Polar marine invertebrates serve as bellwethers for species vulnerabilities in the face of changing climate at high latitudes of the Earth. Ocean acidification, warming/heatwaves, freshening, sea ice retreat and productivity change are challenges for polar species. Adaptations to life in cold water with intensely seasonal productivity has shaped species traits at both poles. Polar species have life histories often characterised as K-strategist or K-selected (e.g. slow growth and development, larval hypometabolism) that make them sensitive to climate stress and altered seasonal productivity. Moderate warming results in faster development and can have positive effects on development, up to a limit. However, ocean acidification can retard development, impair skeletogenesis and result in smaller larvae. Given the fast pace of warming, data on the thermal tolerance of larvae from diverse species is urgently needed, as well as knowledge of adaptive responses to ocean acidification and changes to sea ice and productivity. Predicted productivity increase would benefit energy-limited reproduction and development, while sea ice loss negatively impacts species with reproduction that directly or indirectly depend on this habitat. It is critical to understand the interactive effects between warming, acidification and other stressors. Polar specialists cannot migrate, making them susceptible to competition and extinction from range-extending subpolar species. The borealisation and australisation of Arctic and Antarctic ecosystems, respectively, is underway as these regions become more hospitable for the larval and adult life-history stages of lower-latitude species. Differences in biogeography and pace of change point to different prospects for Arctic and Antarctic communities. In this Commentary, we hypothesise outcomes for polar species based on life history traits and sensitivity to climate change and suggest research avenues to test our predictions.
Continue reading ‘Climate change and polar marine invertebrates: life-history responses in a warmer, high CO2 world’Posts Tagged 'Arctic'
Climate change and polar marine invertebrates: life-history responses in a warmer, high CO2 world
Published 10 January 2025 Science ClosedTags: Antarctic, Arctic, biological response, review
Ships of Opportunity: crossing the Arctic to investigate the ocean’s uptake of carbon and increasing ocean acidification
Published 7 January 2025 Web sites and blogs ClosedTags: Arctic, chemistry, field
Leticia Barbero, Ph.D., a principal investigator with the Ocean Carbon Cycle group at NOAA’s Atlantic Oceanographic & Meteorological Laboratory (AOML) and a scientist with the University of Miami’s Cooperative Institute of Marine and Atmospheric Studies (CIMAS), traversed the Arctic aboard the ship Le Commandant Charcot. An icebreaking cruise ship, Le Comandant Charcot departed from Nome, Alaska heading to the magnetic North Pole and finally to Svalbard, Norway with a group of 20 scientists from eight countries and over 200 passengers.
While others investigated microplastics, ice cores, and environmental DNA, Leticia collected data as part of the International Ships of Opportunity Program to monitor the global ocean’s uptake of carbon – and ultimately rising acidification in one of the world’s most remote regions.
Carbon dioxide, like all gasses, diffuses between the atmosphere and the ocean. With rising levels of carbon dioxide in the atmosphere, the ocean accumulates more carbon through air-sea gas exchanges as part of its natural cycle. However, rising levels of carbon in the ocean has consequences – and one of them is ocean acidification.
Through partnerships with the Compagnie du Ponant and other cruiseliners, cargo vessels, sailboats, and moorings across private industries, the Ships of Opportunity Program, led in large part by scientists at AOML, enables researchers to track this exchange on a global scale.
An effort supported by NOAA’s Global Ocean Monitoring and Observing program (GOMO), the vast swaths of data collected, quality-controlled and published in the Surface Ocean CO2 Atlas (SOCAT) since these measurements started in the 1960s means researchers across institutions can examine how the ocean’s accumulation of carbon varies regionally, globally, and over years and decades.
However, one region remains understudied where fewer vessels are able to travel and where ocean acidification is occurring faster than the global ocean: the Arctic.
Leticia Barbero, Ph.D. collecting seawater samples through the ice
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In the Charcot’s Wetlab, filters, gas selection valves, and weather sensors merge into a system reading the partial pressure of carbon dioxide (pCO2) in the ambient air and surface waters as the ship and its passengers cruised towards the North Pole. Barbero spent the three weeks onboard running the pCO2 underway system with assistance from the ship’s science support crew as the data was transmitted daily via a satellite modem. The system, installed in April 2022 by scientists at AOML measures the surface ocean’s carbon dioxide concentration continuously as seawater is pumped through it – that is, as long as the pumping system can be kept free of ice, something that is hard to do when the ship is in motion.
To further validate the system’s readings and investigate the Arctic Ocean’s chemistry, Barbero and the team of researchers deployed both CTD and handheld Niskin bottles at predetermined stations along the cruise track, collecting seawater samples at multiple depths from the surface to 900 meters below. And when the ship sat idle, they ventured onto the ice.
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By analyzing these samples back at AOML’s Carbon Lab, the team can measure the pH, alkalinity, and dissolved inorganic carbon as an indicator of ocean acidification, quantify nutrient concentrations that may be encouraging harmful algal blooms in the Arctic, salinity and other key parameters.
Adding to the global array of ships and moorings equipped with pCO2 sensors under the Ships of Opportunity Program, this data builds on an expanding network known as the Surface Ocean CO2 Reference Observing Network (SOCONET) that quantifies the fluctuation of carbon between surface waters and the lowest layer of the atmosphere, the marine boundary layer.
Ultimately a part of the Global Ocean Observing System (GOOS), the expansion of SOCONET allows scientists to monitor the ocean’s sequestration of carbon by more holistically capturing the air-sea gas exchange across time and space – a key factor in determining the annual Global Carbon Budget.
The global ocean has taken up an estimated 26% of anthropogenic carbon – roughly 681 billion metric tonnes of carbon dioxide – emitted into the atmosphere since 1850, effectively mitigating its global warming effect on the climate but also resulting in more acidic waters. In the Arctic, studies suggest sensitivities among key commercial fish species such as the Pacific Cod to rising ocean acidification, making this global effort all the more critical.
Chapter 3 – Arctic environmental processes: the earth system, the Pacific Arctic gateway, and the future of Beringia
Published 1 January 2025 Science ClosedTags: Arctic, review
Arctic environmental processes involve complex interactions among Earth System drivers (e.g., rising surface temperatures), regional responses, and the actions of Arctic residents whose livelihoods depend on the condition of the region’s biophysical systems. This chapter examines these multi-level interactions with particular reference to the Pacific Arctic Gateway, encompassing the marine systems centered on the Bering Strait and the circumstances of residents of the human communities located on the Pribilof Islands in the Bering Sea. The result is an analysis of environmental processes that highlights key issues in Beringia and offers a way of thinking about environmental processes in other parts of the Arctic.
Continue reading ‘Chapter 3 – Arctic environmental processes: the earth system, the Pacific Arctic gateway, and the future of Beringia’Arctic Ocean acidification and carbonate undersaturation enhanced by coastal permafrost erosion
Published 31 December 2024 Science ClosedTags: Arctic, biogeochemistry, modeling, regionalmodeling
Increasing atmospheric CO2 drives ocean acidification, with some of the fastest rates observed on Arctic shelves. Lowest pH levels occur near the coasts due to the additional effects of land-derived carbon sources. However, the impact of anthropogenic climate change on seawater acidity mediated by increasing permafrost thaw and coastal erosion remains unknown. Here, we find that the increase in organic matter release by coastal permafrost erosion over the 20th century enhances the interannual variability of seawater pH in Arctic near-shore areas. As a consequence, carbonate undersaturation events, stressing marine ecosystems, become more frequent, intense, and longer-lasting. We account for synergistic effects of anthropogenic climate change by combining increasing atmospheric CO2 levels and coastal erosion rates, utilizing a novel global model with high-resolution grid refinement towards coastal regions and improved process representation of shelf-specific carbon dynamics. By considering the role of coastal permafrost erosion, we conclude that critical Arctic Ocean acidification states will emerge earlier than simulated by the current generation of Earth system models. Our results emphasize the importance of understanding permafrost-ocean interactions and their increasing impact on marine ecosystems, especially in the rapidly changing Arctic region.
Continue reading ‘Arctic Ocean acidification and carbonate undersaturation enhanced by coastal permafrost erosion’Climate covariate choice and uncertainty in projecting species range shifts: a case study in the Eastern Bering Sea
Published 26 December 2024 Science ClosedTags: Arctic, biological response, crustaceans, field, fish, fisheries, modeling, multiple factors, oxygen, regionalmodeling, temperature
Species distribution models (SDMs) are critical to the adaptive management of fisheries under climate change. While many approaches projecting marine species range shifts have incorporated the effects of temperature on movement, there is a need to incorporate a wider suite of ecologically relevant predictors as temperature-based SDMs can considerably under- or over-estimate the rate of species responses to climate shocks. As a subarctic ecosystem at the sea ice margin, the Eastern Bering Sea (EBS) is warming faster than much of the global ocean, resulting in the rapid redistribution of key fishery and subsistence resources. To support long-term planning and adaptation, we combine 40 years of scientific surveys with a high-resolution oceanographic model to examine the effects of bottom temperature, oxygen, pH and a regional climate index (the extent of the EBS ‘cold pool’) on range projections through the end of the century. We use multimodel inference to partition uncertainty among earth systems models, climate scenarios and distribution model parameterizations for several ecologically and economically important EBS groundfish and crabs. Covariate choice is the primary source of uncertainty for most species, with models that account for spatial responses to the cold pool performing better and suggesting more extensive northward movements than alternative models. Models suggest declines in the probability of occurrence at low pH and oxygen concentrations for most species. We project shifts that are directionally consistent with, yet larger than those previously estimated for most species, suggesting that accounting for large-scale climate variability in species distribution models may substantially alter range projections.
Continue reading ‘Climate covariate choice and uncertainty in projecting species range shifts: a case study in the Eastern Bering Sea’A regional physical-biogeochemical ocean model for marine resource applications in the Northeast Pacific (MOM6-COBALT-NEP10k v1.0)
Published 25 December 2024 Science ClosedTags: Arctic, biogeochemistry, biological response, field, modeling, North Pacific, regionalmodeling, zooplankton
Regional ocean models enable generation of computationally-affordable and regionally-tailored \ ensembles of near-term forecasts and long-term projections of sufficient resolution to serve marine resource management. Climate change, however, has created marine resource challenges, such as shifting stock distributions, that cut across domestic and international management boundaries and have pushed regional modeling efforts toward “coastwide” approaches. Here we present and evaluate a multidecadal hindcast with a Northeast Pacific (NEP) regional implementation of the Modular Ocean Model version 6 with sea ice and biogeochemistry that extends from the Chukchi Sea to the Baja California Peninsula at 10-km horizontal resolution (MOM6-COBALT-NEP10k, or “NEP10k”). This domain includes an Arctic-adjacent system with a broad shallow shelf seasonally covered by sea ice (the Eastern Bering Sea, EBS), a sub-Arctic system with upwelling in the Alaska Gyre and predominant downwelling winds and large freshwater forcing along the coast (the Gulf of Alaska, GoA), and a temperate, eastern boundary upwelling ecosystem (the California Current Ecosystem, CCE). The coastwide model was able to recreate seasonal and cross-ecosystem contrasts in numerous ecosystem-critical properties including temperature, salinity, inorganic nutrients, oxygen, carbonate saturation states, and chlorophyll. Spatial consistency between modeled quantities and observations generally extended to plankton ecosystems, though small to moderate biases were also apparent. Fidelity with observed zooplankton biomass, for example, was limited to first-order seasonal and cross-system contrasts. Temporally, simulated monthly surface and bottom temperature anomalies in coastal regions (< 500m deep) closely matched estimates from data-assimilative ocean reanalyses. Performance, however, was reduced in some nearshore regions coarsely resolved by the model’s 10-km resolution grid, and the time series of satellite-based chlorophyll anomaly estimates proved more difficult to match than temperature. System-specific ecosystem indicators were also assessed. In the EBS, NEP10k robustly matched observed variations, including recent large declines, in the area of the summer bottom water “cold pool” (< 2 °C) which exerts a profound influence on EBS fisheries. In the GoA, the simulation captured patterns of sea surface height variability and variations in thermal, oxygen and acidification risk associated with local modes of inter-annual to decadal climate variability. In the CCE, the simulation robustly captured variations in upwelling indices and coastal water masses, though discrepancies in the latter were evident in the Southern California Bight. Enhanced model resolution may reduce such discrepancies, but any benefits must be carefully weighed against computational costs given the intended use of this system for ensemble predictions and projections. Meanwhile, the demonstrated NEP10k skill level herein, particularly in recreating cross-ecosystem contrasts and the time variation of ecosystem indicators over multiple decades, suggests considerable immediate utility for coastwide retrospective and predictive applications.
Continue reading ‘A regional physical-biogeochemical ocean model for marine resource applications in the Northeast Pacific (MOM6-COBALT-NEP10k v1.0)’Climate change driven effects on transport, fate and biogeochemistry of trace element contaminants in coastal marine ecosystems
Published 24 October 2024 Science ClosedTags: Arctic, biogeochemistry, policy
Human activities and climate change substantially threaten coastal areas, impacting ecosystem functions, services, and human-wellbeing. Trace elements, from both natural and anthropogenic sources, can contaminate coastal regions, and at high concentrations may become toxic to marine biota. Climate change is likely to affect the sources, sinks and cycling of trace elements in coastal systems: for example, riverine runoff is set to increase as precipitation in the Arctic intensifies, and more frequent extreme floods are expected to activate previously deeply buried trace elements. Furthermore, changes in human activity under a warming climate, such as increased Arctic shipping and potential geoengineering projects such as ocean alkalinity enhancement, will likely introduce more trace elements to coastal ecosystems. Advancing our understanding of trace element cycling is at present limited by factors including lack of data coverage in the Global South, challenges in studying multi-stressor effects and ecosystem responses, lack of long-term data, and the difficulty in parametrizing robust models in coastal environments.
Continue reading ‘Climate change driven effects on transport, fate and biogeochemistry of trace element contaminants in coastal marine ecosystems’Shelf-to-basin shuttle of highly fractionated chromium isotopes in the Arctic Ocean
Published 1 October 2024 Science ClosedTags: Arctic, chemistry
The oceanic chromium (Cr) cycle is mainly governed by the interconversion and the distribution of Cr(VI) and Cr(III) species and their stable isotopic ratios (δ53Cr) in the water column. As a result, the Cr cycle generates a strong correlation between the natural logarithm of its dissolved concentration and δ53Cr regardless of the location of sampling. A few studies have reported the Cr composition of certain regions falling off the global Cr array, highlighting the local prevalence of underlying mechanisms participating in the Cr cycle in the oceans. In an effort to better constrain the global Cr array, this study presents an extensive dataset for total dissolved Cr concentration ([Cr]T) and δ53Cr in the Arctic Ocean in regions meeting the environmental conditions where Cr was observed to fall off the global Cr array (e.g. continental shelves, restricted water circulation, sea ice melting). We find that more than 70% of the Arctic seawater collected plot below the global Cr array due to a small addition of highly fractionated Cr (−2.8 ‰ to −1.1 ‰) and its transport across all the Arctic regions sampled. We identify the Chukchi Shelf as the region where highly fractionated Cr is produced, from where a Cr shuttle could work in tandem with the Arctic Fe and Mn shuttles to explain the production and widespread export of isotopically light Cr in the Arctic waters. We identify a second non-reductive release of highly fractionated Cr in the Canadian Arctic Archipelago, Baffin Bay and potentially the Labrador Sea via sediment resuspension, alongside addition of isotopically light Cr originating from crustal rocks. These findings demonstrate that the Arctic-modified outflow signature of Cr isotopes modify the Cr isotopic signature of the North Atlantic waters, and that the North Atlantic waters may deviate from the global Cr array depending on whether the isotopically light Cr added to the Arctic Ocean is Cr(III) that has not been scavenged or Cr(III) that has oxidized to Cr(VI).
Continue reading ‘Shelf-to-basin shuttle of highly fractionated chromium isotopes in the Arctic Ocean’Off-shelf transport and biogeochemical cycling of terrestrial organic carbon along the East Siberian continental margin
Published 23 September 2024 Science ClosedTags: Arctic, biogeochemistry, chemistry, sediment
Continental margins receive, process and sequester most of the terrestrial organic carbon (terrOC) released into the ocean. In the Arctic, increasing fluvial discharge and collapsing permafrost are expected to enhance terrOC release and degradation, leading to ocean acidification and translocated CO2 release to the atmosphere. However, the processes controlling terrOC transport beyond the continental shelf, and the amount of terrOC that reaches the slope and the rise are poorly described. Here we study terrOC transport to the Laptev Sea continental slope and rise by probing surface sediments with dual-isotope (δ13C/Δ14C) source apportionment, degradation-diagnostic terrestrial biomarkers (n-alkanes, n-alkanoic acids, lignin phenols) and 210Pbxs-based mass accumulation rates (MAR). The MAR-terrOC (g m−2 yr−1) decrease from 14.7 ± 12.2 on the shelf, to 7.0 ± 5.8 over the slope, to 2.3 ± 0.3 for the rise. Scaling this to the respective regimes yields that 80% of the terrOC accumulates on the shelf, while 11% and 9% of the accumulation occurs in slope and rise sediments, respectively. TerrOC remineralization is evidenced by biomarker degradation proxies (CPI of n-alkanes and 3,5Bd/V) indicating 40% and 60% more terrOC degradation from slope to rise, consistent with a decline in terrOC concentrations by 57%. TerrOC degradation only partially explains this decline. An updated Laptev Sea terrOC budget suggests that sediment transport dynamics such as turbidity currents may drive terrOC shelf-basin export, contributing to the observed accumulation pattern. This study quantitatively demonstrates that Arctic shelf seas are key receptor systems for remobilized terrOC, emphasizing their importance in the carbon cycle of the rapidly changing Arctic.
Key Points
- Terrestrial carbon export from the Laptev Sea shelf to the slope and rise is studied using δ13C/Δ14C, biomarkers and 210Pb mass accumulation
- The accumulation of terrestrial carbon declines by 52% at the shelf edge and by 68% from slope to rise due to transport and degradation dynamics
- A terrestrial carbon budget for the Laptev Sea suggests 80%–90% of the input is retained on the shelf via accumulation and re-mineralization
A spatiotemporal analysis of ocean acidification in the Pacific-Arctic region
Published 16 August 2024 Science ClosedTags: Arctic, chemistry, North Pacific
The Pacific-Arctic Region (PAR) is highly vulnerable to ocean acidification (OA)due to its low buffer capacity, carbonate concentration, and the regionally-amplifiedeffects of climate change. Although it experiences the highest rates of OA globally, the existing literature lacks observation-based surface decadal OA rates forthe PAR, primarily due to large data gaps. To address these limitations, we aggregated open-source carbonate datasets and established spatially-dependent relationships to predict surface total alkalinity (TA) using salinity and temperature (R2=0.93, MAE = 23 µmol kg−1). We then applied these relationships to gridded sea surface salinity and temperature products to obtain monthly surface TA fields. The TA fields were coupled with the MPI-SOM-FFN surface pCO2 dataset (doi: 10.7289/v5z899n6) to obtain monthly 1°x 1° surface pH, ΩAr, and dissolved inorganic carbon fields from 1993-2021 for the entire PAR, yielding the first gapless gridded Arctic carbonate system dataset to date. This dataset indicated that the Southern PAR acidified at rates comparable to the global average, predominantly due to the absorption of anthropogenic CO2. In contrast, the Bering Sea shelf exhibited basification, likely a result of increased primary productivity. The Northern PAR exhibited acidification rates 2-4x greater than the global rate due to reduced TA linked to sea ice melt. Our findings suggest that continued warming will likely exacerbate surface acidification in regions experiencing a shift from yearround multi-year ice cover to a seasonal ice pack. While local processes such as primary productivity can temporarily counteract OA, whether they can compensate for rising anthropogenic CO2 levels is unclear. This highlights the complexity of predicting future ocean acidification trends and underscores the importance of advanced models that integrate both climatic and biological factors, enabling accurate forecasts of impacts on marine ecosystems in these highly sensitive regions
Continue reading ‘A spatiotemporal analysis of ocean acidification in the Pacific-Arctic region’How much can riverine biogeochemical fluxes affect the arctic ocean acidification?
Published 19 June 2024 Science ClosedTags: Arctic, biogeochemistry, chemistry, methods, modeling, regionalmodeling
Abstract
Arctic rivers carry not only large amounts of freshwater but also biogeochemical materials into the ocean and play important roles in Arctic ocean acidification (OA). This study quantitatively evaluated the effects of riverine biogeochemical fluxes (R-BGC; carbon and nutrients) on the Arctic marine carbonate system and OA using multi-decadal experiments (1979–2018) with a pan-Arctic sea ice–ocean model. Improved initial and lateral boundary conditions of carbonate properties, observation-based riverine biogeochemical data, and land model-based interannually varying riverine freshwater discharge were adopted to enable more realistic experiments. The model simulated negative trends in aragonite saturation state (Ω) and pH in most regions of Arctic Ocean regardless of R-BGC. The increased riverine freshwater promoted more OA through the higher dilution effect. Compared to the experiment with riverine discharge of only freshwater, the inclusion of R-BGC caused positive anomalies in Ω and pH (by ∼0.14 and ∼0.03 in central basins, and by ∼0.15 and ∼0.06 in shelf seas, respectively). In the central basins, these anomalies were caused mostly by carbon (total alkalinity and dissolved inorganic carbon) of the R-BGC. In the shelf seas, nutrient (nitrate and silicate) fluxes also contributed ∼14% and ∼32% of the anomalies owing to the enhanced primary production and a corresponding reduction in seawater pCO2. R-BGC mitigated OA (ΔΩ = −1.53 × 10−3 year−1 and ΔpH = −0.56 × 10−3 year−1) in regions where riverine freshwater was accumulated (i.e., the Canada Basin, Chukchi Cap, Eurasian Basin, and East Siberian Sea). This study stressed the importance of including R-BGC for OA model projection.
Key Points
- Simulations with only riverine freshwater overestimate Arctic ocean acidification and negative trends in aragonite saturation state and pH
- Addition of riverine biogeochemical fluxes, especially total alkalinity and dissolved inorganic carbon, can reduce this overestimation
- Riverine nutrient fluxes can also reduce ∼14% and ∼32% of the overestimation in aragonite saturation state and pH in shelf seas
Plain Language Summary
Ocean acidification (OA) is caused primarily by atmospheric CO2 absorption at the sea surface. In the Arctic Ocean, riverine biogeochemical inputs (R-BGC; carbon and nutrients carried by riverine water), in addition to freshwater discharge, affect OA. This study quantified the effects of R-BGC on OA using a couple of model simulations for 1979–2018. Advancing from previous studies, this study conducted more realistic experiments by using improved initial and lateral boundary conditions of carbonate properties, observation-based riverine biogeochemical data, and the land model-based interannually varying riverine freshwater discharge data. R-BGC impacts on OA were found mainly in the surface waters of the Arctic, especially in coastal regions close to the river mouths. During 1989–2018, negative trends in carbonate saturation state and pH (both indicating OA) were simulated regardless of R-BGC in most regions of Arctic Ocean. Compared to a simulation with riverine input of only freshwater, R-BGC mitigated the simulated OA in the regions with increased riverine freshwater content. This study stressed the importance of R-BGC for model-based OA estimation and future projections. It will improve the understanding of OA under climate change and aid in informing marine ecosystem-based management.
Continue reading ‘How much can riverine biogeochemical fluxes affect the arctic ocean acidification?’The combined effects of warming, ocean acidification, and fishing on the northeast Atlantic cod (Gadus morhua) in the Barents Sea
Published 19 April 2024 Science ClosedTags: Arctic, fisheries, methods, modeling, regionalmodeling
With a biomass of ∼4 million tonnes, and annual catches of 900 000 tonnes, the northeast Atlantic (NEA) cod stock in the Barents Sea is the world’s largest. Scientists have been trying to explain the variability in recruitment of this stock for over 100 years, in particular connecting it to spawning stock biomass and environmental factors such as temperature. It has been suggested that the combination of ocean acidification and global warming will lead to a significant decrease in the spawning stock biomass and an eventual (end of this century) collapse of the NEA cod stock in the Barents Sea. We show that a temperature- and OA-driven decline in recruits will likely lead to a smaller cod stock, but not to a collapse. Instead, the level of fishing pressure and, not least, the choice of the recruitment function applied in simulations and how it relates to temperature, is extremely important when making such forecasts. Applying a non-linear relationship between temperature and spawning stock biomass—as has been done in studies that predict a collapse of the NEA cod stock—does not improve accuracy and, in addition, adds a large decrease in number of recruits that is not biologically supported.
Continue reading ‘The combined effects of warming, ocean acidification, and fishing on the northeast Atlantic cod (Gadus morhua) in the Barents Sea’Anthropogenic climate change drives non-stationary phytoplankton internal variability
Published 19 March 2024 Science ClosedTags: Arctic, biological response, globalmodeling, modeling, North Atlantic, North Pacific, phytoplankton, regionalmodeling
Earth system models suggest that anthropogenic climate change will influence marine phytoplankton over the coming century with light-limited regions becoming more productive and nutrient-limited regions less productive. Anthropogenic climate change can influence not only the mean state but also the internal variability around the mean state, yet little is known about how internal variability in marine phytoplankton will change with time. Here, we quantify the influence of anthropogenic climate change on internal variability in marine phytoplankton biomass from 1920 to 2100 using the Community Earth System Model 1 Large Ensemble (CESM1-LE). We find a significant decrease in the internal variability of global phytoplankton carbon biomass under a high emission (RCP8.5) scenario and heterogeneous regional trends. Decreasing internal variability in biomass is most apparent in the subpolar North Atlantic and North Pacific. In these high-latitude regions, bottom-up controls (e.g., nutrient supply, temperature) influence changes in biomass internal variability. In the biogeochemically critical regions of the Southern Ocean and the equatorial Pacific, bottom-up controls (e.g., light, nutrients) and top-down controls (e.g., grazer biomass) affect changes in phytoplankton carbon internal variability, respectively. Our results suggest that climate mitigation and adaptation efforts that account for marine phytoplankton changes (e.g., fisheries, marine carbon cycling) should also consider changes in phytoplankton internal variability driven by anthropogenic warming, particularly on regional scales.
Continue reading ‘Anthropogenic climate change drives non-stationary phytoplankton internal variability’Sea-ice loss accelerates carbon cycling and enhances seasonal extremes of acidification in the Arctic Chukchi Sea
Published 4 March 2024 Science ClosedTags: Arctic, chemistry, field
The Chukchi Sea shelf (CSS) is a highly productive region in the Arctic Ocean and it is highly efficient for absorbing atmospheric carbon dioxide and exporting and retaining carbon in the deep sea. However, with global warming, the carbon retention time in CSS may decrease, leading to less efficient carbon export. Here, we investigate the seasonal variability of carbonate chemistry in CSS using three sets of late- vs. early-summer reoccupations of the same transect. Our findings demonstrate substantially increased and rapid degradation of biologically produced organic matter and therefore acidification over time in the southern CSS due to earlier sea-ice retreat, resulting in significantly shorter carbon retention time. In sharp contrast, no increased degradation has been observed in the northern CSS where photosynthesis has just commenced. In the future, climate change would further diminish the carbon export capacity and exacerbate seasonal acidification not only within CSS but also across other polar coastal oceans.
Continue reading ‘Sea-ice loss accelerates carbon cycling and enhances seasonal extremes of acidification in the Arctic Chukchi Sea’Trends and projections in climate-related stressors impacting Arctic marine ecosystems – a CMIP6 model analysis
Published 4 March 2024 Science ClosedTags: Arctic, chemistry, modeling, regionalmodeling
Eleven Earth System Models (ESMs) contributing to the Coupled Model Intercomparison Project (CMIP6) were evaluated with respect to climate-related stressors impacting Arctic marine ecosystems (temperature, sea ice, oxygen, ocean acidification). Stressors show regional differences and varying differences over time and space among models. Trend magnitudes increase over time and are highest by end-of-century for temperature and O2. Differences between scenarios SSP2-4.5 and SSP5-8.5 for these variables vary among models and regions, mainly driven by sea-ice retreat. Differences in biogeochemical parameterizations contribute to acidification differences. Projections indicate consistent ocean acidification until 2040 and faster progression for the higher emission scenario thereafter. For SSP5-8.5 all Arctic regions show aragonite undersaturation by 2080, and calcite undersaturation for all but two regions by 2100 for all models. Most regions can avoid calcite undersaturation with lower emissions (SSP2-4.5). All variables show increases in seasonal amplitude, most prominently for temperature and oxygen. Calcium carbonate saturation state (Ω) shows little change to the seasonal range and a suggestion of temporal shifts in extrema. Seasonal changes in Ω may be underestimated due to lacking carbon cycle processes within sea ice in CMIP6 models. The analysis emphasizes regionally varying threats from multiple stressors on Arctic marine ecosystems and highlights the propagation of uncertainties from sea ice to temperature and biogeochemical variables. Large model differences in seasonal cycles emphasize the need for improved model constraints, predominantly the representation of sea-ice decline, to enhance the applicability of CMIP models in multi-stressor impacts assessments.
Continue reading ‘Trends and projections in climate-related stressors impacting Arctic marine ecosystems – a CMIP6 model analysis’Carbonate chemistry and carbon sequestration driven by inorganic carbon outwelling from mangroves and saltmarshes
Published 2 January 2024 Science ClosedTags: Arctic, chemistry, field, Indian, North Atlantic, North Pacific, South Atlantic, South Pacific
Mangroves and saltmarshes are biogeochemical hotspots storing carbon in sediments and in the ocean following lateral carbon export (outwelling). Coastal seawater pH is modified by both uptake of anthropogenic carbon dioxide and natural biogeochemical processes, e.g., wetland inputs. Here, we investigate how mangroves and saltmarshes influence coastal carbonate chemistry and quantify the contribution of alkalinity and dissolved inorganic carbon (DIC) outwelling to blue carbon budgets. Observations from 45 mangroves and 16 saltmarshes worldwide revealed that >70% of intertidal wetlands export more DIC than alkalinity, potentially decreasing the pH of coastal waters. Porewater-derived DIC outwelling (81 ± 47 mmol m−2 d−1 in mangroves and 57 ± 104 mmol m−2 d−1 in saltmarshes) was the major term in blue carbon budgets. However, substantial amounts of fixed carbon remain unaccounted for. Concurrently, alkalinity outwelling was similar or higher than sediment carbon burial and is therefore a significant but often overlooked carbon sequestration mechanism.
Continue reading ‘Carbonate chemistry and carbon sequestration driven by inorganic carbon outwelling from mangroves and saltmarshes’Future warming stimulates growth and photosynthesis in an Arctic microalga more strongly than changes in light intensity or pCO2
Published 20 December 2023 Science ClosedTags: Arctic, biological response, growth, laboratory, light, multiple factors, photosynthesis, physiology, phytoplankton, primary production, temperature
We assessed the responses of solitary cells of Arctic Phaeocystis pouchetii grown under a matrix of temperature (2°C vs. 6°C), light intensity (55 vs. 160 μmol photons m−2 s−1) and pCO2 (400 vs. 1000 μatm CO2, i.e., 40.5 vs. 101.3 Pa). Next to acclimation parameters (growth rates, particulate and dissolved organic C and N, Chlorophyll a content), we measured physiological processes in vivo (electron transport rates and net photosynthesis) using fast-repetition rate fluorometry and membrane-inlet mass spectrometry. Within the applied driver ranges, elevated temperature had the most pronounced impacts, significantly increasing growth, elemental quotas and photosynthetic performance. Light stimulations manifested more prominently under 6°C, underlining temperature’s role as a “master-variable”. pCO2 was the least effective driver, exerting mostly insignificant effects. The obtained data were used for a simplistic upscaling simulation to investigate potential changes in P. pouchetii‘s bloom dynamics in the Fram Strait with increasing temperatures over the 21st century. Although solitary cells might not be fully representative of colonial cells commonly observed in the field, our results suggest that global warming accelerates bloom dynamics, with earlier onsets of blooms and higher peak biomasses. Such a temperature-induced acceleration in the phenology of Phaeocystis and likely other Arctic phytoplankton might cause temporal mismatches, e.g., with the development of grazers, and therefore substantially affect the biogeochemistry and ecology of the Arctic.
Continue reading ‘Future warming stimulates growth and photosynthesis in an Arctic microalga more strongly than changes in light intensity or pCO2’Planktonic foraminifers and shelled pteropods in the Barents Sea: seasonal distribution and contribution to the carbon pump of the living fauna, and foraminiferal development during the last three millennia
Published 30 November 2023 Science ClosedTags: abundance, Arctic, biological response, BRcommunity, community composition, field, morphology, otherprocess, paleo, protists, sediment
The Arctic Ocean in general and the Barents Sea specifically, are highly affected by the human induced carbon dioxide (CO2) emissions and increasing temperatures. Atlantification, caused by an increase in warm Atlantic Water inflow, and polar amplification, caused by a higher impact of the increasing temperatures at high latitudes, have already been observed. Moreover, the Barents Sea has been described as a hotspot for ocean acidification. Ocean acidification is the decrease of pH, calcium carbonate saturation state, and carbonate ion concentration due to an increase in CO2 uptake from the atmosphere by the ocean. This alteration of the carbonate chemistry of the water affects the marine biota, especially planktonic marine calcifiers. They are organisms living in the water column with a shell made of calcium carbonate (CaCO3). They contribute significantly to the carbon cycle by exporting mainly CaCO3 from the surface water to the seabed when they die. The main goal of this thesis is to study the distribution of marine calcifiers (planktonic foraminifers and shelled pteropods) in the Barents Sea and the adjacent Arctic Basin. We have (1) investigated their distribution patterns and contribution to carbon dynamics in the north Svalbard margin and in a seasonal basin in the northern Barents Sea; and (2) reconstructed the foraminiferal production and preservation patterns from the late Holocene in sediment cores from the northern and southern Barents Sea. The results from this thesis show that pteropods are important contributors to the carbon dynamics in all seasons in the northern Barents Sea and northern Svalbard margin. Due to the higher sensitivity of their shells compared to foraminifers, they are more likely to be affected by ocean acidification. Moreover, the abundance of foraminifers in the sediment suggests higher productivity in the southern than in the northern Barents Sea. The almost zero abundances observed in the northern Barents Sea core, combined with the seasonality of marine calcifiers, the water carbonate chemistry, and the presence of agglutinated foraminifers suggest dissolution of CaCO3 in the sediment. Due to the use of their shells in paleoceanography, further investigations of CaCO3 dissolution are needed to use them as proxies for the reconstruction of the paleoenvironmental and paleoclimatic conditions in the Barents Sea.
Continue reading ‘Planktonic foraminifers and shelled pteropods in the Barents Sea: seasonal distribution and contribution to the carbon pump of the living fauna, and foraminiferal development during the last three millennia’Editorial: the changing carbonate systems in coastal, estuarine, shelf areas and marginal seas
Published 23 November 2023 Science ClosedTags: Antarctic, Arctic, biogeochemistry, biological response, chemistry, corals, North Pacific, review
Editorial on the Research Topic
The changing carbonate systems in coastal, estuarine, shelf areas and marginal seas
Global atmospheric CO2 concentrations have increased from 320 ppm in the 1960s to the present-day value of 420 ppm, primarily due to anthropogenic activities. This increase influences the seawater carbonate system, impacting the marine ecosystem. There are still gaps that need to be resolved for predicting how these marine systems respond to current and future CO2 levels. Any actions to mitigate the change in pH will require adaptive management of multiple stressors across several spatial scales. Combined, these perspectives yield a more comprehensive picture of events during ocean acidification (OA).
This Research Topic brings together articles from different regions, including coastal, estuarine, and shelf areas and marginal seas, all susceptible to changing atmospheric conditions, riverine inputs, air-sea CO2 exchanges, and multiple acid-base reactions that can alter carbonate chemistry. Articles on the long-term trends of CO2 system descriptors and the interactions with calcifying organisms were also sought. The present Research Topic is primarily based on original articles devoted to carbonate systems in the marginal seas, but it is a pity that some interesting papers dealing with freshwater inflows, estuaries, and related coastal areas were not accepted.
Fransson et al. examined the effects of glacial and sea-ice meltwater on ocean acidification in the waters near the 79 North Glacier (79 NG) and the northeast Greenland shelf. The researchers investigated various ocean acidification factors and the influence of freshening, primary production, and air-sea CO2 exchange. One of the key findings was that the biological removal of CO2 through primary production played a crucial role in offsetting the negative impact of freshwater dilution on the aragonite saturation state (ΩAr), which is a measure of ocean acidification. This compensation effect was most pronounced in 2012, especially in the vicinity of the 79 NG front, where there was a significant presence of glacial meltwater and surface stratification. In 2016, a different scenario was observed, with a more homogenized water column due to sea-ice meltwater. In this case, the compensation effect of biological CO2 removal on ΩAr was weaker compared to 2012. The study also suggests that in the future, with ongoing climate and ocean chemistry changes, the increasing influence of meltwater may surpass the mitigating effects of biological CO2 removal. This could lead to unfavorable conditions for organisms that rely on calcium carbonate for their shells and skeletons. Thus, all the proposed factors need to be closely monitored as they could have significant implications for marine ecosystems and calcifying organisms in the face of ongoing environmental changes.
Continue reading ‘Editorial: the changing carbonate systems in coastal, estuarine, shelf areas and marginal seas’Water structure and carbon dioxide flux over the Laptev Sea continental slope and in the Vilkitsky Strait in the autumn season
Published 17 November 2023 Science ClosedTags: Arctic, chemistry, field
Within the program “Ecosystems of the Siberian Arctic Seas,” carried out by Shirshov Institute of Oceanology, Russian Academy of Sciences since 2007, studies of the water structure and spatial variability of the parameters of the carbonate system have been performed, and the intensity and direction of the carbon dioxide flux over the continental slope of the Laptev Sea and in the Vilkitsky Strait in September 2018 have been calculated. The presence of several main water masses that govern the water structure in the study area is shown. A strong spatial variability of the parameters of the carbonate system of seawater, determined by complexes of physical and chemical–biological processes, has been revealed. The intensity and direction of the carbon dioxide flux at the water–atmosphere boundary were calculated, which range from –12 to 4 mmol m–2 day–1. It was revealed that the investigated area of the outer shelf and continental slope of the Laptev Sea is an emitter of carbon dioxide into the atmosphere as of September 2018. Conversely, the area of the Vilkitsky Strait, is a CO2 sink zone.
Continue reading ‘Water structure and carbon dioxide flux over the Laptev Sea continental slope and in the Vilkitsky Strait in the autumn season’
