climate(change(&(coastal( upwellingdrivers · ebuss. filled circles represent trends that are...

Climate Change & Coastal Upwelling Drivers

Marisol García-‐Reyes, William J. Sydeman, David S. Schoeman, Ryan R. Rykaczewski, Bryan A. Black, Sarah Ann Thompson, Arthur Miller,

Andrew Bakun & Steven J. Bograd

Third InternaFonal Symposium \ Santos City, Brazil Effects of Climate change on the World’s Ocean \ March, 2015

!

bakun hypothesis !

!

poleward migration of pressure systems

climate change impact on upwelling drivers

Bakun et al. 2015

bakun hypothesis


Bakun, 1990

image by Bakun et al. 2015

Trends consistent with Bakun hypothesis of increasing upwelling favorable winds !18 studies 187 records (non-‐ind) !+ others that support it

+ Barton et al. 2014 + Cropper et al. 2014 + Alves et al. 2013 + Bylhouwer et al. 2013 + de Castro et al. 2014 + Jacox et al. 2014 + Stocker et al. 2013

Sydeman et al., 2014

Meta-analysis of upwelling wind trends


20th century reanalysis SLP climatologies

1940-2010may-july dec-feb

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poleward migration of pressure systems

Bakun et al., 2015

Rykaczweski et al., submi\ed

meridional gradient of wind trends in climate models

and robust in the CalCS and HCS. Nevertheless, the trend is statisticallysignificant for half of the models and the multimodel mean (ExtendedData Fig. 5).

The intensification of upwelling in both hemispheres over the courseof the twenty-first century suggests that the underlying mechanism isrelated to global climate change. Bakun proposed that greenhouse warm-ing would strengthen upwelling across the globe through differentialland–sea surface heating because excessive summertime warming overland relative to the ocean intensifies the continental thermal lows adja-cent to upwelling regions, thus increasing atmospheric pressure gradientsand alongshore upwelling-favourable winds6. To test this hypothesis,we regressed the summertime upwelling intensity against the land–seasurface temperature difference at the high latitudes of the EBUSs between1950 and 2099. Figure 4 shows that the increase in upwelling intensityis highly correlated with the increase in land–sea temperature differ-ence in the CanCS, the HCS, the BCS and, to a lesser degree, the CalCS.This robust relationship between the land–sea temperature differenceand upwelling intensity supports Bakun’s hypothesis, and suggests alink between greenhouse warming and the intensification of upwelling.The increase in coastal upwelling under climate change is also linked tochanges in upwelling phenology because the onset and termination ofthe upwelling season correspond to the times of the year when the wind-driven coastal current changes from downwelling to upwelling, and viceversa. Hence, the projected year-round increase in upwelling-favourablewinds causes the upwelling season to start earlier, end later and last longer(Extended Data Fig. 7).

Although the latitudinal trends in upwelling intensification are gen-erally consistent across regions, certain patterns are region-specific and

probably influenced by localized climate phenomena. For instance, theCalCS does not show intensification and the CanCS shows a robust weak-ening trend at the two lowest latitudes. Such differences among theEBUSs are probably the result of regional factors. Upwelling in the CalCSis strongly influenced by natural climate variability such as the El Nino/Southern Oscillation, Pacific Decadal Oscillation and North Pacific GyreOscillation23–26, whose effects on upwelling may override those predictedby Bakun’s hypothesis. In the CanCS, an increase in the land–sea thermaldifference is expected to strengthen the southwesterly monsoon circu-lation that drives downwelling-favourable winds in the subtropics, amechanism that may explain the reduction in upwelling intensity at lowlatitudes27. Additionally, the poleward shift of subtropical anticyclonesalso tends to weaken upwelling-favourable winds at low latitudes28.Describing how such regional processes interact with global greenhouseforcing will be critical to further resolve the dynamics of upwelling in awarming climate.

The lengthening and strengthening of upwelling at high latitudes andthe resulting reduction in its latitudinal heterogeneity may have pro-found ecological impacts. On local scales, the climate-mediated inten-sification of upwelling could promote the productivity of fisheries andmarine ecosystems by bringing more nutrient-rich waters to the surface,where they can subsidize the base of the food web4. Alternatively, theincreased supply of such nutrient-rich and oxygen-poor waters fromdepth could have adverse effects on marine life by allowing hypoxic con-ditions to develop over large swaths of the coastal ocean and causing massdie-offs29. These contrasting effects of upwelling intensification bothdepend on the continued delivery of nutrient-rich waters to the surfacevia upwelling. However, increased solar heating due to greenhouse warm-ing could enhance stratification, deepen the thermocline and thus preventcool and nutrient-rich waters from being upwelled4,30. Such a decouplingof upwelling from the supply of nutrient-rich waters would jeopardizethe persistence of fisheries and the functioning of marine ecosystems.

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Figure 2 | Linear trends in upwelling duration and intensity. Multimodelmeans (solid lines) and 95% bootstrap confidence intervals (shading) of lineartrends in upwelling duration (a, b) and intensity (c, d) for 1950–2099 for all fourEBUSs. Filled circles represent trends that are robust across climate models(that is, at least 50% of the models show a statistically significant trend and atleast 80% of those agree on the sign of the trend). The bootstrap confidenceintervals are computed from 999 samples.

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Figure 3 | Spatial standard deviations of upwelling duration and intensity.Multimodel means (thick lines) and 95% bootstrap confidence intervals(shading) of spatial standard deviation of upwelling duration (a) and intensity(b) for 1950–2099 for all four EBUSs. The thin straight lines indicate lineartrends in the multimodel mean time series. The bootstrap confidence intervalsare computed from 999 samples.

RESEARCH LETTER

3 9 2 | N A T U R E | V O L 5 1 8 | 1 9 F E B R U A R Y 2 0 1 5

Macmillan Publishers Limited. All rights reserved©2015

Wang et al., 2015






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Sydeman, fig2, x43p3wind trends by latitude in meta-analysis

Expansion of the Hadley cell under global warming

Jian Lu,1,2 Gabriel A. Vecchi,3 and Thomas Reichler4

Received 11 October 2006; revised 9 February 2007; accepted 21 February 2007; published 24 March 2007.

[1] A consistent weakening and poleward expansion of theHadley circulation is diagnosed in the climate changesimulations of the IPCC AR4 project. Associated with thiswidening is a poleward expansion of the subtropical dryzone. Simple scaling analysis supports the notion that thepoleward extent of the Hadley cell is set by the locationwhere the thermally driven jet first becomes baroclinicallyunstable. The expansion of the Hadley cell is caused by anincrease in the subtropical static stability, which pushespoleward the baroclinic instability zone and hence the outerboundary of the Hadley cell. Citation: Lu, J., G. A. Vecchi,and T. Reichler (2007), Expansion of the Hadley cell under globalwarming, Geophys. Res. Lett., 34, L06805, doi:10.1029/2006GL028443.

1. Introduction

[2] The Hadley cell (HC) plays a pivotal role in theearth’s climate by transporting energy and angular momen-tum poleward and by organizing the three dimensionaltropical atmospheric circulation. The locations of thelarge-scale subtropical dry zones and the major tropical/subtropical deserts of the globe are largely determined bythe subsiding branches of the HC. Thus, understanding howthe structure and intensity of the HC and the associatedsubtropical dry zones may change under the greenhouse gas(GHG)-induced global warming is a topic of substantialinterest.[3] The detailed response of the HC to increasing GHG is

complex, as the HC is influenced by many factors, involv-ing tropical heating processes [e.g., Mitas and Clement,2006], the atmospheric stability [e.g., Schneider, 1977],extra-tropical eddy dynamics [e.g., Walker and Schneider,2006], and total atmospheric moisture [Frierson et al.,2006]. To date, studies of the long term behavior of theHC, and the extent to which GHG forcing is relevant remaininconclusive. Atmospheric reanalyses show a statisticallysignificant intensification of their Hadley circulationthroughout the second part of the 20th century [Mitas andClement, 2005]. However, this intensification is not foundin the rawinsonde data, nor in most 20th century simulations

using both coupled or atmosphere-only general circulationmodels (GCMs) [Mitas and Clement, 2005, 2006]. Mean-while, simple physical arguments [e.g., Betts, 1998;Knutson and Manabe, 1995; Held and Soden, 2006] predicta slowdown of the overall tropical overturning circulationunder global warming. Such a slowdown seems to be arobust feature in GCMs [Vecchi and Soden, 2007], and hasbeen identified in observational analyses of the Walkercirculation [Vecchi et al., 2005; Zhang and Song, 2006].[4] However, it remains to be seen whether it also

projects onto the zonally averaged part of the circulation.Analysis of the satellite observations indicates a polewardexpansion of the HC over the past 27 years [Fu et al., 2006].The extent to which this observed widening of the HC isprimarily a response to GHG warming is not clear andwarrants further investigation.[5] Here, we investigate the response of the HC to global

warming using 21st century increasing GHG scenarios fromthe Fourth Assessment Report (AR4) of the Intergovern-mental Panel on Climate Change (IPCC). The diversity ofthe numerical schemes and parameterizations of the AR4models provides a unique framework for understanding theresponse of the HC to GHG increases. In this study weshow that there is a robust poleward expansion and weak-ening of the Hadley circulation across all models, and weidentify a possible mechanism for this behavior.

2. Data and Methods

[6] Gridded global monthly precipitation, evaporation,surface air temperature, surface wind, temperature, meridi-onal wind, and 500hPa pressure velocity (w500) wereretrieved from the AR4 archive website (available athttp://www-pcmdi.llnl.gov), and annual means were formedfor the analysis. Most of our analysis was based on outputfrom the A2 scenario which is at the upper end of GHGemission (the CO2 concentration reaches 800 ppm at the endof the 21st century), two less aggressive scenarios were alsoexplored (A1B with CO2 stabilization at 720ppm and B1with CO2 stabilization at 550pm). Only the first ensemblemember of each of the 14–15 models (depending on theavailability of the variables) was used. To identify theclimate change response, we compared the first and lasttwenty years of the 21st century, i.e., (2081–2100) minus(2001–2020).[7] To determine the poleward edges of the HC, we

computed the zonal-mean mass flux stream function (y)by vertically integrating the zonal-mean density-weightedmeridional wind component from the top model leveldownward. We first determined the maximum of the abso-lute value of this stream function at 500 hPa (y500), andthen identified the edges of the HC as the first latitudepoleward of the maximum at which y500 became zero. Analternative definition of the HC edge as the transition

GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L06805, doi:10.1029/2006GL028443, 2007

1Climate and Global Dynamics Division, National Center forAtmospheric Research, University Corporation for Atmospheric Research,Boulder, Colorado, USA.

2University Corporation for Atmospheric Research Visiting ScientistProgram, Geophysical Fluid Dynamics Laboratory, NOAA, PrincetonUniversity, Princeton, New Jersey, USA.

3Geophysical Fluid Dynamics Laboratory, National Oceanic andAtmospheric Administration, Princeton University, Princeton, New Jersey,USA.

4Department of Meteorology, University of Utah, Salt Lake City, Utah,USA.

Copyright 2007 by the American Geophysical Union.0094-8276/07/2006GL028443$05.00

L06805 1 of 5

Expansion of the Hadley cell under global warming

Jian Lu,1,2 Gabriel A. Vecchi,3 and Thomas Reichler4

Received 11 October 2006; revised 9 February 2007; accepted 21 February 2007; published 24 March 2007.

[1] A consistent weakening and poleward expansion of theHadley circulation is diagnosed in the climate changesimulations of the IPCC AR4 project. Associated with thiswidening is a poleward expansion of the subtropical dryzone. Simple scaling analysis supports the notion that thepoleward extent of the Hadley cell is set by the locationwhere the thermally driven jet first becomes baroclinicallyunstable. The expansion of the Hadley cell is caused by anincrease in the subtropical static stability, which pushespoleward the baroclinic instability zone and hence the outerboundary of the Hadley cell. Citation: Lu, J., G. A. Vecchi,and T. Reichler (2007), Expansion of the Hadley cell under globalwarming, Geophys. Res. Lett., 34, L06805, doi:10.1029/2006GL028443.

1. Introduction

[2] The Hadley cell (HC) plays a pivotal role in theearth’s climate by transporting energy and angular momen-tum poleward and by organizing the three dimensionaltropical atmospheric circulation. The locations of thelarge-scale subtropical dry zones and the major tropical/subtropical deserts of the globe are largely determined bythe subsiding branches of the HC. Thus, understanding howthe structure and intensity of the HC and the associatedsubtropical dry zones may change under the greenhouse gas(GHG)-induced global warming is a topic of substantialinterest.[3] The detailed response of the HC to increasing GHG is

complex, as the HC is influenced by many factors, involv-ing tropical heating processes [e.g., Mitas and Clement,2006], the atmospheric stability [e.g., Schneider, 1977],extra-tropical eddy dynamics [e.g., Walker and Schneider,2006], and total atmospheric moisture [Frierson et al.,2006]. To date, studies of the long term behavior of theHC, and the extent to which GHG forcing is relevant remaininconclusive. Atmospheric reanalyses show a statisticallysignificant intensification of their Hadley circulationthroughout the second part of the 20th century [Mitas andClement, 2005]. However, this intensification is not foundin the rawinsonde data, nor in most 20th century simulations

using both coupled or atmosphere-only general circulationmodels (GCMs) [Mitas and Clement, 2005, 2006]. Mean-while, simple physical arguments [e.g., Betts, 1998;Knutson and Manabe, 1995; Held and Soden, 2006] predicta slowdown of the overall tropical overturning circulationunder global warming. Such a slowdown seems to be arobust feature in GCMs [Vecchi and Soden, 2007], and hasbeen identified in observational analyses of the Walkercirculation [Vecchi et al., 2005; Zhang and Song, 2006].[4] However, it remains to be seen whether it also

projects onto the zonally averaged part of the circulation.Analysis of the satellite observations indicates a polewardexpansion of the HC over the past 27 years [Fu et al., 2006].The extent to which this observed widening of the HC isprimarily a response to GHG warming is not clear andwarrants further investigation.[5] Here, we investigate the response of the HC to global

warming using 21st century increasing GHG scenarios fromthe Fourth Assessment Report (AR4) of the Intergovern-mental Panel on Climate Change (IPCC). The diversity ofthe numerical schemes and parameterizations of the AR4models provides a unique framework for understanding theresponse of the HC to GHG increases. In this study weshow that there is a robust poleward expansion and weak-ening of the Hadley circulation across all models, and weidentify a possible mechanism for this behavior.

2. Data and Methods

[6] Gridded global monthly precipitation, evaporation,surface air temperature, surface wind, temperature, meridi-onal wind, and 500hPa pressure velocity (w500) wereretrieved from the AR4 archive website (available athttp://www-pcmdi.llnl.gov), and annual means were formedfor the analysis. Most of our analysis was based on outputfrom the A2 scenario which is at the upper end of GHGemission (the CO2 concentration reaches 800 ppm at the endof the 21st century), two less aggressive scenarios were alsoexplored (A1B with CO2 stabilization at 720ppm and B1with CO2 stabilization at 550pm). Only the first ensemblemember of each of the 14–15 models (depending on theavailability of the variables) was used. To identify theclimate change response, we compared the first and lasttwenty years of the 21st century, i.e., (2081–2100) minus(2001–2020).[7] To determine the poleward edges of the HC, we

computed the zonal-mean mass flux stream function (y)by vertically integrating the zonal-mean density-weightedmeridional wind component from the top model leveldownward. We first determined the maximum of the abso-lute value of this stream function at 500 hPa (y500), andthen identified the edges of the HC as the first latitudepoleward of the maximum at which y500 became zero. Analternative definition of the HC edge as the transition

GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L06805, doi:10.1029/2006GL028443, 2007

1Climate and Global Dynamics Division, National Center forAtmospheric Research, University Corporation for Atmospheric Research,Boulder, Colorado, USA.

2University Corporation for Atmospheric Research Visiting ScientistProgram, Geophysical Fluid Dynamics Laboratory, NOAA, PrincetonUniversity, Princeton, New Jersey, USA.

3Geophysical Fluid Dynamics Laboratory, National Oceanic andAtmospheric Administration, Princeton University, Princeton, New Jersey,USA.

4Department of Meteorology, University of Utah, Salt Lake City, Utah,USA.

Copyright 2007 by the American Geophysical Union.0094-8276/07/2006GL028443$05.00

L06805 1 of 5

- IPCC AR4 models (3rd generation) - poleward expansion of hadley cells: - poleward displacement of subduction cells (ocean high pressure systems) - poleward expansion of mid-latitude dry zones (thermal low pressure systems)

Thermodynamic and Dynamic Mechanisms for Large-Scale Changes in theHydrological Cycle in Response to Global Warming*

RICHARD SEAGER AND NAOMI NAIK

Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York

GABRIEL A. VECCHI

Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey

(Manuscript received 3 February 2010, in final form 29 April 2010)

ABSTRACT

Themechanisms of changes in the large-scale hydrological cycle projected by 15models participating in theCoupled Model Intercomparison Project phase 3 and used for the Intergovernmental Panel on ClimateChange’s Fourth Assessment Report are analyzed by computing differences between 2046 and 2065 and 1961and 2000. The contributions to changes in precipitationminus evaporation,P2E, caused thermodynamicallyby changes in specific humidity, dynamically by changes in circulation, and by changes in moisture transportsby transient eddies are evaluated. The thermodynamic and dynamic contributions are further separated intoadvective and divergent components. The nonthermodynamic contributions are then related to changes in themean and transient circulation. The projected change in P 2 E involves an intensification of the existingpattern ofP2Ewithwet areas [the intertropical convergence zone (ITCZ) andmid- to high latitudes] gettingwetter and arid and semiarid regions of the subtropics getting drier. In addition, the subtropical dry zonesexpand poleward. The accentuation of the twentieth-century pattern ofP2E is in part explained by increasesin specific humidity via both advection and divergence terms. Weakening of the tropical divergent circulationpartially opposes the thermodynamic contribution by creating a tendency to decreasedP2E in the ITCZ andto increasedP2E in the descending branches of theWalker andHadley cells. The changingmean circulationalso causes decreased P 2 E on the poleward flanks of the subtropics because the descending branch of theHadley Cell expands and the midlatitude meridional circulation cell shifts poleward. Subtropical drying andpoleward moistening are also contributed to by an increase in poleward moisture transport by transienteddies. The thermodynamic contribution to changing P 2 E, arising from increased specific humidity, isalmost entirely accounted for by atmospheric warming under fixed relative humidity.

1. Introduction

The models that were run as part of the CoupledModel Intercomparison Project phase 3 (CMIP3; Meehlet al. 2007a), and used for the Intergovernmental Panelon Climate Change’s FourthAssessmentReport (IPCCAR4), robustly predict large-scale changes in the hy-drological cycle as a consequence of rising greenhousegases and resulting global warming. To zeroth orderthese can be described as ‘‘wet getting wetter and dry

getting drier’’ or ‘‘rich-get-richer.’’ That is, already wetareas of the deep tropics and midlatitudes will getwetter and arid and semiarid regions in the subtropicswill get drier (Held and Soden 2006;Meehl et al. 2007b;Chou et al. 2009). Such large-scale changes to the hy-drological cycle, if they occur, will have importantconsequences for human societies and ecosystems. Forexample, already wet areas could be subject to increasedflooding, while already dry areas could see further re-ductions of available water and water quality as theytransition to a drier climate. Even though all of the24 models that were used within IPCC AR4 exhibitthis change in the hydrological cycle, albeit with dif-ferences, it is important to know exactly how it occursand why. Such knowledge will enable a better assess-ment of the reliability of the climate model pro-jections.

* Lamont-DohertyEarthObservatoryContributionNumber 7374.

Corresponding author address:Richard Seager, Lamont-DohertyEarth Observatory, Columbia University, 61 Rt. 9W, Palisades, NY10964.E-mail: [email protected]

1 SEPTEMBER 2010 S EAGER ET AL . 4651

DOI: 10.1175/2010JCLI3655.1

! 2010 American Meteorological Society

The main argument to date for why wet regions willget wetter and dry regions get drier is that of Held andSoden (2006).1 First of all, the reason that precipitationPminus evaporationE, the net flux of water substance atthe earth’s surface, varies so much spatially is because ofthe transport of water vapor (and, to a much lesser ex-tent, condensate) in the atmosphere by the mean andtime-varying flow. The wettest regions on the planet arein the deep tropics, where the trade winds converge withmoisture and P exceeds E. Monsoonal regions are otherplaces where P 2 E is strongly positive. In some mid-and high-latitude regions, there are also regions ofstrong P 2 E, with the atmospheric moisture conver-gence being supplied by a mix of transient eddies (stormsystems) and the mean flow in planetary stationarywaves. The coasts of northwestern North America andnorthwestern Europe are examples. In the subtropicalregions, a combination of moisture divergence by thetrade winds, stationary waves, and transient eddies causestrongly negative P 2 E over the oceans. As Held andSoden (2006) point out, a warming atmosphere will causean increase in atmospheric water vapor. Hence, even ifthe circulation were to remain fixed, it would be expectedthat the transports of water vapor would intensify.Consequently, under these assumptions, the pattern ofP 2 E will remain the same but the values will becomemore extreme, making wet regions wetter and dry re-gions drier.As Held and Soden (2006) show (their Fig. 7), simply

assuming that specific humidity will rise according to theClausius–Clapeyron relation with fixed relative humid-ity leads to a prediction of the change in P 2 E whichmatches very well with that actually projected by theCMIP3/IPCC AR4 models. This agreement argues forthe importance of thermodynamic controls on changingP 2 E. However, as also seen in their Fig. 7, this simpleargument predicts increasing P 2 E over all land areas.This is because, in the absence of unquenchable surfacewater supply (like the ocean), the climatological meanP 2 E has to be zero or positive averaged over a catch-ment basin and balanced by surface and subsurface flowback to the ocean. However, there are many regionswhere, in contrast to the simple argument, P 2 E be-comes less positive over land (e.g., southwestern NorthAmerica; Seager et al. 2007). Further, Held and Soden(2006) also show that the simple thermodynamic pre-diction of changingP2E cannot account for a polewardexpansion of the latitude that, in the zonal mean,

separates the region of negative P2 E in the subtropicsand positive P 2 E in midlatitudes. Further, Chou et al.(2009) have shown that within the tropics, dynamicalchanges (e.g., changes in vertical motion and conver-gence zone shifts) are required, along with changes inhumidity, to entirely explain changes in precipitation.Consequently, a full accounting of projected changes in

P2E requires an extension of theHeld and Soden (2006)argument. In particular, the extent to which changes inatmospheric circulation affect P 2 E as well as themechanisms for changes in P 2 E over land and howchanges in transient eddy moisture fluxes, either due tochanges in eddy intensity or location, affect P 2 E allneed to be evaluated. In this paper we will

1) Conduct a detailed analysis of the changes in themoisture budget in the twenty-first century for the 15CMIP3/IPCC AR4 models for which all the neededdata were archived and made available.

2) Break down the changes in moisture budget intothose due to changes in specific humidity (the ther-modynamic component), mean circulation (the dy-namic component), and transient eddy moisture fluxconvergence.

3) Relate the dynamic components of the moisture bud-get change to changes in the circulation.

This extends work already done by Seager and Vecchi(2010) by completing the moisture budget breakdownand taking a global perspective compared to their NorthAmerican focus. The work provides the most thoroughaccount to date of projected changes in the atmospherichydrological cycle that are anticipated as a consequenceof rising greenhouse gases.

2. Models and methods

We examined all 24 models that comprise the CMIP3database (Meehl et al. 2007a) and that were used as partof the IPCC AR4 to check that all the data required tocalculate a moisture budget were available. This re-quires daily data for specific humidity and winds onstandard pressure levels.Only 15models, listed inTable 1,had all of the needed data (some models had all thedata but contained a lot of bad humidity data that couldnot be reasonably fixed, so these models were dis-carded). With these 15 models, we performed moisturebudget calculations for two periods for which daily datawere saved: 1961–2000 and 2046–65. The 1961–2000simulations were forced with historical trace gas, aero-sol, solar and volcanic forcings, and, in some cases,changes in land use, albeit with differences betweenmodels in how these forcings were treated; the 2046–65simulations used the ‘‘middle of the road’’ emissions

1 Emori and Brown (2005) performed a very different means ofbreaking down precipitation changes into ‘‘dynamic’’ and ‘‘ther-modynamic’’ components based on the probability density func-tion of the vertical velocity field.

4652 JOURNAL OF CL IMATE VOLUME 23

blame the hadley cells …

SLP climatologies for peak upwelling season

20th century reanalysis

SLP linear trends: 1940-2013

hPa/decade

may may

decemberdecember

decadal variability in pressure systems

correlation between wind and pressure systems

García-‐Reyes et al., 2014

OH: ocean high pressure system !CTL: thermal low pressure system

correlation between wind and pressure systems


summary

bakun hypothesis: consistent with data in last decades, but mechanism not supported

poleward migration of pressure systems: not observed in past data large multi-decadal variability

higher impact of eastern side of ocean highs


conclusions

bakun hypothesis: consistent with data in last decades, but mechanism not supported

poleward migration of pressure systems: not observed in past data large multi-decadal variability

higher impact of eastern side of ocean highs next step: change on coastal pressure gradients in relation to both pressure systems

climate(change(&(coastal( upwellingdrivers · ebuss. filled circles represent trends that are...

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