The instrumental data shows 7%-20% increase in annual discharge of the major Eurasian rivers like Ob, Yenisei and Lena between 1936 and 2018 (Wang et al. 2021). The trend has been attributed to increased precipitation and permafrost thawing due to the temperature warming (Walvoord, Kurylyk 2016). However, the instrumental data does not provide the longterm scope of the trend. We modeled seasonal discharge from tree rings for the Yenisei River upstream at Kyzyl gauge and found a remarkable 80% upsurge in winter ‘ow (Nov-Apr) over the last 25 years, which is unprecedented in the last 214 years since 1784 (Panyushkina et al. 2021). In contrast, the annual discharge (Oct-Sept) has only a 7% increase over the last 25 years and shows normal range of variability since 1700 (Fig. 1). Water balance modeling with CRU data at the Yenisei upstream indicates a significant discrepancy between decadal variability of the gauged ‘ow and climate data after 1960 (Fig. 1). The long-term buckhound of the changes in regional hydrology is successfully assessed with tree-ring methods. The tree-ring networks in Eurasian cold climates have a great potential to reconstruct spatial pattern of the seasonal runoff and quantify the long-term impact of permafrost degradation on the hydrological regimes in Siberia. We discuss the impact of melting permafrost on the base ‘ow and enrichment of the surface and groundwater interaction at the Yenisei River basin coupled with the warming temperature and, more importantly, forest fires. Recent increase in the frequency, size, and intensity of boreal fires scale s of its impact on hydrology and permafrost in Siberia. This study demonstrates the complexity of hydrological feedback in Siberia to the Arctic Ampli:cation (AA). The adverse impacts of AA have been and will remain the greatest for the health and socioeconomic of people living in the Pan-Arctic and the geopolitics and macroeconomics of the global society.

Polar regions are highly sensitive to climate change. In recent decades, the Arctic has warmed twice as fast as the world average, which has led to a significant loss of ice cover in the Arctic Ocean. The positive feedback from continental hydrology to Arctic warming amplifies perturbations in the climate system in response to changes in heat and freshwater fluxes. As the surface warms and storm paths change, precipitation and glacier melt have increased pan-Arctic runoff. Melting permafrost adds even more water to river systems. Our research aims to understand 1) whether this feedback impacts the river flow only in the warm season, 2) whether the runoff change in the cold (winter) season can amplify the initial warming, and 3) what is the spatiotemporal pattern of seasonal variations in streamflow across pan-Arctic watersheds. Tree rings serve as critical proxies for quantifying hydrological responses to climate change. We are exploring the potential of modeling seasonal flows, especially winter versus spring and summer flows, and water temperature using intra-seasonal aggregation of climate signals in subsets of ring chronologies derived from quantified tracheal cell parameters: cell area, tangential cell diameter, radial cell diameter, cell wall thickness. The preliminary results demonstrate significant correlation of summer water temperature with cell area and radial cell diameter, whereas the discharge correlates stronger with cell wall thickness and tangential cell diameter. We emphasize the importance of modeling intra-seasonal hydrological parameters versa the hydrological year average to analyze the contribution of continental hydrology to Arctic warming.

Recent, record-breaking discharge in the Yenisei River, Siberia, is part of a larger trend of increasing river flow in the Arctic driven by Arctic amplification. These changes in magnitude and timing of discharge can lead to increased risk of extreme flood events, with implications for infrastructure, ecosystems, and climate. To better understand the changes taking place, it is useful to have records that help place recent hydrological changes in context. In addition to an existing network of river gauges, extreme flood events can be captured in the wood anatomical features of riparian trees, which help identify the most extreme flood events. Along the Yenisei River, Siberia we collected willow (Salix spp.) samples from a low terrace that occasionally floods when water levels are extremely high. Using these samples, we use an approach known as quantitative wood anatomy to measure variation in radial cell dimensions, including vessel area, wood fiber size and cell wall thickness. We then compare these measurements to observed records of flood stage. We hypothesize that (1) characteristic patterns of wood fiber size and cell wall thickness in Salix rings are present during flood years, (2) these patterns can be quantified by measuring wood fiber size and cell wall thickness, and (3) quantified variations in cell anatomical properties can be related to flood magnitude and duration. Understanding how riparian vegetation responds to extreme flood events can help us better manage riparian ecosystems and understand changes to the Arctic hydrological regime.

Recent, record-breaking discharge in the Yenisei River, Siberia, is part of a larger trend of increasing river flow in the Arctic driven by Arctic Amplification (AA). These changes in magnitude and timing of discharge can lead to increased risk of extreme flood events, with implications for infrastructure, ecosystems, and climate. To better understand the changes taking place, it is useful to have records that help place recent hydrological changes in context. In addition to an existing network of river gauges, wood anatomical features in riparian trees have been shown to record extreme flooding. Along the lower reaches of the Yenisei River we collected white willow (Salix alba) samples from a fluvial fill flat terrace that occasionally floods when water levels are extremely high. At the end of certain annual growth rings these samples displayed terminal white bands, a type of intra-annual density fluctuation (IADF). To identify the characteristics and causes of these features we use an approach known as quantitative wood anatomy (QWA) to measure variation in fiber cell dimensions across tree rings, particularly fiber lumen area (LA) and cell wall thickness (CWT). We investigate (1) which cell parameters and method to extract intra-annual data from annual tree rings best capture terminal white bands identified in Salix, and (2) if these patterns are related to flood magnitude and/or duration. We find that fiber CWT best captures the IADFs found in Salix rings. For some trees, time series of normalized CWT correlate with July flood durations, which have changed since the 1980s. Understanding how riparian vegetation responds to extreme flood events can help us better manage riparian ecosystems and understand changes to the Arctic hydrological regime.

Due to the effects of climate change, the USA Southwest is expected to experience increased temperatures and decreased water availability. Extended droughts will likely have important consequences for riparian trees whose growth and habitat are strongly limited by water availability. One consequence of extended water table declines on riparian trees is the development of wood anatomical anomalies. Using techniques developed for quantitative wood anatomy (QWA) it may be possible to quantify these anomalies and reconstruct water table variability through time. We explore this possibility using tree rings from netleaf hackberry (Celtis laevigata var. reticulata) collected along the Upper Santa Cruz River, Arizona. We suggest hackberry has the potential to be used 1) as an indicator of riparian ecosystem health, and 2) to provide improved reconstructions of water availability. Understanding how hackberry responds to periods of low and high flows can provide insight into how to better manage these ecosystems into the future.