Irina Overeem’s research while affiliated with University of Colorado Boulder and other places

Artificial lakes (reservoirs) accumulate sediment and organic carbon (OC) over time. We investigated sedimentation processes in a dryland reservoir and informed OC burial and potential preservation. Our study site, Elephant Butte Reservoir on the Rio Grande, New Mexico, USA receives inflows from sediment‐laden, monsoon‐driven flash floods. Using field data, historical reservoir sedimentation survey and river flux (water, sediment, and OC) data, we estimated sedimentation and carbon burial volumes and rates within the delta, reservoir bottom, and whole reservoir during wet (1980–1988) and dry (2007–2017/2019) climate periods. During severe drought (2021–2022), we measured suspended sediment and OC concentrations for characteristic (seasonal) phases of the river hydrograph, monitored delta sedimentation patterns, and observed river outflow plume dynamics. Measured suspended sediment concentrations (mean = 8,818 mg/l, median = 1,769 mg/l) frequently surpassed the hyperpycnal plume threshold (1,000 mg/l), especially during flash floods (maximum = 46,718 mg/l). River total OC content averaged 5.2% ± 12.2%, increasing to 6.3% ± 10.3% in the summer. Whole reservoir linear sedimentation averaged 3.1 ± 1.4% (dry)–4.0 ± 4.2% (wet) cm/yr, with higher rates on the reservoir bottom (5.0 ± 0.3% cm/yr) than the delta (0.8 ± 1.1% cm/yr) during drought from hyperpycnal plume deposition, potentially preserving OC. Comparisons of OC content in suspension and deposited OC in the delta indicate partial OC preservation. Estimated whole reservoir OC burial is higher during dry than wet conditions (391 ± 43.6% vs. 82.4 ± 56.4% g C/m²yr), suggesting that dryland reservoirs may be efficient carbon sinks during these periods.

Investigating erosion and river sediment yield in high-mountain areas is crucial for understanding landscape and biogeochemical responses to environmental change. We compile data on contemporary fluvial suspended sediment yield (SSY) and 12 environmental proxies from 151 rivers in High Mountain Asia surrounding the Tibetan Plateau. We demonstrate that glaciers exert a first-order control on fluvial SSYs, with high precipitation nonlinearly amplifying their role, especially in high–glacier cover basins. We find a bidirectional response to vegetation’s influence on SSY in the Eastern Tibetan Plateau and Tien Shan and identify that the two interacting factors of precipitation and vegetation cover explain 54% of the variability in SSY, reflecting the divergent roles of vegetation in promoting biogenic-weathering versus slope stabilization across bioclimatic zones. The competing interactions between glaciers, ecosystems, and climate in delivering suspended sediment have important implications for predicting carbon and nutrient exports and water quality in response to future climate change.

Sediment erosion, transport, and deposition by glaciers and ice sheets play crucial roles in shaping landscapes, provide important nutrients to downstream ecosystems, and preserve key indicators of past climate conditions in the geologic record. While previous work has quantified sediment fluxes from subglacial meltwater, we also observe sediment entrained within basal ice, transported by the flow of the glacier itself. However, the formation and evolution of these debris‐rich ice layers remains poorly understood and rarely represented in landscape evolution models. Here, we identify a characteristic sequence of basal ice layers at Mendenhall Glacier, Alaska. We develop a numerical model of frozen fringe and regelation processes that describes the co‐evolution of this sequence and explore the sensitivity of the model to key properties of the subglacial sedimentary system, using the Instructed Glacier Model to parameterize ice dynamics. Then, we run numerical simulations over the spatial extent of Mendenhall Glacier, showing that the sediment transport model can predict the observed basal ice stratigraphy at the glacier's terminus. From the model results, we estimate basal ice layers transport between 23,300 m3 ${\mathrm{m}}^{3}$ a−1 ${\mathrm{a}}^{-1}$ and 39,800 m3 ${\mathrm{m}}^{3}$ a−1 ${\mathrm{a}}^{-1}$ of sediment, mostly entrained in the lowermost ice layers nearest to the bed, maximized by high effective pressures and slow, convergent flow fields. Overall, our results highlight the role of basal sediment entrainment in delivering eroded material to the glacier terminus and indicate that this process should not be ignored in broader models of landscape evolution.

Permafrost holds more than twice the amount of carbon currently in the atmosphere, but this large carbon reservoir is vulnerable to thaw and erosion under a rapidly changing Arctic climate. Convective storms are becoming increasingly common during Arctic summers and can amplify runoff and erosion. These extreme events, in concert with active layer deepening, may accelerate carbon loss from the Arctic landscape. However, we lack measurements of carbon fluxes during these events. Rivers are sensitive to physical, chemical, and hydrological perturbations, and thus are excellent systems for studying landscape responses to thunderstorms. We present observations from the Canning River, Alaska, which drains the northern Brooks Range and flows across a continuous permafrost landscape to the Beaufort Sea. During summer 2022 and 2023 field campaigns, we opportunistically monitored river discharge, sediment, and organic carbon fluxes during several thunderstorms. During one notable storm, river discharge nearly doubled from ~130 m 3 /s to ~240 m 3 /s, suspended sediment flux increased 70-fold, and the particulate organic carbon (POC) flux increased 90-fold relative to non-storm conditions. Taken together, the river exported ~16 metric tons of POC over one hour of this sustained event, not including the additional flux of woody debris. Furthermore, the dissolved organic carbon (DOC) flux nearly doubled. Although these thunderstorm-driven fluxes are short-lived (hours to days), they play an outsized role in exporting organic carbon from Arctic rivers. Understanding how these extreme events impact river water, sediment, and carbon dynamics will help predict how Arctic climate change will modify the global carbon cycle.

The contribution of river corridors to the global carbon budget exceeds their small areal footprint, yet our understanding of fluvial carbon dynamics is incomplete, particularly in periglacial settings. Frequent disturbance and lateral fluxes are key attributes of carbon budgets in riparian corridors. Climate change affects the pace and style of fluvial and biogeochemical processes in periglacial settings. The effects of these can be assessed with a carbon budget, a statement of all fluxes in and out of a control volume, which we outline for a river corridor. We are generating data from a field campaign of the carbon stock in select river corridor segments of the Canning River, Alaska. This gravel-bedded river drains continuous permafrost from glaciated headwaters in the Brooks Range to its delta in the Beaufort Sea. Fluvial erosion and deposition generate distinct, mappable geomorphic surfaces in the river corridor that accumulate carbon over time. Carbon stocks on surfaces are summed across the river corridor to compute the total carbon stock. Characterizing the depth of alluvium is a poorly constrained component of the carbon stock. Lateral bank erosion hews away geomorphic surfaces, while sediment deposition buries carbon and generates new surfaces. Deposition of uprooted willows or turf mats augment the carbon stock and can jump-start plant succession. All fluxes in the carbon budget are sensitive to warming and arctic hydrologic intensification. Analyzing how these fluxes may change and affect the carbon stock in icy river corridors will advance our understanding of their contribution to the global carbon budget.

Deltas are threatened by erosion due to climate change and reduced sediment supply, but their response to these changes remains poorly quantified. We investigate the abandoned Yellow River delta that has transitioned from rapid growth to ongoing deterioration due to a river avulsion removing the sediment supply. Integrating bathymetric data, process observations, and sediment transport modeling, we find that while the subaerial delta was stabilized by engineering measures, the subaqueous delta continued to erode due to intensified storms, losing 39% of its mass deposited before the avulsion. Long-term observations show that winter storms initiate scouring of the subaqueous delta, contributing up to 70% of seabed erosion. We then analyze 108 global deltas to assess subaqueous delta erosion risks and identify 17 deltas facing similar situations of sediment decline and storm intensification during the past 40 years. Our findings suggest that subaqueous delta erosion must be integrated into delta sustainability evaluations.

Progress in better understanding and modeling Earth surface systems requires an ongoing integration of data and numerical models. Advances are currently hampered by technical barriers that inhibit finding, accessing, and executing modeling software with related datasets. We propose a design framework for Data Components, which are software packages that provide access to particular research datasets or types of data. Because they use a standard interface based on the Basic Model Interface (BMI), Data Components can function as plug-and-play components within modeling frameworks to facilitate seamless data–model integration. To illustrate the design and potential applications of Data Components and their advantages, we present several case studies in Earth surface processes analysis and modeling. The results demonstrate that the Data Component design provides a consistent and efficient way to access heterogeneous datasets from multiple sources and to seamlessly integrate them with various models. This design supports the creation of open data–model integration workflows that can be discovered, accessed, and reproduced through online data sharing platforms, which promotes data reuse and improves research transparency and reproducibility.