Jennifer Martine Jackson

Down-fjord winds have been implicated in upwelling and exchange of water in fjords. In one temperate fjord, strong winds oxygenated and cooled water deeper than 100 m. Deep temperature minima accompanied by oxygen maxima are a common feature in fjords, yet do not have a ready prediction. Here, it is shown that the dominant process driving the upwelling is wind-driven transport divergence at the head of the fjord, as opposed to local convection due to cooling or mechanical mixing. Previous work has focused on two-layer approximations, but those fail to differentiate the depth of upwelling if the bottom layer is continuously stratified. Simulations with a constant stratification show that the depth that the densest water comes from is proportional to , where L is the length of the fjord or the horizontal scale of the wind, is the wind stress, and N² is the buoyancy profile. The time scale of the upwelling is similarly scaled as . These scalings apply over a wide range of forcings and geometry, so long as the depth scale does not approach the depth of the fjord. A simple procedure can be used to get a similar scaling if N(z) is not constant. If the wind is allowed to relax, the simulations come back to rest after a vigorous seiche, subducting the upwelled water. Despite strong turbulence, the net exchange with water outside the fjord is found to be small, and oxygen concentrations are mostly modified by air–sea gas exchange rather than diapycnal mixing. Significance Statement: Upwelling in fjords due to down-fjord winds has the potential to ventilate deep water and to drive exchange with water outside the fjord. Here, we offer a simple method to predict the depth and time scale of the upwelling based on the wind strength, the initial stratification, and the length of the fjord. Vertical mixing has only a minor impact on the vertical distribution of properties in the fjord due to the wind events, and much of the transport into the fjord is reversible in the absence of other mixing sources.

Glacial lake outburst floods can transport large volumes of sediment. Where these floods reach the coastline, much of the particulate matter is delivered directly to the marine environment. It has been suggested that offshore deposits, specifically in fjord settings, may provide a faithful record of past outburst flood events. However, a lack of observations means that the mechanics and the timing of sediment transport offshore following a glacial lake outburst event remain poorly constrained. Here, we document the changes in sea surface sediment dynamics following the 28 November 2020 Elliot Lake outburst flood in British Columbia, which transported ∼4.3 × 10⁶ m³ of sediment into an adjacent fjord (Bute Inlet) as a deep nepheloid layer directly following the event. However, analysis of sea surface turbidity using in situ measurements and satellite‐derived estimates reveals that changes in fjord‐head surface turbidity in the months following the major flood were surprisingly small. The highest measured sea surface turbidity instead occurred 5 months after the initial outburst flood. This delayed increase in seaward sediment flux coincided with the onset of the spring freshet, when the discharge of the rivers feeding Bute Inlet increases each year. We suggest that large quantities of sediment were temporarily stored within the river catchment and were only remobilized when river discharge exceeded a threshold level following seasonal snowmelt. Our results reveal a temporal disconnect, where onshore to offshore transfer of sediment is stepped following a glacial lake outburst flood, which could complicate the sedimentology of subsequent deposits.

Disease outbreaks as a driver of wildlife mass mortality events have increased in magnitude and frequency since the 1940s. Remnant populations, composed of individuals that survived mass mortality events, could provide insight into disease dynamics and species recovery. The sea star wasting disease (SSWD) epidemic led to the rapid >90% decline of the sunflower star Pycnopodia helianthoides . We surveyed the biomass density of P. helianthoides on the central British Columbia coast before, during and after the arrival of SSWD by conducting expert diver surveys in shallow subtidal habitats from 2013 to 2023. We found a rapid decline in biomass density following the onset of SSWD in 2015. Despite consistent recruitment post-outbreak to sites associated with outer islands, we found repeated loss of large adult individuals over multiple years. Within nearby fjord habitats, we found remnant populations composed of large adult P. helianthoides . The interaction of temperature and salinity with the biomass density of P. helianthoides varied by location, with high biomass density associated with higher temperatures in the outer islands and with lower temperatures and higher salinity in the fjords. These patterns suggest that fjords provide refuge from consequences of SSWD and protecting these populations could be imperative for the species.

G̱andaawuu.ngaay Xyangs (Juan Perez Sound) is a fjord‐like area and ecological hotpot on the east coast of Haida Gwaii, British Columbia, within Gwaii Haanas National Park Reserve, National Marine Conservation Area Reserve, and Haida Heritage Site. A collaboration among the Council of the Haida Nation, Parks Canada, and Fisheries and Oceans Canada has been ongoing since 2017 to advance understanding of the oceanography and marine ecology within and around Gwaii Haanas. Oceanographic data collected year‐round by subsurface moorings and annually on research cruises revealed winter dissolved oxygen concentrations (DO) greater than 5 mLL⁻¹ (217 μmol kg⁻¹) as deep as 350 m in G̱andaawuu.ngaay Xyangs and no evidence of hypoxia throughout the water column. This observation differs from other British Columbia fjords, where maximum deep DO is generally observed in summer and values can be hypoxic or anoxic in winter. To explain this high DO, potential energy in the water column was calculated and compared with wind energy. Strong winds and weak stratification facilitated mixing of the water column each winter enabling ventilation. Oxygen loss from the winter high was caused by both frequent episodes of advection of dense, DO‐poor water from shelf waters into G̱andaawuu.ngaay Xyangs, and by remineralization. In comparison, in Rivers Inlet, weak winds and strong stratification prevented full water column mixing and ventilation. Although climate‐driven changes such as intensified upwelling, enhanced stratification, and region‐wide deoxygenation could cause future hypoxia, protecting the integrated land‐ocean ecosystem in G̱andaawuu.ngaay Xyangs is more important than ever before.

Glacial lake outburst floods can transport large volumes of sediment. Where these floods reach the coastline, much of that particulate load is delivered directly to the marine environment. It has been suggested that offshore deposits, specifically in fjord settings, may provide a faithful record of the frequency and timing of past outburst flood events. However, a paucity of observations means that the mechanics and the timing of offshore transport of sediment following a glacial lake outburst event remain poorly constrained. Here, we document the changes in sea surface sediment dynamics following the 28th November 2020 Elliot Lake outburst flood in British Columbia, which transported ~4.3x106 m3 of sediment into an adjacent fjord (Bute Inlet) as a deep nepheloid layer directly following the event. However, analysis of sea surface turbidity using in situ measurements and satellite-derived estimates reveals that changes in fjord-head surface turbidity immediately following the major flood were surprisingly small. The highest measured sea surface turbidity instead occurred five months after the initial outburst flood. This delayed increase in seaward sediment flux was coincident with the onset of the spring freshet, when discharge of the rivers feeding Bute Inlet increase each year. We suggest that large quantities of sediment were temporarily stored within the river catchment, and only remobilised when river discharge exceeded a threshold level following seasonal snowmelt. Our results reveal a temporal disconnect, where onshore to offshore transfer of sediment is stepped following a glacial lake outburst flood, which could complicate the architecture of subsequent deposits.

As on land, oceans exhibit high temporal and spatial temperature variation. This “ocean weather” contributes to the physiological and ecological processes that ultimately determine the patterns of species distribution and abundance, yet is often unrecognized, especially in tropical oceans. Here, we tested the paradigm of temperature stability in shallow waters (<12.5 m) across different zones of latitude. We collated hundreds of in situ, high temporal-frequency ocean temperature time series globally to produce an intuitive measure of temperature variability, ranging in scale from quarter-diurnal to annual time spans. To estimate organismal sensitivity of ectotherms (i.e. microbes, algae, and animals whose body temperatures depend upon ocean temperature), we computed the corresponding range of biological rates (such as metabolic rate or photosynthesis) for each time span, assuming an exponential relationship. We found that subtropical regions had the broadest temperature ranges at time spans equal to or shorter than a month, while temperate and tropical systems both exhibited narrow (i.e. stable) short-term temperature range estimates. However, temperature-dependent biological rates in tropical regions displayed greater ranges than in temperate systems. Hence, our results suggest that tropical ectotherms may be relatively more sensitive to short-term thermal variability. We also highlight previously unexplained macroecological patterns that may be underpinned by short-term temperature variability.

Vertical migrations of zooplankters have been widely described, but their active movements through shallow, highly dynamic water columns within the inner shelf may be more complex and difficult to characterize. In this study, invertebrate larvae, currents, and hydrographic variables were sampled at different depths during and after the presence of fronts on three different cruises off the southern coast of South Africa. Internal wave dynamics were observed in the hydrographic data set but also through satellite imagery, although strong surface convergent currents were absent and thermal stratification was weak. During the first two cruises, fronts were more conspicuous and they preceded strong onshore currents at depth which developed with the rising tide. Vertical distributions of larvae changed accordingly, with higher abundances at these deep layers once the front disappeared. The third cruise was carried out during slack tides, the front was not conspicuous, deep strong onshore currents did not occur afterward and larval distributions did not change consistently through time. Overall, the vertical distributions of many larval taxa matched the vertical profiles of shoreward currents and multivariate analyses revealed that these flows structured the larval community, which was neither influenced by temperature nor chlorophyll. Thus, the ability to regulate active vertical positioning may enhance shoreward advection and determine nearshore larval distributions.

Arctic outflow winds bring cold air from the continent to the coastline through mountain passes. Using observational data and a 2‐D model, we show that a February 2019 outflow event caused the upper 100 m in Bute Inlet, British Columbia (within the traditional territory of the Homalco Nation) to cool up to 1.9°C and gain up to 4.1 mLL⁻¹ of oxygen. The cold, oxygenated water persisted for almost 1 year within the 1,023–1,023.5 kgm⁻³ isopycnal range (∼50–150 m). Atmospheric (from 1929 to 2022) and oceanographic (from 1951 to 2022) data showed a statistically significant relationship between continental air temperature at Tatlayoko Lake and temperature and oxygen in Bute Inlet. This local mechanism that counters some effects of climate change could create a biological refugium as surrounding waters warm and lose oxygen at a faster rate. The number of outflow events decreased from 1951 to 2018, and increased since.

Phytoplankton phenology studies require a dataset that is continuous in time and space since missing data have been shown to affect the accuracy of seasonality metrics. The interpolated GlobColour product provided by the Copernicus Marine Environment Monitoring Service (CMEMS) meets these requirements by being ‘gap filled’, thus yielding the highest spatial coverage. Despite being validated on a global scale, a regional comparison to in situ Chl-a concentrations should be conducted to enable product application in optically complex waters. This study aims to evaluate the performance of the GlobColour interpolated product in British Columbia coastal waters via a statistical match-up analysis and a qualitative analysis to determine whether the data reflect the region’s large-scale seasonal trends and latitudinal dynamics. Additionally, the statistical performance of the GlobColour interpolated product was compared to the original GlobColour and Ocean Colour Climate Change Initiative (OC-CCI) merged chlorophyll-a products based on in situ observations. The GlobColour interpolated product performed relatively well and was comparable to the best-performing product for each water type (RMSE = 0.28, r² = 0.77, MdAD = 1.5, BIAS = 0.90). The statistics for all the products degraded in Case 2 waters, thus highlighting the dilemma of applying algorithms designed for Case 1 waters in Case 2 waters. Our results indicate how the quality of products can vary in different environmental conditions.

We describe and model the evolution of a recent landslide, tsunami, outburst flood, and sediment plume in the southern Coast Mountains, British Columbia, Canada. On November 28, 2020, about 18 million m³ of rock descended 1,000 m from a steep valley wall and traveled across the toe of a glacier before entering a 0.6 km² glacier lake and producing >100‐m high run‐up. Water overtopped the lake outlet and scoured a 10‐km long channel before depositing debris on a 2‐km² fan below the lake outlet. Floodwater, organic debris, and fine sediment entered a fjord where it produced a 60+km long sediment plume and altered turbidity, water temperature, and water chemistry for weeks. The outburst flood destroyed forest and salmon spawning habitat. Physically based models of the landslide, tsunami, and flood provide real‐time simulations of the event and can improve understanding of similar hazard cascades and the risk they pose.