Seasonal variability in pathways of warm-water masses toward the Kangerdlugssuaq Fjord (KF)–Glacier (KG) system, southeast Greenland, is investigated by backtracking Lagrangian particles seeded at the fjord mouth in a high-resolution regional ocean model simulation in the ice-free and the ice-covered seasons. The waters at KF are a mixture of Atlantic-origin water advected from the Irminger Basin [Faxaflói (FF)], the deep waters from the Denmark Strait, and the waters from the Arctic Ocean, both represented by the Kögur section (KO). Below 200-m depth, the warm water is a mixture of FF and KO water masses and is warmer in winter than in summer. The authors find that seasonal differences in pathways double the fraction of FF particles in winter, causing the seasonal warming and salinification. Seasonal temperature variations at the upstream sections (FF and KO) have a negligible impact on temperature variations near the fjord. Successful monitoring of heat flux to the fjord therefore needs to take place close to the fjord and cannot be inferred from upstream conditions.@en