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Abstract A 15‐year (2004–2018) record of mooring observations from the upper 50 m of the ocean in the eastern Eurasian Basin reveals increased current speeds and vertical shear, associated with an increasing coupling between wind, ice, and the upper ocean over 2004–2018, particularly in summer. Substantial increases in current speeds and shears in the upper 50 m are dominated by a two times amplification of currents in the semidiurnal band, which includes tides and wind‐forced near‐inertial oscillations. For the first time the strengthened upper ocean currents and shear are observed to coincide with weakening stratification. This coupling links the Atlantic Water heat to the sea ice, a consequence of which would be reducing regional sea ice volume. These results point to a new positive feedback mechanism in which reduced sea ice extent facilitates more energetic inertial oscillations and associated upper‐ocean shear, thus leading to enhanced ventilation of the Atlantic Water.
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Estimating the Maximum Vertical Velocity at the Leading Edge of a Density Current
Abstract The maximum upward vertical velocity at the leading edge of a density current is commonly <10 m s−1. Studies of the vertical velocity, however, are relatively few, in part owing to the dearth of high-spatiotemporal-resolution observations. During the Plains Elevated Convection At Night (PECAN) field project, a mobile Doppler lidar measured a maximum vertical velocity of 13 m s−1 at the leading edge of a density current created by a mesoscale convective system during the night of 15 July 2015. Two other vertically pointing instruments recorded 8 m s−1 vertical velocities at the leading edge of the density current on the same night. This study describes the structure of the density current and attempts to estimate the maximum vertical velocity at their leading edges using the following properties: the density current depth, the slope of its head, and its perturbation potential temperature. The method is then be applied to estimate the maximum vertical velocity at the leading edge of density currents using idealized numerical simulations conducted in neutral and stable atmospheres with resting base states and in neutral and stable atmospheres with vertical wind shear. After testing this method on idealized simulations, this method is then used to estimate the vertical velocity at the leading edge of density currents documented in several previous studies. It was found that the maximum vertical velocity can be estimated to within 10%–15% of the observed or simulated maximum vertical velocity and indirectly accounts for parameters including environmental wind shear and static stability.
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- Award ID(s):
- 1947146
- PAR ID:
- 10199478
- Date Published:
- Journal Name:
- Journal of the Atmospheric Sciences
- Volume:
- 77
- Issue:
- 11
- ISSN:
- 0022-4928
- Page Range / eLocation ID:
- 3683 to 3700
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1175/JAS-D-20-0028.1
