Variability of Sediment Accumulation Rates in an Antarctic Fjord

Abstract

Fjords on the West Antarctic Peninsula (WAP) serve as sediment traps, preserving histories of glacial sediment supply. Regional warming trends are expected to change sediment supplies, altering water quality, depositional history, and ecosystem drivers. Our ability to assess magnitudes of these changes is limited by sparse data on modern sediment accumulation. Twelve new cores and four existing cores from Andvord Bay were used to characterize variability in sediment accumulation rates. These range from 1.5 to 7.9 mm/year (0.12 to 0.56 g·cm−2·year−1). Spatial differences and a weak down‐fjord gradient in rates suggest diverse sediment sources, including from outside the fjord. This data set provides a comprehensive assessment of sedimentation during the past century, indicating little change in rates due to recent WAP warming, and sets a benchmark for assessing climate‐related changes in sediment delivery and ecosystem drivers (e.g., burial disturbance) in the fjord over coming decades.

Seasonal dispersal of fjord meltwaters as an important source of iron to coastal Antarctic phytoplankton

“…Profiles of beam attenuation coefficient show highest concentration of particles in the inner basins compared to other station locations (see Figure 4 in Pan et al, 2019). There is little evidence for mechanical resuspension through gravity flows (i.e., turbidites) along the steep basin walls, yet such processes could be responsible for the near-bottom elevation in water column particles (Eidam et al, 2019). The presence of elevated particles in the inner basins is accompanied by the greatest concentrations of dissolved and labile particulate Fe and Mn (Fig.…”

“…Analyses of Andvord Bay sediments reveal they are compositionally distinct from temperate fjords consisting of poorly sorted fine silt and clay, many dropstones, suspension deposits and ice-rafted debris (Eidam et al, 2019). Sediment accumulation rates are spatially variable, but a weak along-fjord gradient is present.…”

“…A greater amount of sediment is expected to be released into the fjord, reducing light quality for primary producers, and as part of a natural tidewater glacier cycle (Brinkerhoff, Truffer and Aschwanden, 2017). This climatic trend is not yet realized within Andvord Bay (Eidam et al, 2019), but is expected to decrease Fe export through increased scavenging and sedimentation, further resembling high-Arctic and temperate fjords (Hopwood et al 2016). Therefore, a key question outside the scope of this research is how Fe-binding ligand complements will change in the future.…”

“…We present trace metal results from two expeditions (December 2015 and April 2016) to Andvord Bay, a cold glacio-marine fjord located mid-latitude along the WAP. This study is part of the FjordEco project which assessed the ecosystem function and seasonality of Andvord Bay (Pan et al 2019;Pan et al 2020;Ziegler et al 2020;Eidam et al 2019;Lundesgaard et al 2020Lundesgaard et al , 2019Hahn-Woernle et al 2020). The WAP is host to the most extensive collection of glaciomarine fjords on the at -20°C until complete digestion by HNO3/HF mixture.…”

Morainal Bank Evolution and Impact on Terminus Dynamics During a Tidewater Glacier Stillstand

“…The decay of accumulation rate down‐fjord is consistent with progressive settling of plume sediments and limited runout distances of gravity flows seen in other systems (e.g., Boulton, 1990; Curran et al, 2004; Meslard et al, 2018; Powell, 1990; Syvitski, 1989). Relative to fjords outside Alaska (e.g., Antarctica, Boldt et al, 2013; Canada, Smith & Walton, 1980; Eidam et al, 2019; Patagonia, Boldt et al, 2013; Svalbard, Elverhøi et al, 1983), accumulation rates in LeConte Bay tend to be 1–2 orders of magnitude greater.…”