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X-Ray Diffraction (XRD) analysis of streambed sediments:\n\nWe investigated the mineral composition of the particle size fraction < 63 µm (silt and clay fraction) of streambed sediments collected within the Brøggerbreen, Midtre and Austre Lovénbreen catchments by X-Ray Diffraction (XRD) analysis. The samples were collected in July 2020, dried and sieved. The measurements were performed at the University of Bremen (Germany) using a Philips X’Pert Pro diffractometer equipped with a Cu‐tube and a monochromator following the method by Vogt (2009). We evaluated the data using the QUAX full-pattern analysis software (Vogt et al., 2002) for semiquantitative determination of the major mineral composition.\n\nRadiochemical analysis of sediment cores:\n\nSediment cores were collected at 4 sites PN, IA, F, and V in Kongsfjorden, Svalbard, July 28 – 30, 2021.  Gamma activities of 234Th, 7Be, 210Pb, 226Ra and 137Cs  in core sections were measured in the radiochemistry lab (Prof. J.K. Cochran; Director) at the School of Marine and Atmospheric Sciences, Stony Brook University. Samples from sectioned cores were dried at 75°C.  Gamma activities were measured using Canberra planar intrinsic germanium gamma detectors as follows: 234Th (63 keV) activities were counted shortly after collection and then recounted 6 months later to determine the supported activity (238U) or in some cases by using the average 234Th activity from multiple intervals at depth in the same core.    7Be (477 keV) activities were measured in the initially counted samples.  Corrections were made for self-absorption of gamma radiation by samples as a function of sample mass and counting geometry (Cochran et al., 1998).  It is possible that corrections for geometries may change slightly based on subsequent study so that reported activities are subject to possible updates. \n\nThese data are dicussed and cited in:\n\nLaura M. Wehrmann, Robert C. Aller, Sabine Kasten, Jack Dotzler  and Grit Steinhoefel.   Rapid forward and reverse weathering reactions drive cryptic silica and cation cycling in Arctic fjord sediments. Global Biogeochemical Cycles.  2025"]}