Bam Wokil

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Last Name
Bam
First Name
Wokil
ORCID
0000-0002-7320-3496

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  • Article
    Climate change impacts to the Arctic Ocean revealed from high resolution GEOTRACES Po-210-Pb-210-Ra-226 disequilibria studies
    (American Geophysical Union, 2022-04-06) Baskaran, Mark ; Krupp, Katherine ; Bam, Wokil ; Maiti, Kanchan
    Climate change is transforming the Arctic Ocean in unprecedented ways which can be most directly observed in the systematic decline in seasonal ice coverage. From the collection and analysis of particulate and dissolved activities of 210Po and 210Pb from four deepwater superstations, as a part of the US Arctic GEOTRACES cruise during 2015, and in conjunction with previously published data, the temporal and spatial variations in their activities, inventories and residence times are evaluated. The results show that the partitioning of particulate and dissolved phases has changed significantly in the 8 years between 2007 and 2015, while the total 210Po and 210Pb activities have remained relatively unchanged. Observed total 210Po/210Pb activity ratio was less than unity in all deepwater stations, implying disequilibria in the entire water column. From the distribution of total 210Po and 210Pb in the upper 500 m of all major Arctic Basins, the derived scavenging efficiencies decrease as per the following sequence: Makarov Basin > Gakkel Bridge > Canada Basin Nansen Basin ∼ Amundsen Basin > Alpha Ridge, which is the reverse order of the calculated residence times of 210PoT. The scavenging intensities differ between the fully ice-covered, partially ice-covered, and no ice-covered stations, as observed from the differences in the average activities of 210Po and 210Pb. The average settling velocity of particulate matter based on the 210Pb activity is similar to the published values based on 230Th, indicating removal mechanism(s) of Th and Pb is (are) similar.
  • Dataset
    Small particulate Polonium 210 and Lead 210 measurements from the Western Arctic Ocean, which were sampled as part of the 2015 US GEOTRACES Cruise, HLY1502 (GN01), on USCGC Healy
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2020-04-13) Maiti, Kanchan ; Bam, Wokil
    This dataset includes small particulate Polonium 210 and Lead 210 measurements from the Western Arctic Ocean, which were sampled as part of the 2015 US GEOTRACES Cruise (GN01; HLY1502). These data have been published in Bam et al., 2020. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/808502
  • Dataset
    Dissolved and large particulate Polonium 210 and Lead 210 measurements from the Western Arctic Ocean, which were sampled as part of the 2015 US GEOTRACES Cruise, HLY1502 (GN01), on USCGC Healy
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2020-04-13) Maiti, Kanchan ; Bam, Wokil
    This dataset includes dissolved and large particulate Polonium 210 and Lead 210 measurements from the Western Arctic Ocean, which were sampled as part of the 2015 US GEOTRACES Cruise (GN01; HLY1502). These data have been published in Bam et al., 2020. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/808151
  • Article
    Exploring new frontiers in marine radioisotope tracing - adapting to new opportunities and challenges
    (Frontiers Media, 2020-06-03) Cresswell, Tom ; Metian, Marc ; Fisher, Nicholas S. ; Charmasson, Sabine ; Hansman, Roberta L. ; Bam, Wokil ; Bock, Christian ; Swarzenski, Peter W.
    Radioisotopes have been used in earth and environmental sciences for over 150 years and provide unique tools to study environmental processes in great detail from a cellular level through to an oceanic basin scale. These nuclear techniques have been employed to understand coastal and marine ecosystems via laboratory and field studies in terms of how aquatic organisms respond to environmental stressors, including temperature, pH, nutrients, metals, organic anthropogenic contaminants, and biological toxins. Global marine issues, such as ocean warming, deoxygenation, plastic pollution, ocean acidification, increased duration, and intensity of toxic harmful algal blooms (HABs), and coastal contamination are all impacting marine environments, thereby imposing various environmental and economic risks. Being able to reliably assess the condition of coastal and marine ecosystems, and how they may respond to future disturbances, can provide vital information for society in the sustainable management of their marine environments. This paper summarizes the historical use of radiotracers in these systems, describes how existing techniques of radioecological tracing can be developed for specific current environmental issues and provides information on emerging issues that would benefit from current and new radiotracer methods. Current challenges with using radioecological tracers and opportunities are highlighted, as well as opportunities to maximize the application of these methods to greatly increase the ability of environmental managers to conduct evidence-based management of coastal and marine ecosystems.
  • Article
    Carbon and silica fluxes during a declining North Atlantic spring bloom as part of the EXPORTS program
    (Elsevier, 2023-12-12) Clevenger, Samantha J. ; Benitez-Nelson, Claudia R. ; Roca-Marti, Montserrat ; Bam, Wokil ; Estapa, Margaret L. ; Kenyon, Jennifer A. ; Pike, Steven M. ; Resplandy, Laure ; Wyatt, Abigale M. ; Buesseler, Ken O.
    The goal of NASA's EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) project is to develop a predictive understanding of the fate of global ocean primary productivity and export of carbon from the surface to the deep ocean. Thorium-234 (234Th, t1/2 = 24.1 d) was used to measure sinking particle export from an anticyclonic eddy during the EXPORTS North Atlantic cruise (May 2021) at the Porcupine Abyssal Plain. The four-week sampling period was broken into three time periods (“epochs”) where 800 234Th seawater samples were collected from over 50 CTD casts with high depth resolution over the upper 500 m. Size-fractioned particulate samples were collected to determine particulate organic carbon (POC) and biogenic silica (bSi) to 234Th ratios using in situ McLane pumps. A 234Th non-steady state model shows an eddy center epoch average progression of increasing 234Th export (∼2800 ± 300 (Epoch 1; standard deviation) to 4500 ± 700 (Epoch 3) dpm m−2 d−1) out of the top 110 m of the water column over the course of the cruise (29 d). This translates into an epoch average progression of ∼11 ± 1 to 14 ± 2 mmol C m−2 d−1 of sinking POC flux, and ∼ 3 ± 1 to 6 ± 1 mmol bSi m−2 d−1 of sinking bSi flux to deeper waters at 110 m. The overall efficiency of the biological carbon pump (amount of net primary production reaching 100 m below the euphotic zone) increases from ∼10% to ∼30% throughout the sampling period. The temporal trends discussed extensively in this paper show that POC and bSi export increase during diatom bloom evolution.