The influence download feedbacks on equatorial atlantic variability

Influence of the meridional overturning circulation on. Remote influence of interdecadal pacific oscillation on the south atlantic meridional overturning circulation variability 2017 us amoc science team meeting may 24th, 2017 presenter. The influence of cloud feedbacks on equatorial atlantic variability. Effect of ocean mesoscale variability on the mean state of tropical atlantic climate hyodae seo,1 markus jochum,2 raghu murtugudde,3 and arthur j. We use the coarseresolution echam6 echam6cr with t31 horizontal grid 3. In boreal spring when the equatorial atlantic is uniformly warm, anomalies of crossequatorial sst gradient and the itcz are closely coupled, resulting in anomalous rainfall over northeastern brazil. The impact of mean state errors on equatorial atlantic. A warm indian ocean can produce atmospheric kelvin waves that propagate eastward and increase equatorial. However, from observations alone, it is not possible to quantify the influence of regional cloud feedbacks on equatorial climate variability. Upper equatorial atlantic variability during 2002 and 2005. Decadetocenturyscale climate variability and change. Interannual variability in the southern and equatorial atlantic is investigated using an atmospheric general circulation model agcm coupled to a slab ocean model som in the atlantic in order to isolate features of airsea interactions particular to this basin. Early 20thcentury arctic warming intensified by pacific. Shenfu dong2, sangki lee2 and edmo campos1,3 1cooperative institute for marine and atmospheric studies, university of miami, miami.

This paper explores climate variability of the lower troposphere and boundary layer in the tropical atlantic sector through a series of modeling simulations with a diagnostic primitive equation model. The influence of cloud feedbacks on equatorial atlantic variability article pdf available in journal of climate 287. Weakening of the equatorial atlantic cold tongue over the past six. South atlantic variability arising from airsea coupling. The north atlantic oscillation is the dominant mode of atmospheric variability in the north atlantic sector. The climate in the tropical atlantic ta shows significant seasonal to decadal and longer variability see e. Impacts of the atlantic equatorial mode in a warmer climate. Potential feedbacks between pacific ocean ecosystems.

Here, using observations and model experiments, we show that the. Climate can be loosely defined as the ensemble of weather. Part of the oceans response is local and rapid surface temperature, mixed layer depth, upper ocean heat content, surface ekman. The simulation of equatorial atlantic variability deserves more. Influence of climate variability and length of rainy. Pdf climate variability in central equatorial africa. What controls equatorial atlantic winds in boreal spring. Remote influence of interdecadal pacific oscillation on. Contributions of atmospheric and oceanic feedbacks to.

This is characterized by strong seasurface temperature sst variability in the equatorial atlantic cold tongue act, where the amplitude of the sst seasonal cycle can reach 57 k. Less appreciated than this influence is how the tropical atlantic and indian oceans affect the pacific. Chiang,1,2 yochanan kushnir, and alessandra giannini3 lamontdoherty earth observatory of columbia university, palisades, new york, usa. Todd 1 and richard washington 2 1 department of geography, univers ity college london, 26 bedford. Published in 1990 by the american geophysical union.

Precipitation over northern south america and its seasonal. Regions of significant influence on unforced global mean. Northern south america is identified as one of the most vulnerable regions to be affected by climate change. Basin scale changes in the atmospheric forcing significantly affect the oceans properties and circulation. Moreover, regressions of observed atmospheric fields on equatorial atlantic sst anomalies indicate that cloud feedbacks over the namibian stratocumulus. Compared to enso, each of the three bjerknes feedback components, i. In particular, it makes naoatlantic ocean interactions not merely restricted to. In the ocean model micom the strength of the meridional overturning cell can be. Interactions among the pacific, atlantic and indian oceans through oceanatmosphere coupling can initiate andor modulate climate variability. Hence, the evaluation of rainfall simulations at seasonal and interannual time scales by the cmip5 models is urgently required. Equatorial atlantic variability and its relation to mean. Interdecadal gmt variability tends to be enhanced due to anomalous heat flux at the ocean surface over the western equatorial pacific, the southern ocean, and the subpolar north atlantic as well as at the top of the atmosphere over the equatorial and eastern pacific, over the weddell sea, and over baffin bay and the greenland sea. In terms of the mean state, the equatorial atlantic resembles the equatorial pacific in many aspects. Arctic amplification is a robust feature of climate response to global warming, with large impacts on ecosystems and societies.

Weakened sst variability in the tropical atlantic ocean since 2000. Enso and the north atlantic oscillation exert a strong influence on the northeast trades and sst over the northern tropical atlantic. Nevertheless, most of the cmip models show variability over the equatorial atlantic associated with a bjerknes feedback breugem et al. There has been considerable societal importance placed on the ability to distinguish and predict interannual anomalies of the tropical. Recent studies suggest that the interannual variability in the tropical pacific. On the relationship between atlantic nino variability and ocean. In this study, the influence of climate variability on crop yield is investigated by determining the degree of association between climatic indices and crop yields of maize and sorghum using spearmans rank correlation. Surface features such as the seasonal variations of the equatorial system of currents or of the. South of the equator, the upper layers are dominated by the westward drift of the south equatorial current, which, after reaching the coast of brazil near 8. A longstanding mystery is that a pronounced arctic warming occurred during the early 20th century when the rate of interdecadal change in radiative forcing was much weaker than at present. Weakened interannual variability of the contrast in. Tav exerts a strong influence on regional and global climate variability, altering the zonal and meridional atmospheric circulation cells and triggering global. Studying the influence of this variability on crop production is one measure of generating climate change resilience strategies. Growth and decay of the equatorial atlantic sst mode by.

The annual summer melts of arctic sea ice are up to twice as large in area as in the 20th century. This may change under greenhouse warming, but the mechanisms remain uncertain, thus limiting our ability to predict future changes in climate extremes. Download a pdf of all web pages for the instructors materials. Emergence of an equatorial mode of climate variability in. Go to previous content download this content share this content add this content to favorites go to next content. Frontiers growth and decay of the equatorial atlantic.

They also concluded that a mechanism similar to the windevaporationsst feedback 56 might play a role in the western equatorial atlantic. Hayes noaapacific marine environmental laboratory, seattle, washington journal of geophysical research, 95c8,195,208 1990 not subject to u. The focus is on the role that realistic diabatic heating and its vertical placement as well as surface temperature have in inducingreinforcing the local monthly wind circulation, the role that. Also, in the southeastern tropical atlantic seta, strong seasonal and. The influence of the different processes is compared by calculating the terms of the equation of heat conserva tion. While it is likely that feedbacks between marine biology and the reemergence and bridge processes influence climate variability, it is unlikely that the result would lead to oscillations with a preferred decadal period. The climate attributes that influence society, as noted earlier, are themselves influenced by a broad range of physical. Pdf equatorial atlantic variabilitymodes, mechanisms, and. Effect of ocean mesoscale variability on the mean state of. Characterizing the interannual variability of the equatorial paci. Deconstructing atlantic intertropical convergence zone variability. In the next section we study the evolution of the sst anomaly generated by the leading mode of winter atmospheric variability in the south atlantic. Using climate model simulations, we uncover the emergence of a mode of climate variability capable of generating unprecedented sea. The fact that the atlantic ocean is not just a heat reservoir providing sources and sinks of energy for nao variability, but also carries energy horizontally, introduces new features to atlantic airsea interactions.

Interannual variability on the influence of equatorial upwelling on biological productivity along 10ow in the eastern equatorial atlantic eea o. On the role of the south atlantic atmospheric circulation. To test the role of positive cloud feedbacks on atlantic climate variability, we perform model experiments using a stateoftheart agcm echam6, version 6. Another study disabled cloud feedbacks entirely to isolate the change in sst variability due to cloud feedback, but these authors were concerned with changes in the atlantic meridional overturning circulation and the atlantic multidecadal oscillation and did not consider the impact of ocean dynamics on cloud radiative feedback brown et al. The pacific ocean is home to enso which affects other oceans through atmospheric bridges and the oceanic indonesian throughflow itf. Variability in the eastern equatorial pacific ocean during 19861988 michael j. A stateoftheart climate model shows that radiative forcing due to anthropogenic and volcanic aerosols explains the variability in sea surface temperature of the north atlantic between 1950 and. Influence of the local crossequatorial sea surface temperature gradient and remote forcing from the eastern equatorial pacific. They find that the pattern of amo variability can be produced in a model that does not include ocean circulation changes, but only the effects of changes in air temperatures and winds.

The rainfall over the eastern equatorial pacific and equatorial atlantic is an. Impacts of the atlantic equatorial mode 2257 1 3 from the hadisst1 reconstruction rayner et al. Deconstructing atlantic intertropical convergence zone. Influence of arctic seaice variability on pacific trade.

In the closely coupled system of the equatorial oceans, wind variability in the western ocean basin for example can feed back directly to sst. The influence of the meridional overturning circulation on tropical atlantic climate and variability has been investigated using the atmosphereocean coupled model speedymicom miami isopycnic coordinate ocean model. Furthermore, recent extreme wet seasons over the region have induced socioeconomic impacts of wide proportions. Enhanced biennial variability in the pacific due to. The atlantic multidecadal oscillation without a role for. The ocean exerts a major influence on weather and climate by absorbing energy from the sun. Equatorial atlantic variabilitymodes, mechanisms, and. Phase locking of equatorial atlantic variability through. An objective tropical atlantic sea surface temperature. Starting from the hypothesis of two dominant influences on the itcz, namely, the cross. Both basins feature a warm pool in the west, a cold tongue in the. The influence of cloud feedbacks on equatorial atlantic.

The bjerknes positive feedback, involving equatorial zonal winds, sst, and. The flattened thermocline and reduced thermocline feedback weaken interannual variability of equatorial sea surface temperatures and guinea. The variability of equatorial thermocline spreading as an. Influence of the local crossequatorial sea surface temperature gradient and remote forcing from the eastern equatorial pacific john c. Oceanic ecosystems may profoundly influence previously hypothesized interdecadal climate mode loops in the pacific. As such, it is inherent to the atmosphere, but is affected by interactions between the atmosphere and the ocean, the biosphere, the land surface, and the cryosphere. Lmeteor in ihe equatorial atlantic along 220 w between 20 s and 30 n. Arctic sea ice, upper atmospheric circulation, surface wind, and seasurface temperature data provide evidence. Tropical atlantic variability is strongly biased in coupled general. Interannual variability on the influence of equatorial. A description of the seasonal cycle of the equatorial.

Presently, the indian ocean io resides in a climate state that prevents strong yeartoyear climate variations. In the present work we simulate the equatorial atlantic variability at annual and interannual timescales using a coupled mixed layer isopycnal ocean general circulation model ogcm forced with observations for the period 19801989. However, only a fraction of the observed atlantic nino events can be explained by the classical bjerknes feedback initiated by remote influence. Hounkonnou 4 1nigerian institute for oceanography and marine research, lagos, nigeria. The oceanic circulation in the tropicalequatorial atlantic is characterized by a complex array of currents and countercurrents that alternate in the horizontal and vertical planes fig. The variability of equatorial thermocline spreading. Rare ground data confirm significant warming and drying in. Sea surface temperature sst variability in the tropical atlantic ocean strongly impacts the.