The shortness of gaged river flows limits our understanding of the variability of the river component of heat and fresh water inflow to the Arctic Ocean. This talk describes a tree-ring approach to addressing the uncertainty of Arctic river flows using a combination of non-riparian and riparian trees growing in the floodplain of the lower Ob River, in western Siberia. The talk focuses specifically on the tree-ring signal for inter-annual variability of flooding, which happens on a massive spatial scale each year along the Ob with spring ice break. Results using tree-ring samples collected over the past several years by a collaboration of Russian and USA tree-ring researchers shows a species-dependent mix of positive and negative responses of tree-ring width to flooding. The talk addresses modeling approaches to signal identification and to reconstruction of high flows on the Ob, and extension to a more extensive research project now starting on the adjacent Yenisei River Basin.