The Department of Geosciences is a result of the merger of the Geography and Geology & Geophysics Departments, effective July 2014.

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  • Geochemical Weathering Variability in High Latitude Watersheds

    Jenckes, Jordan (Wiley, 2023)
    High latitude regions across the globe are undergoing severe modifications due to changing climate. A high latitude region of concern is the Gulf of Alaska (GoA) where these changes in hydroclimate undoubtedly effect the hydrogeochemistry of freshwater discharging to the nearshore ecosystems of the region. To fill the knowledge gap of our understanding of freshwater stream geochemistry with the GoA, we compile stream water chemistry data from 162 stream sites across the region. With an inverse model we estimate fractional contributions to solute fluxes from weathering of silicate, carbonate, and sulfide minerals, and precipitation. We asses weathering rates across the region and compare against global river yields. Median fractional contribution of carbonate weathering to total weathering products is 78% across all stream sites, however, there are several streams where silicate weathering is a dominant source of solutes. Weathering by sulfuric acid is elevated in glacierized watersheds. Finally, cation weathering rates are lower in GoA streams compared to the world’s largest rivers, however, weathering rates are similar when compared to a global dataset of glacier fed streams. Due to the climate sensitivity of chemical weathering, we expect future changes to the hydrogeochemistry of river water flux to nearshore ecosystems. We suggest that hydrologic changes driven by glacier ice loss and increased precipitation will alter river water quality and chemical weathering regimes such that silicate weathering may become a more important source of solutes and sulfide oxidation may decrease. This contribution provides a platform to build from for future investigations into changes to stream water chemistry in the region and other high latitude watersheds.
  • Hydroclimate Drives Seasonal Riverine Export Across a Gradient of Glacierized High-Latitude Coastal Catchments

    Jenckes, Jordan (2023-01)
    Glacierized coastal catchments of the Gulf of Alaska are undergoing rapid hydrologic fluctuations in response to climate change. These catchments deliver dissolved and suspended inorganic and organic matter to nearshore marine environments, however, these glacierized coastal catchments are relatively understudied and little is known about total solute fluxes to the ocean. We present hydrologic, physical, and geochemical data collected during April-October 2019-2021 from 10 streams along gradients of glacial fed to non-glacial (i.e., precipitation) fed, in one Southcentral and one Southeast Alaska region. Hydrologic data reveal that glaciers have a dominating influence on seasonal runoff patterns. The ẟ18O signature and specific conductance show distinctive seasonal variations in stream water sources between the two study regions apparently due to the large amounts of rain in Southeast Alaska. Total dissolved solids concentrations and yields were elevated in the Southcentral region, due to lithologic influence on dissolved loads. Hydroclimate is the primary driver of the timing of dissolved and suspended yields in both regions of the Gulf of Alaska. We show the yields of dissolved organic carbon is higher and that the δ13CPOC is enriched in the Southeast streams illustrating contrasts in organic carbon export across the Gulf of Alaska. Furthermore, we illustrate how future yields of solutes and sediments to the Gulf of Alaska may change as watersheds evolve from glacial influenced to precipitation dominated. This integrated analysis provides insights into how watershed characteristics beyond glacier coverage control the properties of freshwater inputs to the Gulf of Alaska and the importance of expanding study regions to multiple hydroclimate regimes.
  • Lithium Storage and Release from Lacustrine Sediments: Implications for Lithium Enrichment and Sustainability in Continental Brines

    Coffey, Daniel; Munk, Lee Ann; Ibarra, Daniel; Butler, Kristina; Boutt, David; Jenckes, Jordan (2021)
    Despite current and projected future reliance on lithium as a resource, deficiencies remain in genesis models of closed-basin Li brines. Subsurface geochemical interactions between water and bulk solid phases from lacustrine sediments, are shown here to be the most important process for brine genesis and sustainability of the Clayton Valley, NV brine deposit. A new subsurface basin model was developed and used to select Li-bearing solids to test the release mechanisms for Li. Ash (20-350 ppm Li) and bulk sediments (1000-1700 ppm Li) samples across depths in the basin represent the majority of the subsurface Li-bearing materials. Temperature dependent (25-95 oC) batch reaction experiments using low-salinity groundwater from the basin indicate a positive relationship between the amount of Li released and temperature. Four-step sequential extractions on a subset of bulk sediments indicate most Li is released from water and weak acid-soluble portions with approximately 30% of the total Li contained in the sediments released overall. We conceptualize that lithium is released from these samples via three mechanisms: 1) release of adsorbed Li; 2) cation exchange of Li and Mg and; 3) possible minor release from silicate structure at elevated temperatures. Based on these results and the abundance of Li-bearing sediments in the subsurface we estimate the mean Li mass in the basin materials to be between 24.4 to 58.0 Mt. This Li provides a continuous supply from water-rock interactions. This is now the largest known accumulation of Li in a basin-fill continental setting on a global scale.
  • Concentration-Discharge Patterns Across the Gulf of Alaska Reveal Geomorphological and Glacierization Controls on Stream Water Solute Generation and Export

    Jenckes, Jordan; Ibarra, Daniel; Munk, Lee (2021-10-19)
    High latitude glacierized coastal catchments of the Gulf of Alaska (GoA) are undergoing rapid hydrologic changes in response to climate change and glacial recession. These catchments deliver important nutrients in the form of both inorganic and organic matter to the nearshore marine environment, yet are relatively understudied with respect to characterization of the sediment and solute generation processes and total yields. Using multiple linear regression informed by Bayesian Information Criterion analysis we empirically demonstrate how watershed characteristics affect suspended sediment and solute generation as represented by concentration-discharge relationships. We find that watershed mean slope and relief control solute generation and that solute yields are influenced most by glacier coverage. We contribute a new flux and concentration-discharge based conceptualization for understanding solute cycles across a hydroclimatic gradient of GoA watersheds that can be used to better understand future watershed responses to rapid hydrologic change.
  • Impact of Daily Arctic Sea Ice Variability in CAM3.0 during Fall and Winter

    Dammann, Dyre O.; Bhatt, Uma S.; Langen, Peter L.; Krieger, Jeremy R.; Zhang, Xiangdong (2013-03-15)
    Climate projections suggest that an ice-free summer Arctic Ocean is possible within several decades and with this comes the prospect of increased ship traffic and safety concerns. The daily sea ice concentration tendency in five Coupled Model Intercomparison Project phase 5 (CMIP5) simulations is compared with observations to reveal that many models underestimate this quantity that describes high-frequency ice movements, particularly in the marginal ice zone. To investigate whether high-frequency ice variability impacts the atmosphere, the Community Atmosphere Model, version 3.0 (CAM3.0), is forced by sea ice with and without daily fluctuations. Two 100-member ensemble experiments with daily varying (DAILY) and smoothly varying (SMTH) sea ice are conducted, along with a climatological control, for an anoma- lously low ice period (August 2006–November 2007). Results are presented for three periods: September 2006, October 2006, and December–February (DJF) 2006/07. The atmospheric response differs between DAILY and SMTH. In September, sea ice differences lead to an anomalous high and weaker storm activity over northern Europe. During October, the ice expands equatorward faster in DAILY than SMTH in the Siberian seas and leads to a local response of near-surface cooling. In DJF, there is a 1.5-hPa positive sea level pressure anomaly over North America, leading to anomalous northerly flow and anomalously cool continental U.S. temperatures. While the atmospheric responses are modest, the differences arising from high temporal frequency ice variability cannot be ignored. Increasing the accuracy of coupled model sea ice variations on short time scales is needed to improve short-term coupled model forecasts.
  • Spring Ice Trails 2013 - Barrow, Alaska

    Dammann, Dyre O.; Druckenmiller, Matt; Donovan, Michael; George, Craig (2013-06-17)
    Unusual sea ice conditions for the hunters of Barrow Alaska Following a record Arctic summer sea ice minimum in September 2012, this winter had an unusually low sea ice maximum extent. Although this winter maximum was only the fifth lowest on satellite records, this year’s winter sea ice proved to be different and challenging for the hunters of northern Alaska. The unusual season started with persistent storms from the west keeping temperatures high and prevented ice formation until early November. The shorefast ice following remained unusually smooth and undeformed. With very few ridges reaching the sea floor the stability of the shorefast ice was lower than usual and resulted in multiple break out events during spring. The unstable ice in combination with few open leads has resulted in a so far unsuccessful hunting season. Also notable this year is what appears to be a complete lack of multiyear ice in the region. The local population refers to this ice as piqaluyak, which is used for drinking water during long periods on the ice. Although not critical as a water source, the multiyear ice may play a significant role in creating stable safe ice for hunting. Whether this year will be remembered as an anomaly or as the new normal remains an open question.