Concentration‐Discharge Patterns Across the Gulf of Alaska Reveal Geomorphological and Glacierization Controls on Stream Water Solute Generation and Export

Abstract

High-latitude regions are warming at rates of two to three times the global average (IPCC, 2007). Precipitation regime changes associated with the increasing temperatures will result in increased precipitation, primarily in the form of autumn and winter rain (Beamer et al., 2017). Associated with these changes, global glacier volume will decline 29-41% by 2100 compared to 2006 accompanied by a projected 20% decline in global glacier runoff (Radić et al., 2014). Ice fields and glaciers cover 18% of the 420,230 km 2 Gulf of Alaska (GoA) region and supply 47% of the freshwater water runoff (Neal et al., 2010). Looking to the future it is predicted that Alaska will experience a 30% decline in runoff by the end of the 21st century (Bliss et al., 2014) accompanied by a forecasted decrease of glacier volume between 32 ± 11 and 58 ± 14% for RCP2.6 and RCP8.5, respectively (Huss & Hock, 2015). As such, the climate change predicted for the 21st century will significantly alter the amount of freshwater discharging to the GoA along with changes in precipitation regimes. Currently, glacial fed streams have increased discharge compared to nonglacial precipitation fed streams. This paradigm will shift as coastal glacier coverage declines into the 21st century. Today, glaciers act as a control on seasonal runoff variation within a catchment. Stream discharge within a glacierized basin varies little year to year and peak runoff is generally predictable. Precipitation fed streams, conversely, have higher interannual variations in discharge due to their susceptibility to interannual climate variability. For example, Fountain and Tangborn (1985) suggest that basins with glacial coverage around 36% have the lowest year-to-year variation in discharge. Streams with less than 10% glacier cover, however, show large year to year variability in stream flow when compared to streams within watersheds with greater percentages of glacier coverage (Fountain & Tangborn, 1985).

Maritime glacier retreat and terminus area change in Kenai Fjords National Park, Alaska, between 1984 and 2021

“…Changes to tidewater glaciers will influence nearshore oceanography and marine ecosystems (Lydersen and others, 2014; O'Neel and others, 2015; Arimitsu and others, 2016). The local fjord marine environments are changing as changes in glacier melt result in changes to the volume of fresh water input (Neal and others, 2010), which affects local physical oceanographic properties such as temperature, salinity and turbidity (Etherington and others, 2007; Hood and Berner, 2009; Hood and others, 2009; Arimitsu and others, 2012, 2016; Jenckes and others, 2022), nutrients (Hood and Scott, 2008; Whitney and others, 2018) and currents (Royer, 1981). Meltwater and sediment discharge from tidewater glaciers drive fjord temperature and turbidity (Arimitsu and others, 2016).…”

Marine and Not Terrestrial Resources Support Nearshore Food Webs Across a Gradient of Glacial Watersheds in the Northern Gulf of Alaska

“…In contrast, the δ 13 C values of autotrophs (e.g., phytoplankton, macroalgae) are determined by uptake fractionation during photosynthesis (Keller & Morel, 1999), which is in uenced by cell physiology (Popp et al, 1998), ambient environmental conditions (Burkhardt et al, 1999), and the availability of dissolved inorganic carbon (DIC) (Sharkey & Berry, 1985;Lammers et al, 2017). The mobilization of geogenic DIC is especially high in highlatitude, watersheds with glacial coverage due to physical weathering associated with glacial movement (Tranter & Wadham, 2013), and the DIC yield is often greater in watersheds of higher glacial coverage relative to those of lower or no coverage (Jenckes et al, 2022). This pattern is consistent with the positive relationship between the ux of DIC and glacial coverage of watersheds in this study (Appendix I, Table A1).…”

“…In high-latitude regions, estuarine systems experience added complexity from the in ux of glacial meltwater where cold, turbid water from glaciers can modify downstream conditions in local estuaries. The relative proportion of glacial input to a watercourse will ultimately affect estuarine temperature, light attenuation (Ren et al, 2019), nutrient concentrations (Hood & Scott, 2008Jenckes et al, 2022), and discharge volume (Sergeant et al, 2020). The in uence of glaciers on OM terr delivery was recognized in southeast Alaskan estuarine food webs, where select invertebrates (e.g., Mytilus trossulus) displayed greater assimilation of OM terr at locations of greater glacial in uence (Arimitsu et al, 2018).…”

Contribution of fresh submarine groundwater discharge to the Gulf of Alaska

“…Additionally, forecast modeling predicts that the current rise in temperatures will result in increasing precipitation, most notably in the form of fall and winter rains (Beamer et al, 2017). This immense hydrologic discharge transports with it an abundance of terrigenous materials, including sediments, solutes and nutrients, that mediate marine ecosystems (Hood et al, 2009;Edwards et al, 2021;Jenckes et al, 2021) and retain a dominant influence on local and regional oceanographic processes (Weingartner et al, 2005).…”