Thermal Weakening, Convergent Flow, and Vertical Heat Transport in the Northeast Greenland Ice Stream Shear Margins

2019 ◽  
Vol 46 (14) ◽  
pp. 8184-8193 ◽  
Author(s):  
N. Holschuh ◽  
D. A. Lilien ◽  
K. Christianson
Keyword(s):  
Heat Transport ◽  
Ice Stream ◽  
Vertical Heat ◽  
Convergent Flow

scholarly journals Vertical heat transport in eddying ocean models

2008 ◽  
Vol 35 (23) ◽  
Author(s):  
C. L. Wolfe ◽  
P. Cessi ◽  
J. L. McClean ◽  
M. E. Maltrud
Keyword(s):  
Heat Transport ◽  
Vertical Heat ◽  
Ocean Models

A bound on the vertical transport of heat in the ‘ultimate’ state of slippery convection at large Prandtl numbers

2013 ◽  
Vol 729 ◽  
pp. 103-122 ◽  
Author(s):  
Xiaoming Wang ◽  
Jared P. Whitehead
Keyword(s):  
Quadratic Form ◽  
Boundary Conditions ◽  
Heat Transport ◽  
Upper Bound ◽  
Vertical Transport ◽  
Three Dimensions ◽  
Free Boundaries ◽  
Ultimate State ◽  
Vertical Heat ◽  
Prandtl Numbers

AbstractAn upper bound on the rate of vertical heat transport is established in three dimensions for stress-free velocity boundary conditions on horizontally periodic plates. A variation of the background method is implemented that allows negative values of the quadratic form to yield ‘small’ ($O\left(1/ \mathit{Pr}\right)$) corrections to the subsequent bound. For large (but finite) Prandtl numbers this bound is an improvement over the ‘ultimate’$R{a}^{1/ 2} $scaling and, in the limit of infinite$Pr$, agrees with the bound of$R{a}^{5/ 12} $recently derived in that limit for stress-free boundaries.

scholarly journals Vertical Redistribution of Oceanic Heat Content

2015 ◽  
Vol 28 (9) ◽  
pp. 3821-3833 ◽  
Author(s):  
Xinfeng Liang ◽  
Carl Wunsch ◽  
Patrick Heimbach ◽  
Gael Forget
Keyword(s):  
Heat Flux ◽  
Heat Exchange ◽  
Heat Transport ◽  
Heat Content ◽  
Deep Ocean ◽  
Temporal Variations ◽  
Near Surface ◽  
Carbon 14 ◽  
Vertical Heat ◽  
Vertical Heat Flux

Abstract Estimated values of recent oceanic heat uptake are on the order of a few tenths of a W m−2, and are a very small residual of air–sea exchanges, with annual average regional magnitudes of hundreds of W m−2. Using a dynamically consistent state estimate, the redistribution of heat within the ocean is calculated over a 20-yr period. The 20-yr mean vertical heat flux shows strong variations in both the lateral and vertical directions, consistent with the ocean being a dynamically active and spatially complex heat exchanger. Between mixing and advection, the two processes determining the vertical heat transport in the deep ocean, advection plays a more important role in setting the spatial patterns of vertical heat exchange and its temporal variations. The global integral of vertical heat flux shows an upward heat transport in the deep ocean, suggesting a cooling trend in the deep ocean. These results support an inference that the near-surface thermal properties of the ocean are a consequence, at least in part, of internal redistributions of heat, some of which must reflect water that has undergone long trajectories since last exposure to the atmosphere. The small residual heat exchange with the atmosphere today is unlikely to represent the interaction with an ocean that was in thermal equilibrium at the start of global warming. An analogy is drawn with carbon-14 “reservoir ages,” which range from over hundreds to a thousand years.

scholarly journals MEP solution for a minimal climate model: success and limitation of a variational problem

2011 ◽  
Vol 2 (1) ◽  
pp. 393-434
Author(s):  
S. Pascale ◽  
J. M. Gregory ◽  
M. H. P. Ambaum ◽  
R. Tailleux ◽  
V. Lucarini
Keyword(s):  
Entropy Production ◽  
Heat Transport ◽  
Large Scale ◽  
Climate Model ◽  
Longwave Radiation ◽  
Critical Discussion ◽  
Heat Fluxes ◽  
Box Model ◽  
Temperature Fields ◽  
Vertical Heat

Abstract. Maximum Entropy Production conjecture (MEP) is applied to a minimal four-box model of climate which accounts for both horizontal and vertical material heat fluxes. It is shown that, under condition of fixed insolation, a MEP solution is found with reasonably realistic temperature and heat fluxes, thus generalising results from independent two-box horizontal or vertical models. It is also shown that the meridional and the vertical entropy production terms are independently involved in the maximisation and thus MEP can be applied to each subsystem with fixed boundary conditions. We then extend the four-box model by increasing its number of degrees of freedom, and test its realism by comparing it with a GCM output. An order-of-magnitude evaluation of contributions to the material entropy production (≈50 mW m−2 K−1) due to horizontal and vertical processes within the climate system is carried out by using ad hoc temperature fields. It turns out that approximately 40 mW m−2 K−1 is the entropy production due to vertical heat transport and 5–7 mW m−2 K−1 to horizontal heat transport. A MEP solution is found which is fairly realistic as far as the horizontal large scale organisation of the surface climate is concerned whereas the vertical structure looks to be unrealistic and presents seriously unstable features. Finally a more general problem is investigated in which the longwave transmissivity is varied simultaneously with the temperature. This leads to a MEP solution characterised by a much warmer climate, with very vigorous vertical heat fluxes, in which the atmosphere is opaque to longwave radiation. A critical discussion about how to interpret MEP and how to apply it in a physically correct way concludes the paper.

scholarly journals Change of the Global Ocean Vertical Heat Transport over 1993–2010

2017 ◽  
Vol 30 (14) ◽  
pp. 5319-5327 ◽  
Author(s):  
Xinfeng Liang ◽  
Christopher G. Piecuch ◽  
Rui M. Ponte ◽  
Gael Forget ◽  
Carl Wunsch ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Exchange ◽  
Heat Transport ◽  
Heat Content ◽  
Ocean Heat Content ◽  
Global Ocean ◽  
Mixing Processes ◽  
State Estimate ◽  
Vertical Heat ◽  
Vertical Heat Flux

A dynamically and data-consistent ocean state estimate during 1993–2010 is analyzed for bidecadal changes in the mechanisms of heat exchange between the upper and lower oceans. Many patterns of change are consistent with prior studies. However, at various levels above 1800 m the global integral of the change in ocean vertical heat flux involves the summation of positive and negative regional contributions and is not statistically significant. The nonsignificance of change in the global ocean vertical heat transport from an ocean state estimate that provides global coverage and regular sampling, spatially and temporally, raises the question of whether an adequate observational database exists to assess changes in the upper ocean heat content over the past few decades. Also, whereas the advective term largely determines the spatial pattern of the change in ocean vertical heat flux, its global integral is not significantly different from zero. In contrast, the diffusive term, although regionally weak except in high-latitude oceans, produces a statistically significant extra downward heat flux during the 2000s. This result suggests that besides ocean advection, ocean mixing processes, including isopycnal and diapycnal as well as convective mixing, are important for the decadal variation of the heat exchange between upper and deep oceans as well. Furthermore, the analyses herein indicate that focusing on any particular region in explaining changes of the global ocean heat content is misleading.

Vertical Heat Fluxes beneath Idealized Sea Ice Leads in Large-Eddy Simulations: Comparison with Observations from the SHEBA Experiment

2020 ◽  
Vol 50 (8) ◽  
pp. 2189-2202
Author(s):  
Pascal Bourgault ◽  
David Straub ◽  
Kevin Duquette ◽  
Louis-Philippe Nadeau ◽  
Bruno Tremblay
Keyword(s):  
Sea Ice ◽  
Heat Transport ◽  
Heat Fluxes ◽  
Large Eddy Simulations ◽  
The Arctic ◽  
Turbulent Heat ◽  
Buoyancy Forcing ◽  
Large Eddy ◽  
Vertical Heat ◽  
Ice Leads

AbstractLarge-eddy simulations (Δx = Δz = 1 m) are used to examine vertical ocean heat fluxes driven by mechanical and buoyancy forcing across idealized sea ice leads. Forcing parameters approximate conditions from a shear event during the Surface Heat Budget of the Arctic (SHEBA) experiment in March 1998. In situ measurements near the lead showed isopycnal displacements of 14 m and turbulent vertical heat fluxes up to 400 W m−2, both of which were attributed to a strong cyclonic stress curl localized along the lead axis. By contrast, the large-eddy simulations show cyclonic shear across the lead to produce no turbulence, with vertical heat transport instead related to an overturning cell that connects a broad upwelling near the lead to downwelling farther away. Anticyclonic forcing produces an opposite-signed overturning cell, but with an intense, narrow downwelling jet and strong turbulent heat fluxes (~100 W m−2) near the lead. For both signs of curl, domain-integrated heat transport due to the overturning cells is somewhat larger than the turbulent heat flux, the latter being confined to the vicinity of the lead. Buoyancy forcing related to sea ice formation in the lead was found to increase both the turbulent and the cell-related heat fluxes (by up to 50% and 10%, respectively). Vertical isopycnal displacements for the upwelling case were found to increase linearly with the strength of the forcing. Possible reasons for the discrepancies with the observations include finer scale variation in the surface ocean stress and turbulence associated with the formation of a ridge during the shear event.

scholarly journals Dynamical Heat-Flux Feedbacks and Global Climate Stability

1984 ◽  
Vol 5 ◽  
pp. 106-110 ◽  
Author(s):  
Gyula Molnar ◽  
Wei-Chyung Wang
Keyword(s):  
Heat Flux ◽  
Global Stability ◽  
Heat Transport ◽  
Global Climate ◽  
Dynamical Model ◽  
Meridional Heat Transport ◽  
Low Latitude ◽  
Climate Stability ◽  
Vertical Heat ◽  
The Face

In the face of the faint young sun-climate paradox, the plausible effects of dynamical heat-flux feedbacks on global stability were examined using a coupled high- and low-latitude radiative-dynamical model. The global stability is found to depend very strongly on the vertical heat transport, which is also closely coupled to the meridional heat transport. This coupling and the associated dynamical heat-flux feedbacks, treated within the framework of the radiative-dynamical model, was found to produce a fairly strong negative feedback. Our results indicate that the dynamical heat-flux feedbacks inherent in the climate system may potentially enhance the global stability.

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