More Like this

1. Analysis of Satellite and In Situ Optical Proxies for PIC and POC During GEOTRACES GP15 and GP17‐OCE Transects From the Subarctic North Pacific to the Southern Ocean

   https://doi.org/10.1029/2024EA004070  

   Li, Yunhao; Bishop, James_K_B; Lam, Phoebe_J; Ohnemus, Daniel_C (April 2025, Earth and Space Science)

   Abstract The biological pump, a fundamental process governing atmospheric CO₂, rapidly transfers particulate inorganic and organic carbon (PIC and POC) from surface waters to the deep sea but is inherently highly variable in space and time, and thus poorly observed. Here we synthesize PIC and POC data from satellites, CTD‐profiled optical sensors (birefringence and transmissometer), and from in situ pumps samples from GEOTRACES transects spanning 20,000 km from the North Pacific to Southern Ocean. High resolution profile data from PIC sensors revealed strong subsurface maxima in the deepest euphotic zone waters of oligotrophic gyres; furthermore, data showed high concentrations of PIC penetrating to >500 m south of the Subarctic Front (45°N–35°N), at the equator, and north of the Antarctic Polar Front (45°S–55°S) indicating high carbon export in these regions. We developed a new temporal/spatial interpolation scheme for satellite data that improved matchups with ship observations. North of the Antarctic Polar Front (APF), PIC sensor data was generally well aligned with sample PIC; however, a positive bias of satellite PIC was found in poor retrieval regions. South of the APF, both satellite and birefringence sensor greatly overestimated PIC by factors of >25 and 12, respectively, compared to sample PIC which averaged 15 nM. The unanticipated discovery of a non‐carbonate particle birefringence source coupled with a microscopic investigation of pump samples leads us to hypothesize that internal reflection within bubbles and/or cellular structures of heavily silicified colony‐forming diatoms (FragilariopsisandPseudo‐nitzschia) is the cause for anomalous birefringence and adds to backscattered satellite radiances. 

   more » « less
2. Carbon export and fate beneath a dynamic upwelled filament off the California coast

   https://doi.org/10.5194/bg-18-3053-2021  

   Bourne, Hannah L.; Bishop, James K.; Connors, Elizabeth J.; Wood, Todd J. (January 2021, Biogeosciences)

   null (Ed.)

   Abstract. To understand the vertical variations in carbon fluxes inbiologically productive waters, four autonomous carbon flux explorers(CFEs), ship-lowered CTD-interfaced particle-sensitive transmissometer andscattering sensors, and surface-drogued sediment traps were deployed in afilament of offshore flowing, recently upwelled water, during the June 2017California Current Ecosystem – Long Term Ecological Research process study.The Lagrangian CFEs operating at depths from 100–500 m yielded carbon fluxand its partitioning with size from 30 µm–1 cm at three intensivestudy locations within the filament and in waters outside the filament. Sizeanalysis codes intended to enable long-term CFE operations independent ofships are described. Different particle classes (anchovy pellets, copepodpellets, and > 1000 µm aggregates) dominated the 100–150 mfluxes during successive stages of the filament evolution as it progressedoffshore. Fluxes were very high at all locations in the filament; below150 m, flux was invariant or increased with depth at the two locationscloser to the coast. Martin curve b factors (± denotes 95 %confidence intervals) for total particulate carbon flux were +0.37 ± 0.59, +0.85 ± 0.31, −0.24 ± 0.68, and −0.45 ± 0.70 at thethree successively occupied locations within the plume, and in transitionalwaters. Interestingly, the flux profiles for all particles< 400 µm were a much closer fit to the canonical Martinprofile (b−0.86); however, most (typically > 90 %) ofthe particle flux was carried by > 1000 µm sized aggregateswhich increased with depth. Mechanisms to explain the factor of 3 fluxincrease between 150 and 500 m at the mid-plume location are investigated. 

   more » « less
3. Environmental Drivers of Coccolithophore Growth in the Pacific Sector of the Southern Ocean

   https://doi.org/10.1029/2023GB007751  

   Oliver, H.; McGillicuddy, Jr., D. J.; Krumhardt, K. M.; Long, M. C.; Bates, N. R.; Bowler, B. C.; Drapeau, D. T.; Balch, W. M. (November 2023, Global Biogeochemical Cycles)

   Abstract The Great Calcite Belt (GCB) is a band of high concentrations of suspended particulate inorganic carbon (PIC) spanning the subantarctic Southern Ocean and plays an important role in the global carbon cycle. The key limiting factors controlling coccolithophore growth supporting this high PIC have not yet been well‐characterized in the remote Pacific sector, the lowest PIC but largest area of the GCB. Here, we present in situ physical and biogeochemical measurements along 150°W from January to February 2021, where a coccolithophore bloom occurred. In both months, PIC was elevated in the Subantarctic Zone (SAZ), where nitrate was >1 μM and temperatures were ∼13°C in January and ∼14°C in February, consistent with conditions previously associated with optimal coccolithophore growth potential. The highest PIC was associated with a relatively narrow temperature range that increased about 1°C between occupations. A fresher water mass had been transported to the 150°W meridian between occupations, and altimetry‐informed Lagrangian backtracking estimates show that most of this water was likely transported from the southeast within the SAZ. Applying the observations in a coccolithophore growth model for both January and February, we show that the ∼1.7°C increase in temperature can explain the rise in PIC between occupations. 

   more » « less
4. Global Trends in the Distribution of Biogenic Minerals in the Ocean

   https://doi.org/10.1029/2022JC019470  

   Subhas, Adam V.; Pavia, Frank J.; Dong, Sijia; Lam, Phoebe J. (February 2023, Journal of Geophysical Research: Oceans)

   Abstract The cycling of marine particulate matter is critical for sequestering carbon in the deep ocean and in marine sediments. Biogenic minerals such as calcium carbonate (CaCO₃) and opal add density to more buoyant organic material, facilitating particle sinking and export. Here, we compile and analyze a global data set of particulate organic carbon (POC), particulate inorganic carbon (PIC, or CaCO₃), and biogenic silica (bSi, or opal) concentrations collected using large volume pumps (LVPs). We analyze the distribution of all three biogenic phases in the small (1–53 μm) and large (>53 μm) size classes. Over the entire water column 76% of POC exists in the small size fraction. Similarly, the small size class contains 82% of PIC, indicating the importance of small‐sized coccolithophores to the PIC budget of the ocean. In contrast, 50% of bSi exists in the large size fraction, reflecting the larger size of diatoms and radiolarians compared with coccolithophores. We use PIC:POC and bSi:POC ratios in the upper ocean to document a consistent signal of shallow mineral dissolution, likely linked to biologically mediated processes. Sediment trap PIC:POC and bSi:POC are elevated with respect to LVP samples and increase strongly with depth, indicating the concentration of mineral phases and/or a deficit of POC in large sinking particles. We suggest that future sampling campaigns pair LVPs with sediment traps to capture the full particulate field, especially the large aggregates that contribute to mineral‐rich deep ocean fluxes, and may be missed by LVPs. 

   more » « less
5. Surface nitrogen conditions associated with bottle uptake measurements during a summer 2022 Alexandrium catenella bloom in the Alaskan Arctic (NRS2022_02S)

   https://doi.org/10.18739/A2X63B71H  

   Lim, Stephanie; Payne, Courtney; Arrigo, Kevin (January 2024, NSF Arctic Data Center)

   In the rapidly changing Arctic ecosystem, the recent emergence of harmful algal blooms (HABs) threatens human and ecosystem health. There is increasing evidence that toxic dinoflagellates of the Alexandrium genus are blooming in the Pacific Arctic Ocean, in dense enough concentrations to necessitate shellfishing closures and to detect toxins in marine mammals that forge in Alaskan waters. Our understanding of the nutrient dynamics that sustain HABs in the Pacific Arctic is severely limited, particularly as these blooms tend to occur in late summer when dissolved inorganic nitrogen is drawn down and limits phytoplankton growth. Dissolved organic nitrogen could prove a critical nitrogen source for HABs in the Pacific Arctic, as it has in other regions. This dataset presents measurements taken on Leg 2 of a research cruise (NRS2022_02S) on the Research Vessel (R/V) Norseman II in Aug-Sep 2022 to characterize the nutrient usage by A. catenella. It includes the nutrients (silicate, phosophate, total dissolved nitrogen, and four dissolved nitrogen substrates), particulate organic carbon and nitrogen, and chlorophyll concentrations associated with the beginning of 13 incubation experiments in which we measured nitrogen uptake rates by the surface biological community. We also include the salinity and temperature measurements from CTD-mounted sensors for water collection from Niskin bottles for each incubation set up. Other associated datasets include: Leah McRaven & Robert Pickart. (2024). Conductivity Temperature Depth (CTD) data from the Norseman II (NRS22-1s and NRS22-2s), as part of the 2022 Origin and Fate of Harmful Algal Blooms in the Warming Chukchi Sea cruise. Arctic Data Center. doi:10.18739/A2B853K56. Evangeline Fachon, Donald M Anderson, Mrunmayee Pathare, Michael Brosnahan, Eric Muhlbach, Kali Horn, Nathaniel Spada, & Anushka Rajagopalan. (2024). Alexandrium catenella planktonic cell abundance and toxicity from the Norseman II (NRS2022_01S and NRS2022_02S), as part of the 2022 Origin and Fate of Harmful Algal Blooms in the Warming Chukchi Sea cruise. Arctic Data Center. doi:10.18739/A2804XM7S. Miguel Goni & Dean Stockwell. (2024). Conductivity-Temperature-Depth (CTD) Bottle Data from the Norseman II cruises (NRS2022_01S and NRS2022_02S) including Particulate Organic Carbon (POC) Particulate Nitrogen (PN), Chlorophyll (Chl), Phaeophytin (Phaeo), and dissolved nutrients (Nitrate, Nitrite, Phosphate, Silicate, and Ammonium) (2022). Arctic Data Center. doi:10.18739/A2M90249T. 

   more » « less