Surface Temperatures of the Arctic Oceans

• Main Author: Nielsen-Englyst, Pia
• Format: Book
• Language: English
• Published: Technical University of Denmark 2023
• Subjects: /dk/atira/pure/sustainabledevelopmentgoals/climate_action; SDG 13 - Climate Action; Arctic; Sea ice
• Online Access: https://orbit.dtu.dk/en/publications/ba6fac66-3017-476d-8dfc-55a2a496dbc1; https://backend.orbit.dtu.dk/ws/files/339910017/PhD_Thesis-_Pia_NIelsen-Englyst.pdf

The Arctic is warming faster than any other region of the world (known as Arctic amplification) leading to rapid and widespread changes, which transform the Arctic environment with far-reaching consequences. Despite much attention, existing observational datasets, reanalyses and climate models show large uncertainties in Arctic surface temperatures and limited consensus on the magnitude of the Arctic amplification. The difference and uncertainties mainly arise in the Arctic oceans where many clouds, the mix of open water and sea ice, and the sparse in situ network challenge an accurate and absolute surface temperature estimation. Each of these challenges are considered in this PhD study with the overall aim to provide more accurate and consistent sea surface temperature (SST) and sea ice surface temperature (IST) estimates in the Arctic, and thereby improving the understanding, characterization and monitoring of the Arctic warming and amplification. The frequent and persistent cloud cover in the Arctic limits the extent to which SST can be retrieved from thermal infrared satellite sensors. Therefore, this PhD study explores the capability of using passive microwave (PMW) observations to retrieve SST and improve the SST estimates in the Arctic. Multiple PMW SST retrieval algorithms have been developed, analysed and validated and the first European PMW SST climate data record has been generated. To prepare for the future Copernicus Imaging Microwave Radiometer (CIMR) satellite mission, this study also investigates the impact of using different frequency channels in SST retrievals, with promising results for the proposed CIMR constellation. The impact of including the PMW SST observations in the Arctic surface temperature estimation has been evaluated and substantial improvements are seen. The results are expected to become even better in the future with the launch of CIMR, which will enable SST retrievals at lower uncertainties and much closer to the coasts and sea ice. Due to the mix of open ocean and sea ice ...