Grabon Jeffrey S.

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Grabon
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Jeffrey S.
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  • Thesis
    An analysis of Atlantic Water in the Arctic Ocean using the Arctic Subpolar Gyre State Estimate and observations
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2020-09) Grabon, Jeffrey S. ; Toole, John M.
    The Atlantic Water (AW) Layer in the Arctic Subpolar gyre sTate Estimate (ASTE), a regional, medium-resolution coupled ocean-sea ice state estimate, is analyzed for the first time using bounding isopycnals. A surge of AW, marked by rapid increases in mean AW Layer potential temperature and AW Layer thickness, begins two years into the state estimate (2004) and traverses the Arctic Ocean along boundary current pathways at approximately 2 cm/s. The surge also alters AW flow direction and speed including a significant reversal in flow direction along the Lomonosov Ridge. The surge results in a new quasi-steady AW flow from 2010 through the end of the state estimate period in 2017. The time-mean AW circulation during this time period indicates a significant amount of AW spreads over the Lomonosov Ridge rather than directly returning along the ridge to Fram Strait. A three-layer depiction of ASTE’s overturning circulation within the AO indicates AW is converted to colder, fresher Surface Layer water at a faster rate than is transformed to Bottom Water (1.2 Sv vs. 0.4 Sv). Observed AW properties compared to ASTE output indicate increasing misfit during the simulated period with ASTE’s AW Layer generally being warmer and thicker than in observations.
  • Article
    An analysis of Atlantic water in the Arctic Ocean using the Arctic subpolar gyre state estimate and observations
    (Elsevier, 2021-09-13) Grabon, Jeffrey S. ; Toole, John M. ; Nguyen, An T. ; Krishfield, Richard A.
    The Atlantic Water (AW) Layer in the Arctic Subpolar gyre sTate Estimate Release 1 (ASTE R1), a data-constrained, regional, medium-resolution coupled ocean-sea ice model, is analyzed for the period 2004–2017 in combination with available hydrographic data. The study, focusing on AW defined as the waters between two bounding isopycnals, examines the time-average, mean seasonal cycle and interannual variability of AW Layer properties and circulation. A surge of AW, marked by rapid increases in mean AW Layer potential temperature and AW Layer thickness, begins two years into the state estimate and traverses the Arctic Ocean along boundary current pathways at a speed of 1–2 cm/s. The surge also alters AW circulation, including a reversal in flow direction along the Lomonosov Ridge, resulting in a new quasi-steady AW circulation from 2010 through the end of the state estimate period. The time-mean AW circulation during this latter time period indicates that a significant amount of AW spreads over the Lomonosov Ridge rather than directly returning along the ridge to Fram Strait. A three-layer depiction of the time-averaged ASTE R1 overturning circulation within the Arctic Ocean reveals that more AW is converted to colder, fresher Surface Layer water than is transformed to Deep and Bottom Water (1.2 Sv vs. 0.4 Sv). ASTE R1 also exhibits an increase in the volume of AW over the study period at a rate of 1.4 Sv, with near compensating decrease in Deep and Bottom Water volume. Observed AW properties compared to ASTE R1 output reveal increasing misfit during the simulated period with the ASTE R1 AW Layer generally being warmer and thicker than in observations.