Reply on RC1

Matthias Fuchs

doi:10.5194/essd-2021-256-ac1

Abstract

Arctic river deltas and deltaic near-shore zones represent important land-ocean transition zones influencing sediment dynamics and nutrient fluxes from permafrost-affected terrestrial ecosystems into the coastal Arctic Ocean. To accurately model fluvial carbon and freshwater export from rapidly changing river catchments, as well assessing impacts of future change on the Arctic shelf and coastal ecosystems, we need to understand the sea floor characteristics and topographic variety of the coastal zones. To date, digital bathymetrical data from the poorly accessible, shallow and large areas of the eastern Siberian Arctic shelves are sparse. We have digitized bathymetrical information for nearly 75,000 locations from large-scale current and historical nautical maps of the Lena Delta and the Kolyma Gulf Region in Northeast Siberia. We present the first detailed and seamless digital models of coastal zone bathymetry for both delta/gulf regions. We validated the resulting bathymetry layers using a combination of our own water depth measurements and a collection of available depth measurements, which showed a strong correlation (r > 0.9). Our bathymetrical models will serve as an input for a high-resolution coupled hydrodynamic-ecosystem model to better quantify fluvial and coastal carbon fluxes to the Arctic Ocean but may be useful for a range of other studies related to Arctic delta and near-shore dynamics such as modelling of submarine permafrost, near-shore sea ice, or shelf sediment transport. The new digital high-resolution bathymetry products are available on the PANGAEA data set repository (Fuchs et al. 2021a, b). Likewise the depth validation data is available on PANGAEA as well (Fuchs et al., 2021c).

Highlights

The bathymetry of the Arctic Ocean at the mouths of major rivers is at the locus of interactions between land-to-ocean sediment fluxes, fluvial discharge, alongshore currents, and sea ice dynamics
Arctic river discharge is increasing (Peterson et al, 2002; McClelland et al, 2006; Haine et al 2015; Holmes et al, 2015; Brown et al, 2019), resulting in altered sediment, nutrient and organic carbon loads exported from rapidly changing river catchments into near-shore regions (e.g. Rachold et al, 2000; Gordeev, 2006; Tank et al, 2016; Wild et al, 2019) with unclear effects on the Arctic shelf and ocean ecosystems (Mann et al, in review; Polimene et al, in review)
We use water depth information from our own field-measured conductivity temperature and depth (CTD) observations as well as compiled water depth measurements synthesized from the PANGAEA data archive for both regions as a cross-validation data set for our digital bathymetry

Summary

Introduction

The bathymetry of the Arctic Ocean at the mouths of major rivers is at the locus of interactions between land-to-ocean sediment fluxes, fluvial discharge, alongshore currents, and sea ice dynamics. It exerts control on these processes and is shaped by them. Better baseline data are needed for Arctic deltas and their often very shallow subaquatic near-shore zones to quantify and model the effects of climate change induced disturbances upon these sensitive environments

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