Research ArticleOCEANOGRAPHY

Dynamic flows create potentially habitable conditions in Antarctic subglacial lakes

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Science Advances  17 Feb 2021:
Vol. 7, no. 8, eabc3972
DOI: 10.1126/sciadv.abc3972
  • Fig. 1 Problem schematic.

    We provide predictions about the characteristic velocity of the large-scale circulation Ulsc, the characteristic velocity of turbulent plumes U, the thickness δ of the top stable conductive layer, and the anomalous temperature of the well-mixed bulk Tbulk (i.e., in excess of the freezing temperature Tf). The problem parameters are the water depth h, the ice thickness H (or ice overburden pressure pi), the Coriolis frequency f (due to Earth’s rotation), and the geothermal flux F.

  • Fig. 2 Thermal expansion coefficient.

    Plot of the thermal expansion coefficient α as a function of (T, p) superimposed with profiles of the temperature of maximum density Td (red solid line) and freezing temperature Tf (black solid line) with pressure. For small pressures p < p*, with p* the critical inversion pressure (blue dashed line), Td > Tf such that there exists a range of temperatures Tf < T < Td for which α is negative (area appearing with red colors) and water masses become anomalously denser with increasing temperatures. For p < p* and T > Td, or pp*, the water becomes monotonically lighter as temperature increases, which is the typical behavior of most fluids.

  • Fig. 3 Critical heat flux.

    (A) Minimum heat flux required to trigger vertical convection in subglacial lakes as a function of lake depth (bottom axis) and ice overburden pressure (left axis) or ice thickness (right axis). Solid lines are isocontours in mW/m2 of required heat flux, while filled circles highlight the positions of five well-known lakes in parameter space (see legend to the right). (B) Ice thickness distribution of isolated subglacial lakes from the last published inventory (2). The dashed gray lines highlight the critical thickness H*.

  • Fig. 4 Conductive layer thickness and anomalous bulk temperature.

    (A and B) Thickness δ of the conductive stratified layer at the top of subglacial lakes assuming a geothermal flux of 50 mW/m2. (A) δ as a function of lake depth (bottom axis) and ice pressure (left axis). (B) δ as a function of ice pressure only for selected lake depths of 32, 156, and 1067 m [shown by vertical lines in (A)]. GL refers to results obtained with the GL theory and h = 1067 m. (C and D) Same as (A) and (B) but for the anomalous bulk temperature Tbulk (above Tf) of the well-mixed convective layer.

  • Fig. 5 Characteristic turbulent flow velocity and length scale.

    (A and C) Same as Fig. 4 (A and C), but for (A) the turbulent flow (plume) velocity U and (C) the characteristic length scale 𝓁 in the convective layer. (B and D) Turbulent flow velocity U and length scale 𝓁 as functions of lake depth only, for selected ice thicknesses H = 3945, 2653, and 1000 m [shown by horizontal lines in (A) and (C)]. GL refers to the GL predictions for the large-scale velocity Ulsc of vertical convection for H = 3945 m (shown by filled black squares). In (B), we also show a prediction for the horizontal velocity Vhc of the baroclinic flow along a tilted ice-water interface, assuming either a steep slope s = 10−2 (green stars) or a moderate slope s = 10−3 (tilted blue crosses).

  • Table 1 Properties and expected characteristics of five Antarctic subglacial lakes.

    The last column is the predicted maximum diameter of particulates maintained in suspension in the mixed bulk by the large-scale circulation of vertical convection (see Discussion section). Geophysical characteristics are obtained from (2, 9, 10, 16, 57, 58), while flow conditions are derived from scaling laws discussed in the Results section of the main text and described in detail in the sections, “Scaling laws for nonrotating vertical convection” and “Scaling laws for rotating horizontal convection,” in the Materials and Methods. Ice drop refers to the difference in ice thickness above the lake due to the mean slope of the ice-water interface.

    Ice
    thickness
    (m)
    Ice drop
    (m)
    Lake
    length
    (km)
    Water
    depth (m)
    δ (m)Tbulk (K)ℓ (m)U (mm/s)Ulsc
    (mm/s)
    Vhc
    (mm/s)
    2rmax
    (μm)
    CECs265315910.353007.70.691.60.970.320.04122
    SPL28573010324.70.420.80.100.040.0107.8
    Ellsworth3400300101560.0770.00691.20.690.260.06620
    Vostok394560028010670.0660.00592.33.800.850.06636
    Concordia4055168451260.0630.00561.00.830.310.04422

Supplementary Materials

  • Supplementary Materials

    Dynamic flows create potentially habitable conditions in Antarctic subglacial lakes

    Louis-Alexandre Couston and Martin Siegert

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