian Sea area with up to a 398% increase in mean annual evaporation for large Caspian Sea with respect to a no-Caspian Sea scenario. Change in surface temperature (2 m) is also significant with changing Caspian Sea area. The large-scale circulation impacts for all scenarios also present strong responses in terms of temperature, sub-tropical jet stream, and geopotential height. Our study confirms that reducing the Caspian Sea area impacts upper atmospheric temperatures between winter and summer seasons, leading to a southward shift of the sub-tropical jet stream in the summer. A smaller Caspian Sea area produces changes in tropospheric thermal gradients that trigger the widening of the troughs at 500 hPa as far as the northern Pacific. Our findings establish that varying Caspian Sea surface area results in regional and remote climate impacts of such scope that Caspian Sea variation should be considered for incorporation into global climate model simulations, including paleo and future scenarios.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A53L2669K
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSESDE: 3319 General circulation;
- ATMOSPHERIC PROCESSESDE: 3339 Ocean/atmosphere interactions;
- ATMOSPHERIC PROCESSESDE: 3364 Synoptic-scale meteorology;
- ATMOSPHERIC PROCESSES