scholarly journals Spatiotemporal Variations in Surface Heat Loss Imply a Heterogeneous Mantle Cooling History

2021 ◽  
Vol 48 (6) ◽  
Author(s):  
Krister S. Karlsen ◽  
Clinton P. Conrad ◽  
Mathew Domeier ◽  
Reidar G. Trønnes
Keyword(s):  
Heat Loss ◽  
Surface Heat ◽  
Spatiotemporal Variations ◽  
Cooling History ◽  
Heterogeneous Mantle

scholarly journals Meridional Overturning Circulations Driven by Surface Wind and Buoyancy Forcing

2015 ◽  
Vol 45 (11) ◽  
pp. 2701-2714 ◽  
Author(s):  
Michael J. Bell
Keyword(s):  
Heat Loss ◽  
Water Mass ◽  
Surface Wind ◽  
Surface Heat ◽  
Meridional Overturning Circulation ◽  
Western Boundary ◽  
Eastern Boundary ◽  
Transformation Rates ◽  
Meridional Overturning ◽  
Water Mass Transformations

AbstractThe meridional overturning circulation (MOC) can be considered to consist of a downwelling limb in the Northern Hemisphere (NH) and an upwelling limb in the Southern Hemisphere (SH) that are connected via western boundary currents. Steady-state analytical gyre-scale solutions of the planetary geostrophic equations are derived for a downwelling limb driven in the NH solely by surface heat loss. In these solutions the rates of the water mass transformations between layers driven by the surface heat loss determine the strength of the downwelling limb. Simple expressions are obtained for these transformation rates that depend on the most southerly latitudes where heat loss occurs and the depths of the isopycnals on the eastern boundary. Previously derived expressions for the water mass transformation rates in subpolar gyres driven by the Ekman upwelling characteristic of the SH are also summarized. Explicit expressions for the MOC transport and the depths of isopycnals on the eastern boundary are then derived by equating the water mass transformations in the upwelling and downwelling limbs. The MOC obtained for a “single-basin” two-layer model is shown to be generally consistent with that obtained by Gnanadesikan. The model’s energetics are derived and discussed. In a world without a circumpolar channel in the SH, it is suggested that the upwelling limb would feed downwelling limbs in both hemispheres. In a world with two basins in the NH, if one of them has a strong halocline the model suggests that the MOC would be very weak in that basin.

Facile measurement of surface heat loss from polymer thin films via fluorescence thermometry

2017 ◽  
Vol 56 (8) ◽  
pp. 643-652 ◽  
Author(s):  
Gabriel Firestone ◽  
Jason R. Bochinski ◽  
Jeffrey S. Meth ◽  
Laura I. Clarke
Keyword(s):  
Thin Films ◽  
Heat Loss ◽  
Polymer Thin Films ◽  
Surface Heat ◽  
Fluorescence Thermometry

How does heat flux affect potential vorticity in the Southern Ocean?

2021 ◽  
Author(s):  
Ciara Pimm ◽  
Ric Williams ◽  
Dan Jones ◽  
Andrew Meijers
Keyword(s):  
Southern Ocean ◽  
Heat Loss ◽  
Ocean Circulation ◽  
Potential Vorticity ◽  
Potential Temperature ◽  
Surface Heat ◽  
Global Ocean ◽  
Adjoint Sensitivity ◽  
Mode Water ◽  
Physical Insight

<p>Surface heat loss leads to thick winter mixed layers over the Southern Ocean, which feeds the formation of subsurface mode water pools through subduction. One such water class is Subantarctic Mode Water (SAMW), which is characterised by its low absolute potential vorticity. SAMW occurs in several regions of the Southern Ocean on the northern side of the Antarctic circumpolar current and it extends into the subtropics below the surface on different density surfaces. Using the ECCOv4 global ocean circulation model, we conduct a series of adjoint sensitivity experiments and forward perturbation experiments at key Southern Ocean SAMW formation sites, focusing on how different surface forcing affects potential vorticity. This adjoint approach produces time-evolving sensitivity maps that identify where and when surface heat loss potentially impacts the formation of mode waters. Over the first year in lead time, we find that greater surface heat loss leads to stronger convection and lower SAMW potential vorticity. On lead times longer than one year, in some regions of high sensitivity, the sensitivity reverses its sign, such that more surface heat loss ultimately leads to higher values of potential vorticity in the subduction regions. This reversal of sign of the sensitivity can be attributed to a shift from local convective forcing to upstream advective forcing and the associated redistribution of potential temperature and salinity. Surface adjustment also plays a role in the upstream sensitivities due to the tendency for temperature anomalies to be weakened through compensating salinity before reaching the subduction zone. We use the adjoint sensitivity fields to design a set of forward, non-linear perturbation experiments to provide physical insight into how ventilation affects the uptake of heat and carbon. This physical insight is important for identifying which physical mechanisms affect the subducted properties in the Southern Ocean, especially as the ocean warms through climate change.</p>

How does aerosol forcing drive a strengthening of the AMOC in CMIP6 historical simulations?

2021 ◽  
Author(s):  
Jon Robson ◽  
Matthew Menary ◽  
Jonathan Gregory ◽  
Colin Jones ◽  
Bablu Sinha ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Loss ◽  
North Atlantic ◽  
Surface Heat ◽  
Meridional Overturning Circulation ◽  
Radiation Budget ◽  
Anthropogenic Aerosols ◽  
The North ◽  
Aerosol Forcing ◽  
The North Atlantic

<p>Previous work has shown that anthropogenic aerosol emissions drive a strengthening in the Atlantic Meridional Overturning Circulation (AMOC) in CMIP6 historical simulations over ~1850-1985. However, the mechanisms driving the increase are not fully understood. Previously, forced AMOC changes have been linked to changes in surface heat fluxes, changes in salinity, and interhemispheric energy imbalances. Here we will show that across CMIP6 historical simulations there is a strong correlation between ocean heat loss from the subpolar North Atlantic and the forced change in the AMOC. Furthermore, the model spread in the surface heat flux change explains the spread of the AMOC response and is correlated with the strength of the models’ aerosol forcing.  However, the AMOC change is not strongly related to changes in downwelling surface shortwave radiation over the North Atlantic, showing that anthropogenic aerosols do not drive AMOC change through changes in the local surface radiation budget. Rather, by separating the models into those with ‘strong’ and ‘weak’ aerosol forcing, we show that aerosols appear to predominantly imprint their impact on the AMOC through changes in surface air temperature over the Northern Hemisphere and the consequent impact on latent and sensible heat flux. This thermodynamic driver (i.e. more heat loss from the North Atlantic) is enhanced both by the increase in the AMOC itself, which acts as a positive feedback, and by a response in atmospheric circulation. </p>

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