Research ArticleEARTH SCIENCES

The frequency and extent of sub-ice phytoplankton blooms in the Arctic Ocean

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Science Advances  29 Mar 2017:
Vol. 3, no. 3, e1601191
DOI: 10.1126/sciadv.1601191
  • Fig. 1 Example seasonal cycles of climate variables, timing of sub-ice blooms, and model sensitivity.

    (A to D) Example time series of ocean mixed layer depth (A), sea ice thickness (B), surface downwelling solar irradiance (C), and melt pond fraction (D). Blue and red curves in (A) are deviations of ±8 m from the reference mixed layer depth curve. Blue and red curves in (B) are deviations in ice thickness of ±40 cm from the reference ice thickness curve. Green shaded line segments of the black curves in (A) to (D) indicate a sub-ice bloom is permitted. Green dots and gray boxes correspond to the average observed values and reported ranges observed during the 2011 bloom (4). (E and F) Sensitivity of bloom timing to perturbations in the reference seasonal cycle shown in (A) to (D). (E) The critical melt pond fraction φc calculated using the seasonal cycles of ocean mixed layer depth displayed in (A) (black solid, red dash-dot, and dashed blue curves). Gray curve is the seasonal cycle of melt pond fraction shown in (D). When curves of φc are lower than the dashed curves, a light-limited bloom would be permitted in that region. (F) Same as (E) but for the ice thickness seasonal cycles shown in (B).

  • Fig. 2 Spatial map of the average number of days of sufficient light for sub-ice phytoplankton blooms over time.

    (A to C) Shading indicates the number of days in May, from 1986 to 1995 (A), 1996 to 2005 (B), and 2006 to 2015 (C), where a sub-ice bloom is permitted. (D to F) Same as (A) to (C) but for June. (G to I) Same as (A) to (C) but for July. Red boxes in (D) to (F) indicate the region of the 2011 cruise. Baffin Bay and regions with an ice concentration less than 80% at every point during each time period are colored blue. Continents are colored gray.

  • Fig. 3 Evolution and variability of the pan-Arctic likelihood of sub-ice blooms over time.

    (A to C) Percentage by area of the Arctic Ocean that has greater than 80% ice concentration and permits growth for at least three consecutive days in May (A), June (B), and July (C). Red dashed lines are linear fits to the data.

  • Table 1 Analysis of the causes of changes in sub-ice blooms in the Arctic Ocean.

    The average fraction of the Arctic Ocean that permits a light-limited sub-ice bloom from 2006 to 2015 when labeled external fields are held constant at their mean 1986–1995 values. The Arctic is defined as the region with latitudes greater than 70°N, excluding Baffin Bay. Percentage by area refers to the average area of the Arctic with an ice concentration greater than 80%, in which at least three consecutive days permit enough light for a light-limited bloom to occur, averaged over the time period 2006–2015. The notation “x fixed” refers to output when the variable x is fixed at its mean 1986–1996 values. Variables that may be fixed are the ice thickness h, melt pond fraction φ, and ice concentration c. The final row is the average fraction of the Arctic Ocean that permits a light-limited sub-ice bloom from 2006 to 2015 when the melt pond fraction φ is is always equal to zero.

    May % areaJune % areaJuly % area
    None fixed1.1%13.1%21.4%
    h fixed0.3%1.5%2.2%
    φ fixed3.5%7.9%16.2%
    c fixed2.1%16.0 %31.1%
    h, c fixed0.3%1.1%2.0%
    φ, c fixed5.5%11.6%29.5%
    φ, h fixed0.9%1.4 %1.6%
    φ = 00.8%4.4%6.1%

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/3/e1601191/DC1

    text S1. Sensitivity to extinction coefficient in ice.

    text S2. Evolution of fields over time.

    text S3. Sensitivity analysis: Bounds on the area that permits sub-ice blooms.

    fig. S1. Sensitivity of bloom-permitting area to ice extinction coefficient.

    fig. S2. Evolution of ice concentration, melt pond fraction, and ice thickness over time.

    table S1. Ranges of the percentage of the Arctic Ocean (>70°N, excluding Baffin Bay) in which sub-ice blooms can occur, when sea ice thickness data are increased or decreased by 1 SD (for details on how this is computed, see text S2).

    table S2. Ranges of the percentage of the Arctic Ocean (>70°N, excluding Baffin Bay) in which sub-ice blooms can occur, when the melt pond coverage data are increased or decreased by 1 SD (for details on how this is computed, see text S2).

  • Supplementary Materials

    This PDF file includes:

    • text S1. Sensitivity to extinction coefficient in ice.
    • text S2. Evolution of fields over time.
    • text S3. Sensitivity analysis: Bounds on the area that permits sub-ice blooms.
    • fig. S1. Sensitivity of bloom-permitting area to ice extinction coefficient.
    • fig. S2. Evolution of ice concentration, melt pond fraction, and ice thickness over time.
    • table S1. Ranges of the percentage of the Arctic Ocean (>70°N, excluding Baffin Bay) in which sub-ice blooms can occur, when sea ice thickness data are increased or decreased by 1 SD (for details on how this is computed, see text S2).
    • table S2. Ranges of the percentage of the Arctic Ocean (>70°N, excluding Baffin Bay) in which sub-ice blooms can occur, when the melt pond coverage data are increased or decreased by 1 SD (for details on how this is computed, see text S2).

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