Impacts of a recent storm surge on an Arctic delta ecosystem examined in the context of the last millennium

Abstract

One of the most ominous predictions related to recent climatic warming is that low-lying coastal environments will be inundated by higher sea levels. The threat is especially acute in polar regions because reductions in extent and duration of sea ice cover increase the risk of storm surge occurrence. The Mackenzie Delta of northwest Canada is an ecologically significant ecosystem adapted to freshwater flooding during spring breakup. Marine storm surges during the open-water season, which move saltwater into the delta, can have major impacts on terrestrial and aquatic systems. We examined growth rings of alder shrubs (Alnus viridis subsp. fruticosa) and diatoms preserved in dated lake sediment cores to show that a recent marine storm surge in 1999 caused widespread ecological changes across a broad extent of the outer Mackenzie Delta. For example, diatom assemblages record a striking shift from freshwater to brackish species following the inundation event.What is of particular significance is that the magnitude of this recent ecological impact is unmatched over the >1,000-year history of this lake ecosystem. We infer that no biological recovery has occurred in this lake, while large areas of terrestrial vegetation remain dramatically altered over a decade later, suggesting that these systems may be on a new ecological trajectory. As climate continues to warm and sea ice declines, similar changes will likely be repeated in other coastal areas of the circumpolar Arctic. Given the magnitude of ecological changes recorded in this study, such impacts may prove to be long lasting or possibly irreversible.paleoecology | paleolimnology | dendrochronology | limnology | salinization

Archaeological Site Vulnerability Modelling: The Influence of High Impact Storm Events on Models of Shoreline Erosion in the Western Canadian Arctic

“…As a result, archaeological sites located there are particularly vulnerable to climate related impacts such as permafrost depletion (Smith et al 2009), backshore thaw slump activation (Lantz, Kokelj 2008), increased severity and frequency of wind events and related storm surges (Pisaric et al 2011, Small et al 2011, and shoreline erosion (Solomon 2005). The region is notorious for its powerful northwesterly wind events, which typically increase in strength and frequency in the late autumn prior to freeze-up (Manson, Solomon 2007, Solomon 2005.…”

Selected topics in arctic atmosphere and climate

“…Moving to the north-northeast, it crossed the Rocky Mountains and reintensified over coastal waters of the southern Beaufort Sea, between the coast and pack ice, creating a storm surge and coastal flooding with extensive ecological damage, unmatched in the past 1,000 years (Pisaric et al 2011). It then moved northeastward, dissipating over the Canadian Archipelago by 26 September.…”

“…Southeasterly winds give negative surge, or set-down, whereas northwesterly winds give positive surge, or set-up. During the 1999 storm, during the negative surge (set-down), relatively fresh water left the nearshore areas; as the storm passed northwesterly, winds created a positive surge with higher salinity, flooding coastal areas, and killing vegetation as far as 30 km inland (Pisaric et al 2011;Melling et al 2011, this issue; see also Supplementary File #2).…”

Detecting Landscape Changes in High Latitude Environments Using Landsat Trend Analysis: 2. Classification

“…A large area of regeneration also appears at the northern tip of the Mackenzie Delta region that was impacted by a storm surge in 1999. According to [27], 90% of alder shrubs sampled died within five years following the event and soils contained high levels of chloride a decade later, inhibiting vegetation reestablishment. The process labelled "regeneration" largely refers to vegetation removal from fire and assumes subsequent regeneration, though regeneration rates can vary according to fire intensity and location [28].…”