The Tides in a General Circulation Model in the Indonesian Sras Dwiyoga Nugroho
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The tides in a general circulation model in the indonesian sras Dwiyoga Nugroho To cite this version: Dwiyoga Nugroho. The tides in a general circulation model in the indonesian sras. Ocean, Atmosphere. Université Paul Sabatier - Toulouse III, 2017. English. NNT : 2017TOU30089. tel-01897523 HAL Id: tel-01897523 https://tel.archives-ouvertes.fr/tel-01897523 Submitted on 17 Oct 2018 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. THTHESEESE`` En vue de l’obtention du DOCTORAT DE L’UNIVERSITE´ DE TOULOUSE D´elivr´epar : l’Universit´eToulouse 3 Paul Sabatier (UT3 Paul Sabatier) Pr´esent´eeet soutenue le 30/06/2017 par : Dwiyoga NUGROHO La mar´ee dans un mod`elede circulation g´en´erale dans les mers Indon´esiennes JURY Isabelle Dadou Pr´esidente Professeur-Universit´ePaul Sabatier,FRANCE Eric Chassignet Rapporteur Professeur-Florida State University,USA Janet Sprintall Rapporteur Senior scientist-Scripps-UC San Diego,USA Brian Arbic Examinateur Professeur associ´e-Michigan State University,USA Agus Atmadipoera Examinateur Maˆıtrede conf´erence-Bogor Agricultural University,INDONESIA Ariane Koch-larrouy Directrice de Th´ese LEGOS-IRD,FRANCE Florent Lyard Co-Directeur de Th´ese LEGOS-IRD,FRANCE Philippe Gaspar Co-Directeur de Th´ese CLS,FRANCE Ecole´ doctorale et sp´ecialit´e: SDU2E : Oc´ean,Atmosph`ere, Climat Unit´ede Recherche : Laboratoire d’Etudes en G´eophysiqueet Oc´eanographie Spatiales (UMR5566) 2 Acknowledgments Alhamdulillahirabbil alamiin..... The work presented in this thesis was a huge collaborative effort from Ministry of Marine Affairs and Fisheries-Indonesia (MMAF), Institut Fran¸caisIn- donesia, Collecte Localisation Satellites(CLS)-France, Laboratoire d’Etudes en G´eophysique et Oc´eanographieSpatiales(LEGOS)-France, MERCATOR Ocean-France and University of Paul Sabatier-France. As a result of the large number of contributing parties, I apologize for to those whose names may be unintentionally omitted. My sincerest gratitude goes to my advisors, first to my major advisor Dr.Ariane Koch-Larrouy for her patience and encouragement to achieve my best and for guiding me through the research presented in this thesis. Secondly, thanks to Dr.Florent Lyard as my second advisor, his insight, his beyond text book numerical skills have continuously inspired me. Thirdly thanks to Dr.Philippe Gaspar for his encouragement and support throughout my PhD study. I would like to express the deepest appreciation to Mr. Berny Achmad Subki, Dr.Aryo Hang- gono, Dr.Aulia Riza, Mrs.Yenung Secasari, Prof Dietrich Bengen(IPB), Prof Ita Widowati(UNDIP), Dr.Vincent Siregar(IPB) for all their support during the INDESO scholarship program. Ap- preciation is further extended to my colleagues at Agency for Marine Research and Fisheries (BALITBANG-KP) specially to Teja Arief, Elvan Ampou, Marza Ihsan, Nurazmi Ratna, Rinny Rahmania, Niken Gusmawati, Budi Gunadharma, Romy Adrianto, Indra Hermawan, Iis Triyu- lianti, Dendy Mahabror, Falia Maunantia, Bambang Adithya, Nurman Mbay, Pak Usep Nas- rudin, Pak Imam, Pak Dono, Mba Titi Lestari and Mas Hilman Ramadhan. I am especially grateful to my jury and reviewer members, Thanks to Prof. Eric Chassignet, Dr.Janet Sprintall as my thesis reviewer for their careful review of my manuscript, and for the comments, corrections and suggestions that ensued. Thanks to Prof Isabelle Dadou, Prof Brian Arbic and Dr.Agus Sholeh Atmadipoera for assisting me during my thesis defense. 3 The most important part of my time at LEGOS,CLS and MERCATOR has been knowing such an incredible group of scientist and administrative team. I feel very fortunate to have been part of them and would like to thank to Sara Fleury(LEGOS), Florence Bouille(CLS), BenoˆıtTran- chant(CLS), Jerome Chanut(Mercator),Guillaume Reffray(Mercator), Rachid Benshila (LE- GOS), Damien Allain(LEGOS), Julien Jouanno (LEGOS), the ECOLA research team (LE- GOS), GESSEC LEGOS(Martine Mena, Nadine Lacroux, Brigite Cournou Agathe Barithaud) and the head of LEGOS Dr.Alexandre Ganachaud. And thanks to my friends in LEGOS: Ma- rine Bretagnon, Cory Pegliasco, Kevin Gueriero, Marine Rog´e,Michel Tchilibou, Dac Nguyen, for your friendship and surprise gift after my defense. I would like also to thank each of those who touched my life, making Toulouse as a such a wonderful home for me. ”Terima kasih” to PPI Toulouse (Indonesian Student Association in Toulouse) and Ibu Ninik, Ibu Yunah, Ibu Bintang from AAI(Franco-Indonesian Association). A special thanks to my lovely pretty wife, Munky Andi Kasim, my adorable daughters Azkanayra Zaida Nugroho and Azraina Zahira Nugroho for your warm hugs and kiss everyday and also my brother,my brother in-law, my sister and my sister in-law. Finally, I dedicate this thesis to my parents Rachmat Musa and Titiek Lasmiyati and my parents in-law Nash Andi Kasim and Jenny Loenggana. I can never thank them enough for all that they have given me .....Thank you. 4 Abstract In the Indonesian seas, large tidal currents interact with the rough topography and create strong internal waves at the tidal frequency, called internal tides. Part of them will eventually propagate and dissipate far away from generation sites. Their associated mixing upwells cold and nutrient-rich water that prove to be critical for climate system and for marine resources. This thesis uses the physical ocean general circulation model, NEMO, as part of the INDESO project that aims at monitoring the Indonesian marine living resources. Models not taking into account tidal missing are unable to correctly reproduce the vertical structure of watermasses in Indonesian seas. However, taking into account this mixing is no simple task as the phenomena involved in tidal mixing cover a wide spectrum of spatial scales. Internal tides indeed propagate over thousands of kilometres while dissipation and mixing occurs at centimetric to millimetric scales. A model capable of resolving all these processes at the same time does not exist. Until now scientists either parameterised the tidal mixing or used models which only partly resolve internal tides. More and more scientists introduce explicit tidal forcing in their models but without knowing where the energy is going and how the internal tides are dissipated. This thesis intends to quantify energy dissipation in NEMO forced with explicit tidal forcing and compares it to the dissipation induced by the currently used parameterization. This thesis also provides new results about the quantification of the tidal energy budget in NEMO. I first contributed to an INDESO study that aimed at validating the model against several observation data sets. In a second and third study, I investigated the mixing produced in the model by explicit tidal forcing and its impact on water mass. Explicit tides forcing proves to produce a mixing comparable to the one produced by the parameterization. It also produces a significant cooling of 0.3 °C with maxima reaching 0.8°C in the areas of internal tide generation. The cooling is stronger on austral winter. The spring tides and neap tides modulate this impact by 0.1°C to 0.3°C. The model generates 75% of the expected internal tides energy, in good agreement with other previous studies. In the ocean interior, most of it is dissipated by horizontal momentum dissipation (19 GW), while in reality one would expect dissipation through vertical possesses. This value is close to the dissipation induced by the parameterization (16 GW). The mixing is strong over generation sites, and only 20% remains for far field dissipation mainly in the 5 Banda and Sulawesi Seas. The model and the recent INDOMIX cruise [Koch-Larrouy et al. (2015)], which provided direct estimates of the mixing, are surprisingly in good agreement mainly above straits. However, in regions far away from the energy generation sites where INDOMIX found NO evidence of intensified mixing, the model produces too strong mixing. The bias comes from the lack of specific set up of internal tides in the model. More work is thus needed to improve the modeled dissipation, which is a theme of active research for the scientific community. I dedicated the last part of my thesis to the quantification of tidal energy sinks in NEMO. I first worked on a simple academic case: the COMODO internal tides test case, which analyses the behaviour of a vertically stratified fluid forced by a barotropic flow interacting over an idealized abyssal plain/slope/shelf topography without bottom friction. The results of the finite element T-UGOm hydrodynamic model are compared with those of NEMO. The central issue in calculating tidal energy budget is the separation of barotropic and baroclinic precesses. To this aim we developed an original method based on the projection on vertical modes. At first glance, this method compares well with the classical method of separation using the vertically averaged current. However, when looking into more details at energy budgets, vertical modes allow a cleaner and more realistic separation between barotropic and baroclinic tides. This precision will be very useful for the future SWOT mission. Also this method of separation allows quantification of the energy associated with each mode. This allowed us to identify an important bias in NEMO: The higher the mode is the shorter the NEMO wavelengths become compared to the T-UGOm wavelengths. NEMO also produces a strong numerical mixing that erodes the barotropic tides on the abyssal plain, where there is no bottom friction. The best suspect might be the 2D/3D coupling scheme implied by the NEMO’s time splitting.