Stream water and soil water chemistry after the Table Mountain wildfire, Washington, USA

Analyses of major and trace elements, major ions, and nutrient concentrations were made to investigate how stream water and soil water chemistry changed over 16 months following the Table Mountain wildfire. Sites with different burn severity were also compared. The fire occurred in 2012 in Kittitas County, north of Ellensburg, Washington. Samples were collected at severely burned, moderately burned, and unburned field sites from within and adjacent to the wildfire perimeter. Total nitrogen concentrations increased in the second year after the fire in both the severely and moderately burned sites. In contrast, total phosphorus was variable at all three sites and did not increase significantly after the fire. Major elements, trace elements, and major ion groups do not show a gradation from severely burned to moderately burned to unburned sites. However, both burned sites had soil waters with lower Ca/Mg ratios in the first year after the fire

Seasonal Dispersal of Fjord Meltwaters as an Important Source of Iron and Manganese to Coastal Antarctic Phytoplankton

Glacial meltwater from the western Antarctic Ice Sheet is hypothesized to be an important source of cryospheric iron, fertilizing the Southern Ocean, yet its trace-metal composition and factors that control its dispersal remain poorly constrained. Here we characterize meltwater iron sources in a heavily glaciated western Antarctic Peninsula (WAP) fjord. Using dissolved and particulate ratios of manganese to iron in meltwaters, porewaters, and seawater, we show that surface glacial melt and subglacial plumes contribute to the seasonal cycle of iron and manganese within a fjord still relatively unaffected by climate-change-induced glacial retreat. Organic ligands derived from the phytoplankton bloom and the glaciers bind dissolved iron and facilitate the solubilization of particulate iron downstream. Using a numerical model, we show that buoyant plumes generated by outflow from the subglacial hydrologic system, enriched in labile particulate trace metals derived from a chemically modified crustal source, can supply iron to the fjord euphotic zone through vertical mixing. We also show that prolonged katabatic wind events enhance export of meltwater out of the fjord. Thus, we identify an important atmosphere–ice–ocean coupling intimately tied to coastal iron biogeochemistry and primary productivity along the WAP

A "shallow bathtub ring" of local sedimentary iron input maintains the Palmer Deep biological hotspot on the West Antarctic Peninsula shelf

Palmer Deep (PD) is one of several regional hotspots of biological productivity along the inner shelf of the West Antarctic Peninsula. The proximity of hotspots to shelf-crossing deep troughs has led to the ‘canyon hypothesis’, which proposes that circumpolar deep water flowing shoreward along the canyons is upwelled on the inner shelf, carrying nutrients including iron (Fe) to surface waters, maintaining phytoplankton blooms. We present here full-depth profiles of dissolved and particulate Fe and manganese (Mn) from eight stations around PD, sampled in January and early February of 2015 and 2016, allowing the first detailed evaluation of Fe sources to the area's euphotic zone. We show that upwelling of deep water does not control Fe flux to the surface; instead, shallow sediment-sourced Fe inputs are transported horizontally from surrounding coastlines, creating strong vertical gradients of dissolved Fe within the upper 100 m that supply this limiting nutrient to the local ecosystem. The supply of bioavailable Fe is, therefore, not significantly related to the canyon transport of deep water. Near shore time-series samples reveal that local glacial meltwater appears to be an important Mn source but, surprisingly, is not a large direct Fe input to this biological hotspot

Sherrell Table S1-Dataset+legend from A ‘shallow bathtub ring’ of local sedimentary iron input maintains the Palmer Deep biological hotspot on the West Antarctic Peninsula shelf

Fe and Mn data for 8 stations in the Palmer Deep region, west Antarctic Peninsul