Simulated mean climate response to Caspian Sea area change using the Community Earth System Model (CESM1.2.2)

• Main Authors: Koriche, Sifan A, Nandini-Weiss, Sri Durgesh, Prange, Matthias, Singarayer, Joy S, Arpe, K, Cloke, Hannah L, Schulz, Michael, Bakker, Pepijn, Leroy, Suzanne A G, Coe, Michael
• Format: Dataset
• Language: English
• Published: PANGAEA 2020
• Subjects: Area/locality; Binary Object; Binary Object (File Size); Binary Object (Media Type); Caspian Sea; CESM1.2.2 model; Community Earth System Model version 1.2.2 (CESM1.2.2) with Community Atmospheric Model version-5 (CAM5); Drivers of Pontocaspian biodiversity RIse and DEmise; Evaporation; precipitation; PRIDE; subtropical jet; Pacific; Sea ice
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.923110; https://doi.org/10.1594/PANGAEA.923110

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 in the wider northern hemisphere. The Community Earth System Model (CESM1.2.2) is used to simulate the climate of four scenarios: (1) larger than present CS area, (2) current area, (3) smaller than present area, and (4) 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 area 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 region experiences warming with sea ice reduction in winter. Our results also indicate a weakening of the 500-hPa troughs over the northern Pacific with larger CS area. Lastly, we find a thermal response triggers a southward shift of the jet stream in the upper troposphere during summer. Our findings establish that changing CS area results in climate impacts of such scope that CS area variation should be considered for incorporation into climate model simulations, including palaeo and future scenarios.