Changing Ocean Conditions Research Articles

From land to sea: provenance, composition, and preservation of organic matter in a marine sediment record from the North‐East Greenland shelf spanning the Younger Dryas–Holocene

The organic matter content of marine sediments is often used to infer past changes in ocean conditions. However, the organic carbon pool preserved in coastal sediments is a complex mixture derived from different sources and may not reflect in situ processes. In this study, we combine taxonomic identification of reworked palynomorphs with pyrolysis organic geochemistry and reflected‐light organic petrographic microscopy to investigate the provenance, composition and preservation of organic matter in a marine sediment core retrieved from the NE Greenland shelf. Our study reveals continuous yet variable input of land‐derived organic carbon to the marine environment throughout the late Younger Dryas–Holocene, with the highest input of inert carbon in the late Younger Dryas. Although the sediments contain some recent marine palynomorphs, there is no other evidence of fresh marine organic carbon. In contrast, our results indicate that these shelf sediments represent a significant sink of recycled organic carbon. The results of pyrolysis geochemistry revealed that ~90% of the total organic carbon in the sediments is inert. The organic petrography analyses revealed that >70–84% of the organic carbon in the sediment core is terrigenous. Reworked dinoflagellate cysts showed a continuous provenance of Cretaceous land‐derived material, most likely from the nearby Clavering Island. Our study points to the importance of constraining the organic matter origin, composition and preservation in marine sediments to achieve more accurate palaeoenvironmental reconstructions based on organic proxies.

Integrating fishers’ knowledge with oceanographic observations to understand changing ocean conditions in the Northeast United States

Recent warming in the Northeast United States continental shelf ecosystem has raised several concerns about the impacts on the ecosystem and commercial fisheries. In 2014, researchers from the Commercial Fisheries Research Foundation and Woods Hole Oceanographic Institution founded the Shelf Research Fleet to involve fishers in monitoring the rapidly changing ocean environment and encourage sharing of ecological knowledge. The Shelf Research Fleet is a transdisciplinary, cooperative program that trains commercial fishers to collect oceanographic information by deploying conductivity, temperature, and depth (CTD) instruments while commercially fishing. A total of 806 CTD profiles have been collected by the Shelf Research Fleet through December 2022. Participating vessels can view the conductivity and temperature water column profiles they collect in real-time. These profiles help inform their fishing practices and give insights when unexpected species appear in their gear or if their catch composition changes from previous years. The data collected by the Shelf Research Fleet are shared with and processed by researchers from numerous partnering institutions. The Shelf Research Fleet data have been used by researchers to better understand oceanographic phenomena including marine heatwaves, shelf-break exchange processes, warm core rings, and salinity maximum intrusions onto the continental shelf. The scope of the Shelf Research Fleet has grown over time to include efforts to more directly link oceanographic results with biological observations to better understand how changing ocean conditions are affecting commercially important species. This article describes the approach, successes, challenges, and future directions of the Shelf Research Fleet and aims to outline a framework for a cost-effective research program that engages fishers in the collection of oceanographic data, strengthening partnerships between fishing industry members and the scientific community.

Glacier Mass Loss Between 2010 and 2020 Dominated by Atmospheric Forcing

AbstractWe generate a high spatial and temporal record of ice loss across glaciers globally for the first time from CryoSat‐2 swath interferometric radar altimetry. We show that between 2010 and 2020, glaciers lost a total of 272 ± 11 Gt yr−1 of ice, equivalent to a loss of 2% of their total volume during the 10‐year study period. Using a simple parameterization, we demonstrate that during this period, surface mass balance anomaly dominated the mass budget, accounting for 89% ± 5% of the total ice loss. Ice discharge anomaly was responsible for 11% ± 1% of the total ice loss, and 28% ± 2% of the ice loss when excluding land‐terminating sectors. Strong discharge anomaly is found over areas of changing oceanic conditions such as in the Barents and Kara Seas or in Antarctica, and areas fringed by lakes and fjords in Patagonia.

Strong Ocean Melting Feedback During the Recent Retreat of Thwaites Glacier

AbstractAccelerating ice loss from Thwaites Glacier is contributing approximately 5% of global sea‐level rise, and could add tens of centimeters to sea level over the coming centuries. We use an ocean model to calculate sub‐ice melting for a succession of Digital Elevation Models of the main trunk of Thwaites Glacier from 2011 to 2022. The ice evolution during this period induces a strong geometrical feedback onto melting. Ice thinning and retreat provides a larger melting area, thicker and better‐connected sub‐ice water column, and steeper ice base. This leads to stronger sub‐ice ocean currents, increasing melting by over 30% without any change in forcing from wider ocean conditions. This geometrical feedback over just 12 years is comparable to melting changes arising from plausible century‐scale changes in ocean conditions and subglacial meltwater inflow. These findings imply that ocean‐driven ice loss from Thwaites Glacier may only be weakly influenced by anthropogenic emissions mitigation.

Genome-wide phylogeography reveals cryptic speciation in the circumglobal planktonic calcifier Limacina bulimoides.

Little is known about when and how planktonic species arise and persist in the open ocean without apparent dispersal barriers. Pteropods are planktonic snails with thin shells susceptible to dissolution that are used as bio-indicators of ocean acidification. However, distinct evolutionary units respond to acidification differently, and defining species boundaries is therefore crucial for predicting the impact of changing ocean conditions. In this global population genomic study of the shelled pteropod Limacina bulimoides, we combined genetic (759,000 single nucleotide polymorphisms) and morphometric data from 161 individuals, revealing three major genetic lineages (FST = 0.29-0.41): an "Atlantic lineage" sampled across the Atlantic, an "Indo-Pacific lineage" sampled in the North Pacific and Indian Ocean, and a "Pacific lineage" sampled in the North and South Pacific. A time-calibrated phylogeny suggests that the lineages diverged about 1 million years ago, with estimated effective population size remaining high (~10 million) throughout Pleistocene glacial cycles. We do not observe any signatures of recent hybridization, even in areas of sympatry in the North Pacific. While the lineages are reproductively isolated, they are morphologically cryptic, with overlapping shell shape and shell colour distributions. Despite showing that the circumglobal L. bulimoides consists of multiple species with smaller ranges than initially thought, we found that these pteropods still possess high levels of genetic variability. Our study adds to the growing evidence that speciation is often overlooked in the open ocean, and suggests the presence of distinct biological species within many other currently defined circumglobal planktonic species.

Ocean‐Forcing and Glacier‐Specific Factors Drive Differing Glacier Response Across the 69°N Boundary, East Greenland

AbstractThe Greenland ice sheet has become a significant contributor to global sea level rise over the last 40–50 years. Approximately half of Greenland's mass loss since 1992 was due to increased ice discharge from marine‐terminating outlet glaciers. Here, we present high temporal resolution (∼monthly) time series of ice frontal positions for 24 marine‐terminating outlet glaciers along Greenland's east coast between 2013 and 2020. The glaciers are located north and south of 69°N, which has previously been identified as a potential divide in glacier response to climate forcing. Frontal positions are compared to ice velocity, atmospheric and oceanic data, allowing investigation of change at both seasonal and interannual timescales. Our results reveal 19 of 24 study glaciers underwent net retreat. We find marked differences in interannual patterns of frontal position between glaciers located north and south of 69°N. South of 69°N, glaciers underwent multiyear retreat initiated in 2016, which we attribute to over‐winter calving, resulting from warmer ocean waters and repeated ice‐mélange break‐up. North of 69°N glaciers show either limited or gradual changes in frontal positions and retreat patterns are characterized by more year‐on‐year variability between glaciers. Although similar atmospheric conditions occur across both regions, glaciers north of 69°N experience minimal change in ocean conditions, and are strongly influenced by glacier‐specific factors. Our results show that 69°N continues to represent a boundary between different glacier responses and climate forcing, which is likely to persist under current conditions.

Larval rockfish growth and survival in response to anomalous ocean conditions

Understanding how future ocean conditions will affect populations of marine species is integral to predicting how climate change will impact both ecosystem function and fisheries management. Fish population dynamics are driven by variable survival of the early life stages, which are highly sensitive to environmental conditions. As global warming generates extreme ocean conditions (i.e., marine heatwaves) we can gain insight into how larval fish growth and mortality will change in warmer conditions. The California Current Large Marine Ecosystem experienced anomalous ocean warming from 2014 to 2016, creating novel conditions. We examined the otolith microstructure of juveniles of the economically and ecologically important black rockfish (Sebastes melanops) collected from 2013 to 2019 to quantify the implications of changing ocean conditions on early growth and survival. Our results demonstrated that fish growth and development were positively related to temperature, but survival to settlement was not directly related to ocean conditions. Instead, settlement had a dome-shaped relationship with growth, suggesting an optimal growth window. Our results demonstrated that the dramatic change in water temperature caused by such extreme warm water anomalies increased black rockfish growth in the larval stage; however, without sufficient prey or with high predator abundance these extreme conditions contributed to reduced survival.

Widespread southern elephant seal occupation of the Victoria land coast implies a warmer-than-present Ross Sea in the mid-to-late Holocene

Prediction of future ice-sheet behavior in Antarctica and its contribution to sea-level rise depends on accurate understanding of ice-sheet response to a warm climate. Examination of how the ice sheet reacted to past warm episodes affords a means of assessing its tolerances to climate change. The West Antarctic Ice Sheet (WAIS), in particular, is thought to be highly susceptible to variations in ocean temperature at its grounding lines. Yet, detailed records of past ocean temperatures close to the continent are rare. Here, we present a record of past relative ocean-temperature and sea-ice change derived from the presence and then eventual abandonment of southern elephant seal (Mirounga leonina) occupation sites along the Victoria Land Coast (VLC) of the western Ross Embayment. Our results suggest greatly reduced landfast and likely pack ice, as well as potentially the incursion of relatively warm modified Circum-Polar Deep Water from ∼7100 to 500 yr BP, with the greatest reduction in ice/warmest water temperatures at ∼5200 and ∼2300-1800 yr BP. These changes in ocean conditions would have had a strong influence on VLC marine-terminating glaciers through variations in buttressing sea ice and melt rates on the underside of floating ice. Independent data suggest that these glaciers had restricted extent in the mid-Holocene, consistent with our inference of warm ocean temperatures and low sea ice. The glaciers subsequently expanded within the last millennium, coincident with the disappearance of southern elephant seals from the coast and the inferred return to icy conditions. Our relative sea-ice and ocean-temperature reconstruction also is consistent with the hypothesized retreat of the WAIS inland of its present position in the mid to late Holocene, although the distance between our sites and the current WAIS grounding lines is large (600–1000 km), and thus any linkage is speculative at present. Finally, limited pre-Holocene southern elephant seal data support the existence of warm ocean temperatures immediately prior to and perhaps even during build-up to the Last Glacial Maximum (LGM) ice position. If this could be confirmed, it would suggest that factors other than ocean temperatures, such as lowered sea level, might have been critical in causing ice-sheet advance in the Ross Embayment at the LGM.

Climate-induced changes in ocean productivity and food-web functioning are projected to markedly affect European fisheries catch

In European waters, climate-induced changes in ocean conditions will alter marine ecosystems, leading to potential repercussions for the European fisheries and the status of exploited species. Here, we used a new version of the EcoTroph model, forced by a regional high-resolution coupled hydrodynamic-ecosystem model, to investigate the effects of climate change on biomass and catch in 15 areas (ICES divisions) of the European Atlantic shelf ecosystems. Based on the projected changes in temperature, zooplankton and benthic secondary producers, we modeled the changes in biomass and catch at each trophic level by the end of the 21st century. We projected that total biomass and catch for the whole Atlantic European seas would decrease by 11.5 and 10.0%, respectively, by 2090-2099 relative to 2013-2017 under a ‘no mitigation’ greenhouse gases emissions scenario (RCP8.5). The projected decrease in catch is 310000 or 240000 t by 2090-2099 under a high (RCP8.5) or a moderate (RCP4.5) emissions scenario, respectively. Some areas, such as the Celtic Sea, would be more affected than others, while the climate impact on the bentho-demersal biomass and catches would be more pronounced, especially toward the higher trophic levels. Our study suggests that climate change may strongly impact European fisheries, with ecological consequences and potential socio-economic repercussions. Future studies using alternative climate and ecosystem models would allow the exploration of uncertainties in projected biomass and catch. While fisheries management is required to adapt to these changes, the projected impacts on catch cannot be avoided without aggressive mitigation of greenhouse gas emissions.

Evidence of likely foraging by pygmy blue whales in the Timor Trough during the late austral winter and early austral spring

Understanding the behavioural context of wildlife movement patterns is imperative to the conservation of migratory species like cetaceans. The traditional model of baleen whale migration entails uninterrupted journeys performed throughout extended periods of fasting, during which individuals sustain the enormous costs of travelling from the poles to the tropics only from energy reserves acquired prior to departure. However, this ‘feast and famine’ paradigm is being challenged by increasing observations of supplemental feeding events along whale migratory routes. In this context, identifying the location of migratory stopovers is key to managing cetacean populations, particularly in data-poor ecosystems subject to changing ocean conditions. We report on likely foraging activity by migrant pygmy blue whales Balaenoptera musculus brevicauda in the Timor Trough (ca. 9.5° S, 126° E), a deep-water habitat south of the species’ presumed breeding grounds. Using photo-identification and generalised additive modelling, we analysed visual sightings collected aboard seismic vessels operating off Timor-Leste in 2007-2008 and demonstrate that (1) whales engage in surface behaviours suggestive of active feeding, (2) some individuals remain within the region for more than 1 d, and (3) whale presence is significantly associated with predictably high chlorophyll a concentrations. Despite previous efforts to examine pygmy blue whale movements at low latitudes using long-term satellite telemetry, knowledge of the species’ behavioural ecology in the tropics remains limited. Our results lend support to previously untested hypotheses about the possible use of the Timor Trough as a foraging site by eastern Indian Ocean pygmy blue whales during the late austral winter and early austral spring.

The relative role of the subsurface Southern Ocean in driving negative Antarctic Sea ice extent anomalies in 2016–2021

The low Antarctic sea ice extent following its dramatic decline in late 2016 has persisted over a multiyear period. However, it remains unclear to what extent this low sea ice extent can be attributed to changing ocean conditions. Here, we investigate the causes of this period of low Antarctic sea ice extent using a coupled climate model partially constrained by observations. We find that the subsurface Southern Ocean played a smaller role than the atmosphere in the extreme sea ice extent low in 2016, but was critical for the persistence of negative anomalies over 2016–2021. Prior to 2016, the subsurface Southern Ocean warmed in response to enhanced westerly winds. Decadal hindcasts show that subsurface warming has persisted and gradually destabilized the ocean from below, reducing sea ice extent over several years. The simultaneous variations in the atmosphere and ocean after 2016 have further amplified the decline in Antarctic sea ice extent.

Oxygen and irradiance constraints on visual habitat in a changing ocean: The luminoxyscape

Oxygen and irradiance constraints on visual habitat in a changing ocean: The luminoxyscape

Projecting species distributions using fishery‐dependent data

AbstractMany marine species are shifting their distributions in response to changing ocean conditions, posing significant challenges and risks for fisheries management. Species distribution models (SDMs) are used to project future species distributions in the face of a changing climate. Information to fit SDMs generally comes from two main sources: fishery‐independent (scientific surveys) and fishery‐dependent (commercial catch) data. A concern with fishery‐dependent data is that fishing locations are not independent of the underlying species abundance, potentially biasing predictions of species distributions. However, resources for fishery‐independent surveys are increasingly limited; therefore, it is critical we understand the strengths and limitations of SDMs developed from fishery‐dependent data. We used a simulation approach to evaluate the potential for fishery‐dependent data to inform SDMs and abundance estimates and quantify the bias resulting from different fishery‐dependent sampling scenarios in the California Current System (CCS). We then evaluated the ability of the SDMs to project changes in the spatial distribution of species over time and compare the time scale over which model performance degrades between the different sampling scenarios and as a function of climate bias and novelty. Our results show that data generated from fishery‐dependent sampling can still result in SDMs with high predictive skill several decades into the future, given specific forms of preferential sampling which result in low climate bias and novelty. Therefore, fishery‐dependent data may be able to supplement information from surveys that are reduced or eliminated for budgetary reasons to project species distributions into the future.

Substantial microbial community shifts in response to an exceptional harmful algal bloom in coastal Southern California

Phytoplankton blooms create organic matter that stimulates entire marine ecosystems, including other components of the microbial community. How the ecosystem responds varies depending on the intensity, duration, and composition of the bloom. When the bloom has a direct or indirect negative impact on the ecosystem, it is termed a harmful algal bloom (HAB). HAB frequency is expected to increase in response to changing oceanic conditions and coastal nutrient supply. Characterizing the response of the bacterial and archaeal communities to HABs will improve our understanding of the ecological impacts of these phenomena. We utilized time series of chlorophyll a, phaeophytin, dissolved oxygen, flow cytometry cell counts, and microbial community structure (assessed via 16S rRNA gene sequences) maintained by several observing programs to investigate how the microbial community was affected by an exceptional bloom of Lingulodinium polyedra in coastal Southern California. These multi-year datasets allowed us to compare the microbial community response to past events, such as a smaller L. polyedra bloom the previous year. We demonstrated that the bacterial and archaeal response to the 2020 bloom was unique taxonomically, with many novel heterotrophs, and higher trophic state variance. The measured heterotrophic response to the bloom resulted in massive oxygen drawdown and may have impacted the length of the bloom and contributed to a secondary diatom bloom following the main HAB event. Taken together, these data illustrate how the massive 2020 L. polyedra bloom created unique ecological conditions for coastal Southern California.

Opportunistic diseases in marine eukaryotes: Could Bacteroidota be the next threat to ocean life?

Bacteria within the phylum Bacteroidota (Bacteroidetes) are known to cause devastating and widespread disease outbreaks in marine eukaryotic hosts. However, with few pathogens described in detail, their prevalence and virulence strategies remain largely unknown. Here, we systematically reviewed the literature to evaluate the current understanding of Bacteroidota that cause disease in marine hosts. Isolates affiliated with the genera Tenacibaculum and Aquimarina (Flavobacteriaceae) were the most widely reported and characterized pathogens. Although cultured isolates were predominantly Flavobacteriia, culture-independent studies also found classes Bacteroidia, Cytophagia and Sphingobacteriia associated with disease. We found that pathogenic marine Bacteroidota largely conformed to an opportunistic lifestyle but could also act as secondary pathogens or were involved in polymicrobial diseases. Many diseases were also associated with an environmental stressor, especially those affecting coral, macroalgae and fish. Keyvirulence traitsincluded the production of adhesins and host tissue-degrading enzymes. Overall, the nature of disease involving Bacteroidota pathogens appears to be an outcome of complex host-pathogen-environment interactions; however, our understanding of virulence remains limited by the lack of functional characterization studies. This is concerning as Bacteroidota have the potential to emerge as a serious threat to marine ecosystems and aquaculture industries, driven by global changes in ocean conditions.

Biological sensitivities to high-resolution climate change projections in the California current marine ecosystem.

The California Current Marine Ecosystem is a highly productive system that exhibits strong natural variability and vulnerability to anthropogenic climate trends. Relating projections of ocean change to biological sensitivities requires detailed synthesis of experimental results. Here, we combine measured biological sensitivities with high‐resolution climate projections of key variables (temperature, oxygen, and pCO2) to identify the direction, magnitude, and spatial distribution of organism‐scale vulnerabilities to multiple axes of projected ocean change. Among 12 selected species of cultural and economic importance, we find that all are sensitive to projected changes in ocean conditions through responses that affect individual performance or population processes. Response indices were largest in the northern region and inner shelf. While performance traits generally increased with projected changes, fitness traits generally decreased, indicating that concurrent stresses can lead to fitness loss. For two species, combining sensitivities to temperature and oxygen changes through the Metabolic Index shows how aerobic habitat availability could be compressed under future conditions. Our results suggest substantial and specific ecological susceptibility in the next 80 years, including potential regional loss of canopy‐forming kelp, changes in nearshore food webs caused by declining rates of survival among red urchins, Dungeness crab, and razor clams, and loss of aerobic habitat for anchovy and pink shrimp. We also highlight fillable gaps in knowledge, including specific physiological responses to stressors, variation in responses across life stages, and responses to multistressor combinations. These findings strengthen the case for filling information gaps with experiments focused on fitness‐related responses and those that can be used to parameterize integrative physiological models, and suggest that the CCME is susceptible to substantial changes to ecosystem structure and function within this century.

The MicroClimate Screen – A microscale climate exposure system for assessing the effect of CO2, temperature and UV on marine microalgae

Global warming and anthropogenic activities are changing the ocean, inducing profound impacts on marine life and ecosystems from changing physical and chemical factors in and above the water column. Rising surface temperatures, ocean acidification, and seasonal variations in UV radiation (UVR), modulated by water clarity and sea-ice extent, affect life cycles of the marine food-web, and directly or indirectly also the global carbon fixation. Diatoms, pelagic microalgae that are responsible for 40% of the marine productivity, have limited capability to avoid exposure to changing ocean conditions, and hence, highly relevant for model studies of the influence of climate change on growth and productivity in the marine environment. A plate-based high-throughput exposure system was constructed to assess the biological effects from relevant climate change factors on the diatom Skeletonema pseudocostatum, conducted as a chronic toxicity tests over 72 h periods. The exposure system consisted of a micro-climate unit and a light-exposure unit, enabling accurate regulation of pCO2, temperature, UVR and photosynthetic active radiation (PAR). Changes in physical factors, including pH, dissolved inorganic carbon (DIC), total alkalinity (TA), temperature and salinity in the medium, as well as reduction in growth were characterised to demonstrate performance of the micro exposure system. The results demonstrate that the exposure system successfully simulated ocean acidification and could maintain stable temperature (CV < 3%), PAR and UVR irradiance (CV < 8%). Growth inhibition responses were typically dose-dependent and verified that the micro-exposure system could be used to assess effects and adaptions to climate-relevant stressors.

California shellfish farmers: Perceptions of changing ocean conditions and strategies for adaptive capacity

Coastal communities along the U.S. West Coast experience a myriad of environmental stressors, including exposure to low pH waters exacerbated by ocean acidification (OA). This can result in ecological and social consequences, making necessary the exploration and support for locally relevant strategies to adapt to OA and other environmental changes. The shellfish aquaculture industry along the West Coast is particularly vulnerable to OA, given the negative effects of low pH on shellfish survival and growth. As such, the social-ecological system exemplified by this industry serves as an opportunity to identify and address strategies for local adaptation. Through interviews conducted with West Coast shellfish farm owners and managers (‘growers’), we investigate perceptions of OA and environmental change and identify specific strategies for adaptation. We find that growers are concerned about OA, among many other environmental stressors such as marine pathogens and water temperature. However, growers are often unable to attribute changes in shellfish survival or health to these environmental factors due to a lack of data and the resources and network required to acquire and interpret these data. From these interviews, we identify a list of adaptive strategies growers employ or would like to employ to improve their overall adaptive capacity to multiple stressors (environmental, economic, political), which together, allow farms to weather periods of OA-induced stress more effectively. Very few studies to date have identified specific adaptive strategies derived directly from the communities being impacted. This work therefore fills a gap in the literature on adaptive capacity by amplifying the voices of those on the front lines of climate change and identifying explicit pathways for adaptation.

Time series covering up to four decades reveals major changes and drivers of marine growth and proportion of repeat spawners in an Atlantic salmon population.

Wild Atlantic salmon populations have declined in many regions and are affected by diverse natural and anthropogenic factors. To facilitate management guidelines, precise knowledge of mechanisms driving population changes in demographics and life history traits is needed.Our analyses were conducted on (a) age and growth data from scales of salmon caught by angling in the river Etneelva, Norway, covering smolt year classes from 1980 to 2018, (b) extensive sampling of the whole spawning run in the fish trap from 2013 onwards, and (c) time series of sea surface temperature, zooplankton biomass, and salmon lice infestation intensity.Marine growth during the first year at sea displayed a distinct stepwise decline across the four decades. Simultaneously, the population shifted from predominantly 1SW to 2SW salmon, and the proportion of repeat spawners increased from 3 to 7%. The latter observation is most evident in females and likely due to decreased marine exploitation. Female repeat spawners tended to be less catchable than males by anglers.Depending on the time period analyzed, marine growth rate during the first year at sea was both positively and negatively associated with sea surface temperature. Zooplankton biomass was positively associated with growth, while salmon lice infestation intensity was negatively associated with growth.Collectively, these results are likely to be linked with both changes in oceanic conditions and harvest regimes. Our conflicting results regarding the influence of sea surface temperature on marine growth are likely to be caused by long‐term increases in temperature, which may have triggered (or coincided with) ecosystem shifts creating generally poorer growth conditions over time, but within shorter datasets warmer years gave generally higher growth. We encourage management authorities to expand the use of permanently monitored reference rivers with complete trapping facilities, like the river Etneelva, generating valuable long‐term data for future analyses.

Oceanic conditions in the Barrow Coastal Polynya revealed by a 10-year mooring time series

From 2009 to 2021, continuous mooring observations were conducted within the Barrow Coastal Polynya (BCP) on the northeastern Chukchi Shelf. With a 10-year mooring record (2009–2019), satellite-derived sea-ice production (SIP) data, and atmospheric reanalysis, we confirm that the BCP is a wind-driven hybrid latent and sensible heat polynya forced by northeasterly winds, and we analyze oceanic conditions and their recent changes associated with winter processes such as freeze onset, SIP, and winter-water production. The decade-long record of SIP and warm water upwelling in the BCP is dominated by interannual variability with no discernable long-term trend. In the 2015/2016 season, the SIP reached a record high for the time period studied. Water temperature and salinity prior to the freeze-up period are directly associated with SIP and winter-water production. Although wintertime SIP-related salt input is necessary, autumn salinity is, in some cases, more critical in determining winter water characteristics. The 10-year BCP mooring captures the regional changes in oceanic conditions. Summer-to-autumn ocean temperatures have been increasing as of late, especially since 2016. The prolonged presence of warmer water suggests a direct influence on freeze onset over the Chukchi Shelf and enhanced heat transport into the Arctic basin. In some cases, the upwelled Atlantic-origin warm water also delays freeze onset in the BCP. The 10-year mooring record provides evidence of recent extreme oceanic warming combined with remote and local connections from the Bering to the Chukchi Sea. This collection of data improves understanding of the impact of oceanic changes in Chukchi coastal and inner shelf waters, and regional change in the Pacific Arctic in a rapidly changing climate.