Aitor Aldama Campino Atmospheric and oceanic circulation play an important role on Earth's climate system. In this thesis the interaction between these components Atmospheric and oceanic is analysed using thermodynamical and biogeochemical coordinates. Stream functions implemented in general coordinates have been used to circulation from a simplify the complexity of the system and facilitate the understanding of the different processes. thermodynamic perspective Atmospheric and oceanic circulation from a thermodynamic perspective thermodynamic a from Atmospheric and oceanic circulation Aitor Aldama Campino Aitor Aldama Campino holds a BSc in Physics from the University of the Basque Country and a MSc in Atmospheric science, Oceanography and Climate from Stockholm University. He started his PhD in 2014. ISBN 978-91-7797-827-5 Department of Meteorology Doctoral Thesis in Atmospheric Sciences and Oceanography at Stockholm University, Sweden 2019 Atmospheric and oceanic circulation from a thermodynamic perspective Aitor Aldama Campino Academic dissertation for the Degree of Doctor of Philosophy in Atmospheric Sciences and Oceanography at Stockholm University to be publicly defended on Thursday 24 October 2019 at 10.00 in De Geersalen, Svante Arrhenius väg 14. Abstract The climate system is continuously transporting and exchanging heat, freshwater, carbon and other tracers in different spatio-temporal scales. Therefore, analysing the system from a thermodynamic or biogeochemical framework is highly convenient. In this thesis the interaction between the ocean and the atmospheric circulation is analysed using thermodynamical and biogeochemical coordinates. Due to the dimensionality of the climate system stream functions are used to reduce this complexity and facilitate the understanding of the different processes that take place. The first half of this thesis, focuses on the interaction between the atmospheric and the ocean circulation from a thermodynamic perspective. We introduce the hydrothermohaline stream function which combines the atmospheric circulation in humidity-potential temperature (hydrothermal) space and the ocean circulation in salinity-temperature coordinates (thermohaline). A scale factor of 7.1 is proposed to link humidity and salinity coordinates. Future scenarios are showing an increase of humidity in the atmosphere due to the increase of temperatures which results in a widening of the hydrothermal stream function along the humidity coordinate. In a similar way, the ocean circulation in the thermohaline space expands along the salinity coordinate. The link between salinity and humidity changes is strongest at net evaporation regions where the gain of water vapour in the atmosphere results in a salinification in the ocean. In addition, the ocean circulation in latitude-carbon space is investigated. By doing so, we are able to distinguish the roles of different water masses and circulation pathways for ocean carbon. We find that the surface waters in the subtropical gyres are the main drivers of the meridional carbon transport in the ocean. By separating the carbon in its different constituents we show that the carbon transported by the majority of the water masses is a result of the solubility pump. The contribution of the biological pump is predominant in the deep Pacific Ocean. The effects of the Mediterranean Overflow Waters on the North Atlantic are discussed in the final part of the thesis. Keywords: Atmospheric circulation, Ocean circulation, Stream functions. Stockholm 2019 http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-172842 ISBN 978-91-7797-827-5 ISBN 978-91-7797-828-2 Department of Meteorology Stockholm University, 106 91 Stockholm ATMOSPHERIC AND OCEANIC CIRCULATION FROM A THERMODYNAMIC PERSPECTIVE Aitor Aldama Campino Atmospheric and oceanic circulation from a thermodynamic perspective Aitor Aldama Campino ©Aitor Aldama Campino, Stockholm University 2019 ISBN print 978-91-7797-827-5 ISBN PDF 978-91-7797-828-2 Cover image: wave breaking in Meñakoz Cove, Basque Country. Photo by Jon del Rivero. Printed in Sweden by Universitetsservice US-AB, Stockholm 2019 To my parents Bego and Josu Abstract The climate system is continuously transporting and exchanging heat, fresh- water, carbon and other tracers in different spatio-temporal scales. Therefore, analysing the system from a thermodynamic or biogeochemical framework is highly convenient. In this thesis the interaction between the ocean and the at- mospheric circulation is analysed using thermodynamical and biogeochemical coordinates. Due to the dimensionality of the climate system, stream functions are used to reduce this complexity and facilitate the understanding of the dif- ferent processes that take place. The first half of this thesis, focuses on the interaction between the atmo- spheric and the ocean circulation from a thermodynamic perspective. We intro- duce the hydrothermohaline stream function which combines the atmospheric circulation in humidity-potential temperature (hydrothermal) space and the ocean circulation in salinity-temperature coordinates (thermohaline). A scale factor of 7.1 is proposed to link humidity and salinity coordinates. Future scenarios are showing an increase of humidity in the atmosphere due to the in- crease of temperatures which results in a widening of the hydrothermal stream function along the humidity coordinate. In a similar way, the ocean circula- tion in the thermohaline space expands along the salinity coordinate. The link between salinity and humidity changes is strongest at net evaporation regions where the gain of water vapour in the atmosphere results in a salinification in the ocean. In addition, the ocean circulation in latitude-carbon space is investigated. By doing so, we are able to distinguish the roles of different water masses and circulation pathways for ocean carbon. We find that the surface waters in the subtropical gyres are the main drivers of the meridional carbon transport in the ocean. By separating the carbon in its different constituents we show that the carbon transported by the majority of the water masses is a result of the solubility pump. The contribution of the biological pump is predominant in the deep Pacific Ocean. The effects of the Mediterranean Overflow Waters on the North Atlantic are discussed in the final part of the thesis. Sammanfattning Klimatsystemet transporterar och utbyter kontinuerligt värme, sötvatten, kol och andra markörer i olika skalor för tid och rum. Därför är det mycket prak- tiskt att analysera systemet med ett termodynamiskt eller biogeokemiskt syn- sätt. I denna avhandling analyseras interaktionen mellan havets och atmos- färens cirkulation genom nyttjandet av termodynamiska och biogeokemiska koordinater. På grund av klimatsystemets dimensionalitet användes ström- funktioner för att minska komplexiteten och underlätta förståelsen för de olika processerna. Den första halvan av denna avhandling fokuserar på interaktionen mellan atmosfärens och havets cirkulation ur ett termodynamiskt perspektiv. Vi in- troducerar den hydrotermohalina strömfunktionen som kombinerar den atmos- färiska cirkulationen i koordinater av luftfuktighet och potentiell temperatur (hydrotermisk) med havets cirkulation i koordinater av salinitet och temperatur (termohalin). En skalfaktor på 7,1 föreslås för att sammankoppla luftfuktighet och salinitetskoordinater. Framtida scenarier visar en ökning av luftfuktigheten i atmosfären på grund av temperaturökningar som resulterar i en utvidgning av den hydrotermiska strömfunktionen längs fuktkoordinaten. På liknande sätt expanderar havets cirkulation i det termohalina rummet längs salinitetskoordi- naten. Kopplingen mellan förändringar i salinitet och luftfuktighet är starkast vid regioner med nettoavdunstning, där avdunstningen av vattenånga i atmos- fären resulterar i en försaltning av havet. Dessutom undersöks havets cirkulation i latitud-kolrummet. Därmed kunde vi skilja på olika vattenmassor och cirkulationsvägar för kolet i havet. Vi finner att ytvattnet i de subtropiska virvlarna är den viktigaste drivkraften för den meridionala koltransporten i havet. Genom att dela upp kolet i dess olika beståndsdelar visar vi att kolet som transporteras av majoriteten av vatten- massorna är ett resultat av löslighetspumpen. Den biologiska pumpens bidrag är dominerande i det djupa Stilla havet. Effekterna av Medelhavets överflödes- vatten på Nordatlanten diskuteras i den sista delen av avhandlingen. Laburpena / Resumen Lurreko klima sistemak etengabe El sistema climático está con- garraiatzen eta trukatzen ditu beroa, tinuamente transportando e inter- ura, karbonoa eta bestelako adier- cambiando calor, agua dulce, car- azleak espazio-denbora eskala des- bono y otros trazadores en difer- berdinetan. Hortaz, sistema ikus- entes escalas espacio-temporales. Por puntu termodinamiko edo biokimiko lo tanto, analizar el sistema desde batetik aztertzea oso egokia da. Tesi un marco termodinámico o biogeo- honetan ozeanoen eta atmosferaren químico es muy conveniente. En esta zirkulazioen arteko elkarrekintzak ko- tesis, la interacción entre las circula- ordenatu termodinamikoak eta bio- ciones oceánica y atmosférica es anal- geokimikoak erabiliz aztertu egin izada utilizando coordenadas termod- dira. Klima-sistemaren dimentsion- inámicas y biogeoquímicas. Debido a altasuna dela eta, korronte funtzioak la gran dimensionalidad del sistema erabili dira konplexutasun hori mur- climático, las funciones de corriente rizteko eta bertan jazotzen diren son utilizadas para reducir