Climate change is accelerating the warming of mountain glacial systems, leading to increased water fluxes and the enhanced export of glacially-derived sediment and organic matter (OM). Glacial OM represents an aged yet potentially bioavailable carbon pool that differs in composition from OM found in non-glacially sourced waters. Despite its significance, the composition of riverine OM from glacial headwaters to downstream reaches remains poorly understood in the Canadian Rockies. This dataset presents dissolved OM composition data derived from UV-vis spectroscopy including five calculated spectroscopic parameters (a254, S275_295, BIX, HIX, FI) and model outputs from parallel factor analysis of excitation-emission spectra (C1, C2, C3, C4). This data is supplemented with dissolved and particulate organic carbon concentrations and isotopic characteristics, and water isotope data. Data were collected over three summers (2019-2021) before, during, and after glacial ice melt along stream transects spanning 0-100 km downstream of glacial termini on the eastern slopes of the Canadian Rocky Mountains. Samples were obtained from the Bow River, North Saskatchewan River, and Sunwapta-Athabasca River. Paired microbial samples are archived at the NCBI database, under accession number PRJNA995204.

Further funding information:* Campus Alberta Innovates Program, Web: https://www.alberta.ca/campus-alberta-innovation-program, Award: Campus Alberta Innovates Program Chair funding to MPB and SET