Rapid changes in the Arctic significantly impact the characteristics of water masses in the Arctic Ocean, potentially affecting the ocean's physical and biogeochemical processes. This study utilizes the latest MOSAiC observation data (from October 2019 to August 2020) and high-resolution reanalysis data (GLORYS12V1) to analyze the variations in temperature and salinity of water masses across the Eurasian Basin along the MOSAiC drift trajectory, and to explore the influence of the Atlantic inflow on these variations.

The results show that: (1) Both temperature and salinity within the upper 100 m layer along the drift trajectory exhibit an overall pattern of initially increasing and then decreasing from the Amundsen Basin to the Nansen Basin. The spatial variation in salinity is greatest within the 0-20 m layer, with highly saline surface water (S >34) present in Nansen Basin. In contrast, the variation in temperature is greatest at the 100 m layer, with the depth of 0°C isothermal less than 100 m in parts of the Nansen Basin. Although GLORYS12V1 simulates the higher temperature in the upper Nansen Basin, it reasonably captures the main features of horizontal and vertical variations in temperature and salinity along the drift trajectory. (2) The warm and saline Atlantic water generally flows anticlockwise in the Eurasian Basin, with its depth gradually deepening during transport, which predominantly determines the overall variations in temperature and salinity in intermedia and upper layers in the Eurasian Basin. The saline surface water in the western Nansen Basin is due to the drift trajectory involved into the regions influenced by deep winter convection in the northern Svalbard. Strong wind events play a limited role in the variations in temperature and salinity along the drift trajectory. (3) In the western Nansen Basin, GLORYS12V1 indicates a northward extension of Atlantic Water at the 100 m layer , with its northern boundary nearing the Gakkel Ridge beyond what is observed. This discrepancy results in an overestimation of temperature compared to in-situ observations. To improve the accuracy of the GLORYS12V1 reanalysis results, refining the setting of Atlantic inflow flux at the boundary is suggested.