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1. Controls of Variability in the Laurentian Great Lakes Terrestrial Water Budget

   https://doi.org/10.1029/2022WR033759  

   Minallah, Samar; Steiner, Allison_L; Ivanov, Valeriy_Y; Wood, Andrew_W (October 2023, Water Resources Research)

   Abstract The land surface hydrology of the North American Great Lakes region regulates ecosystem water availability, lake levels, vegetation dynamics, and agricultural practices. In this study, we analyze the Great Lakes terrestrial water budget using the Noah‐MP land surface model to characterize the catchment hydrological regimes and identify the dominant quantities contributing to the variability in the land surface hydrology. We show that the Great Lakes domain is not hydrologically uniform and strong spatiotemporal differences exist in the regulators of the hydrological budget at daily, monthly, and annual timescales. Subseasonally, precipitation and soil moisture explain nearly all the terrestrial water budget variability in the southern basins, while the northern latitudes are snow‐dominated regimes. Seasonal assessments reveal greater differences among the basins. Precipitation, evaporation, and runoff are the dominant sources of variability at lower latitudes, while at higher latitudes, terrestrial water storage in the form of ground snowpack and soil moisture has the leading role. Differences in land cover categorizations, for example, croplands, forests, or urban zones, further induce spatial differences in the hydrological characteristics. This quantification of variability in the terrestrial water cycle embedded at different temporal scales is important to assess the impacts of changes in climate and land cover on catchment sensitivities across the diverse hydroclimate of the Great Lakes region. 

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2. Arctic Tundra Lake Drainage Increases Snow Storage in Drifts

   https://doi.org/10.1029/2023JF007294  

   Rangel, R. C.; Ohara, N.; Parsekian, A. D.; Jones, B. M. (September 2023, Journal of Geophysical Research: Earth Surface)

   Abstract Snowdrifts formed by wind transported snow deposition represent a vital component of the earth surface processes on Arctic tundra. Snow accumulation on steep slopes particularly at the margins of rivers, coasts, lakes, and drained lake basins (DLBs) comprise a significant water storage component for the ecosystem during spring and summer snowmelt. The tundra landscape is in constant change as lakes drain, substantially altering the surface morphology that partially controls how snow drifts and accumulates throughout the cold seasons. Here, we combine field measurements, remote sensing observations, and snow modeling to investigate how lake drainage affects snow redistribution at Inigok on the Arctic Coastal Plain of Alaska, where the snow movement is controlled by wind. Field observations included measurements of snow depth using ground penetrating radar and probe. We mapped mid‐July snow cover and modeled snow redistribution before and after drainage simulation for 33 lakes (∼30 km²) in our study area (∼140 km²). Our results show the advantage of using a wide range of snow depth measurements on frozen lakes, DLBs, and upland to validate the snow modeling in order to capture the variability inherent in the landscape. The lake drainage simulation suggests an increase in snow storage of up to ∼24% at DLBs compared to extant lakes, ∼35% considering only snowdrifts (assumed as ≥1 m depth), and ∼4% considering the whole study area. This increase in snow accumulation could significantly impact the landscape when it melts, including wildlife, vegetation, biogeochemical processes, and potential natural hazards like snow‐dam outburst floods. 

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3. Stormwater runoff microplastics: Polymer types, particle size, and factors controlling loading rates

   https://doi.org/10.1016/j.scitotenv.2024.172485  

   Ochoa, Lilia; Chan, Julianne; Auguste, Caitlyn; Arbuckle-Keil, Georgia; Fahrenfeld, NL (June 2024, Science of The Total Environment)

   Stormwater runoff is a pathway of entry for microplastics (MPs, plastics <5 mm) into aquatic ecosystems. The objectives of this study were to determine MP size, morphology, chemical composition, and loading across urban storm events. Particles were extracted from stormwater samples collected at outfall locations using wet peroxide oxidation and cellulose digestion followed by analysis via attenuated total reflectance (ATR) FTIR. Concentrations observed were 0.99 ± 1.10 MP/L for 500–1000 μm and 0.41 ± 0.30 MP/L for the 1000–5000 μm size ranges. Seventeen different polymer types were observed. MP particle sizes measured using a FTIR-microscope camera indicated non-target size particles based on sieve-size classification, highlighting a potential source of error in studies reporting concentration by size class. A maximum MP load of 38.3 MP/m2 of upstream catchment was calculated. MP loadings had moderate correlations with both rainfall accumulation and intensity (Kendall τ = 0.54 and 0.42, respectively, both p ≤ 0.005). First flush (i.e. rapid wash-off of pollutants from watershed surfaces during rainfall early stages) was not always observed, and antecedent dry days were not correlated with MP abundance, likely due to the short dry periods between sampling events. Overall, the results presented provide data for risk assessment and mitigation strategies. 

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4. Microplastics in the Mississippi River System during Flash Drought Conditions

   https://doi.org/10.3390/environments11070141  

   Wontor, Kendall; Olubusoye, Boluwatife S; Cizdziel, James V (July 2024, Environments)

   The Mississippi River System is of great ecological and economic importance, making it crucial to monitor contaminants within it. While nutrient pollution is well studied, there are little data on microplastics (MPs) in the Mississippi River System (MSRS), especially during drought conditions. Herein, we characterize MP pollution from seven sites across the MSRS during both flash drought and non-drought periods using FTIR microspectroscopy (µ-FTIR). Additionally, we evaluate the impact of multiple water level conditions on MP polymer composition across five time points at a single sampling site. Of all MPs identified, polyethylene terephthalate (PET, 22%), resin (17%), and polyethylene (PE, 10%) were the most abundant polymers. Average concentrations ranged from 16 to 381 MPs/L across seven sites, with no significant difference in concentration between conditions. Irregular particles were the most common morphology, with most MPs falling in the lowest size range measured (30–100 μm). Drought condition had a significant (p < 0.001) impact on polymer composition, and polymers most strongly correlated with flash drought were mostly fluoropolymers. For the single sampling site, concentrations differed, but not significantly, across the five timepoints. These results demonstrate the complex relationship between MP concentration and drought condition, and also highlight the importance of fully characterizing MPs in environmental studies. 

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5. Patterns and Drivers of Carbon Dioxide Concentrations in Aquatic Ecosystems of the Arctic Coastal Tundra

   https://doi.org/10.1029/2020GB006552  

   Lougheed, V. L.; Tweedie, C. E.; Andresen, C. G.; Armendariz, A. M.; Escarzaga, S. M.; Tarin, G. (March 2020, Global Biogeochemical Cycles)

   Abstract Multiple aquatic ecosystems (pond, lake, river, lagoon, and ocean) on the Arctic Coastal Plain near Utqiaġvik, Alaska, USA, were visited to determine their relative atmospheric CO₂flux and how this may have changed over time. The nearshore coastal waters and large freshwater lakes were small sources of atmospheric CO₂, whereas smaller waterbodies were substantial sources.pCO₂was linked to dissolved organic carbon concentrations across broad spatial and temporal scales, with greater concentrations found in smaller freshwater systems (i.e., ponds and rivers). On a day‐to‐day basis, water temperatures appeared to be the strongest driver ofpCO₂levels in tundra ponds, where warmer temperatures likely stimulated microbial mineralization of carbon in both aquatic and hydrologically linked terrestrial environments. Large rainfall events, which may lead to inflow of carbon‐rich groundwater into these ponds, also were associated with increased daily averagepCO₂. Based on comparison to historical data, we estimate that CO₂concentrations in tundra ponds have increased more than 1.8 times over the past 40 years. Quantifying CO₂flux from these abundant aquatic ecosystems on the Arctic Coastal Plain and elsewhere in the high northern latitudes will likely have important implications for furthering understanding of landscape‐level and nearshore carbon dynamics in the Arctic. 

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