Presentation Information
[ACC42-05]Holocene evolution of permafrost-dominated nearshore environment and carbon source variability in Tuktoyaktuk Harbor, Canadian Beaufort Sea
*Blanda Anita Matzenbacher1,2, Tommaso Tesi3, Petra Zahajska4, Bennet Juhls5, Michael Fritz5, Lisa Bröder6, Malin Kylander1,2, Peter D. Heintzman1,2, Julie Lattaud1,2, Katharina Schwarzkopf1,2, Inda Brinkmann1,2, Pier Paul Overduin5, Dustin Whalen7, Matthew O'Regan1,2 (1.Stockholm Univ., 2.Bolin Center, 3.CNR-ISP, 4.Univ. of Bern, 5.AWI, 6.ETH Zurich, 7.NRCan)
Keywords:
Mackenzie River basin environmental change,Canadian Beaufort Sea coastal erosion,Holocene marine transgression sediment record,Tuktoyaktuk Harbor NWT Canada,Holocene permafrost carbon remobilization,permafrost landscape evolution
Future sea-level rise and its impact on coastal erosion are a risk for Arctic communities. The Canadian Beaufort Sea is characterized by predominantly permafrost coastlines that are particularly vulnerable to coastal erosion due to high amounts of unconsolidated sediments. In addition, the Mackenzie River transports suspended sediments from its extensive permafrost-rich watershed across northwestern Canada and discharges large amounts of remobilized organic matter in nearshore environments. Deposition of organic-rich material impacts the biogeochemistry of coastal waters with direct implications for local ecosystems. The rate at which marginal coasts erode and sediment accumulates in the nearshore environment is expected to increase with rising sea level and enhanced fluvial sediment transport under a warming climate.
To understand how these coastal systems may develop in the future, and the potential consequences for local communities, it is essential to investigate their past evolution. This marginal coastal setting provides a unique archive to investigate the interplay between environmental change, landscape evolution and the response of marine ecosystems. In this study, a ~9 m long sediment core from Tuktoyaktuk Harbor was investigated to resolve past variability in sediment and terrestrial carbon delivery to the nearshore environment. The sediment core is constrained by a well-established age model spanning the last 10,000 years and provides a high-resolution archive of environmental change.
Our results show that the site initially hosted a freshwater bog in the Early Holocene before transitioning into a thermokarst lake during the mid-Holocene. Marine inundation associated with sea-level rise occurred at 3340 ± 328 cal yr BP, initially transforming the system into a methane-producing lagoon under strongly anoxic conditions. Continued marine transgression reduced anoxia over time leading to the establishment of the brackish back-barrier estuarine lagoon that characterizes Tuktoyaktuk Harbor today. Lignin biomarkers support these findings indicating predominantly autochthonous organic matter during the Early to mid-Holocene, and an increase in allochthonous gymnosperm input in the Late Holocene most likely delivered by the Mackenzie River.
Over the last millennium deposits exhibit a notable increase in the amount of petrogenic carbon, indicating enhanced erosion of ancient carbon stocks within the Mackenzie River watershed. The biotic response of the marine and terrestrial ecosystems to environmental and landscape evolution is being investigated in a parallel study employing shotgun sequencing of sedimentary ancient DNA.
To understand how these coastal systems may develop in the future, and the potential consequences for local communities, it is essential to investigate their past evolution. This marginal coastal setting provides a unique archive to investigate the interplay between environmental change, landscape evolution and the response of marine ecosystems. In this study, a ~9 m long sediment core from Tuktoyaktuk Harbor was investigated to resolve past variability in sediment and terrestrial carbon delivery to the nearshore environment. The sediment core is constrained by a well-established age model spanning the last 10,000 years and provides a high-resolution archive of environmental change.
Our results show that the site initially hosted a freshwater bog in the Early Holocene before transitioning into a thermokarst lake during the mid-Holocene. Marine inundation associated with sea-level rise occurred at 3340 ± 328 cal yr BP, initially transforming the system into a methane-producing lagoon under strongly anoxic conditions. Continued marine transgression reduced anoxia over time leading to the establishment of the brackish back-barrier estuarine lagoon that characterizes Tuktoyaktuk Harbor today. Lignin biomarkers support these findings indicating predominantly autochthonous organic matter during the Early to mid-Holocene, and an increase in allochthonous gymnosperm input in the Late Holocene most likely delivered by the Mackenzie River.
Over the last millennium deposits exhibit a notable increase in the amount of petrogenic carbon, indicating enhanced erosion of ancient carbon stocks within the Mackenzie River watershed. The biotic response of the marine and terrestrial ecosystems to environmental and landscape evolution is being investigated in a parallel study employing shotgun sequencing of sedimentary ancient DNA.