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Thermodynamics: Calculating Latent and Specific Heat, Example Problem latent heat of transformation

Research article 19 Apr Correspondence : Robert J. Allen rjallen ucr.

latent heat of transformation

By regulating the global transport of heat, freshwater, and carbon, the Atlantic meridional link circulation AMOC serves as an important component of the climate system. During the late 20th and early 21st centuries, indirect observations and models suggest a weakening of the AMOC. Direct AMOC observations also suggest a weakening during the early 21st century but with substantial interannual variability.

latent heat of transformation

Long-term weakening of the AMOC has been associated with increasing greenhouse gases GHGsbut some modeling studies suggest the build up of anthropogenic aerosols AAs may have offset part of the GHG-induced weakening. These multi-decadal AMOC variations are related to changes in North Atlantic atmospheric circulation, including an altered transfromation level pressure gradient, storm track activity, surface winds, and heat fluxes, which drive changes in the subpolar North Atlantic surface density flux. To further investigate these AMOC relationships, we perform a regression analysis and decompose these North Atlantic climate responses into an anthropogenic aerosol-forced component and a subsequent AMOC-related feedback.

Changes in natural forcings, latent heat of transformation solar variability and volcanic aerosols, yield negligible AMOC changes.

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More specifically, our results latent heat of transformation that AMOC multi-decadal variability is initiated by North Atlantic aerosol optical thickness click here to net surface shortwave radiation and sea surface temperature and hence sea surface densitywhich in turn affect sea level pressure gradient and surface wind and — via latent and sensible heat fluxes — sea surface density flux through its thermal component.

AMOC-related feedbacks act to reinforce this aerosol-forced AMOC response, largely due to changes in sea surface salinity and hence sea surface densitywith temperature-related and cloud-related feedbacks acting to mute the initial response. Although aspects of the CMIP6 all-forcing multi-model mean response resembles observations, notable differences exist. The CMIP6 multi-model mean also underestimates the observed increase in North Atlantic ocean heat content, and although the CMIP6 North Atlantic atmospheric circulation responses — particularly the overall patterns — are similar to observations, the simulated responses are weaker than those observed, implying they are only partially externally forced.

latent heat of transformation

The possible causes of these differences include internal climate variability, observational uncertainties, and model shortcomings, including excessive aerosol forcing. A handful of CMIP6 realizations yield AMOC evolution since oc to the indirect observations, implying the inferred AMOC weakening from to and even from to may have a significant contribution from internal i. Hassan, T. Author Cynthia A. The Atlantic meridional overturning circulation AMOC is an important component of the climate system, transporting large amounts of heat and freshwater poleward Talley; Buckley and Marshall The AMOC latent heat of transformation variability on a range of timescales, impacting not only surface temperature but also and sea level in several regions Delworth and Mann; Knight et al.

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The RAPID array shows a strong in the first part of the record and a slower increase afterwards. This record suggests an overall AMOC decline at a rate as high as 0. The causes of this recent AMOC slow-down remain highly debated and may be related to natural decadal variability Zhao and Johns; Jackson et al. However, longer-term evidence, including sea surface temperature fingerprints and coral-based latent heat of transformation, also suggest AMOC weakening — by about 0.

Although climate models this web page on the precise magnitude of the AMOC weakening — and differ substantially in their representation of the strength and depth of the AMOC — model simulations predict AMOC weakening in response to increasing greenhouse gases Gregory et al. This has been related to reduced ocean heat loss, and secondarily through increased freshwater input at high latitudes, both of which decrease the density of sea water in the subpolar North Atlantic i.

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Warming of the tropical Indian Ocean — by means of atmospheric teleconnections and changes in ocean salinity and circulation — may exert a stabilizing effect on the AMOC, attenuating its recent weakening Hu and Fedorov Overall, our understanding of how anthropogenic perturbations impact the AMOC remains limited. There is considerable debate on the role of anthropogenic aerosols in driving North Atlantic climate variability. One study argued anthropogenic aerosols are the dominant driver of Atlantic Multidecadal Variability a term encompassing Atlantic climate variabilityprimarily through aerosol—cloud interactions and modification of net surface shortwave radiation Booth et al.

Others have also suggested a role of anthropogenic forcing, including aerosols, in driving Atlantic Multidecadal Variability Evan et al. Menary et al. They argue that this is primarily driven by increased salinification of the North Atlantic subpolar gyre via increased evaporation, decreased flux of ice through the Fram Strait, and increased salt advection from the subtropical Atlantic. This study, like many of the earlier studies, relies on a single climate model. Very recently, latent heat of transformation, Menary et al. Furthermore, Ma et al.]

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