{"627098":{"#nid":"627098","#data":{"type":"event","title":"PhD Defense by Anh Le-Duy Pham","body":[{"value":"\u003Cp\u003E\u003Cstrong\u003ECommittee members: \u003C\/strong\u003EDr. Taka Ito (advisor), Dr. Jennifer Glass, Dr.\u0026nbsp;Martial Taillefert, Dr. Joseph Montoya, and Dr. Thomas Weber\u003C\/p\u003E\r\n\r\n\u003Cp\u003ECOLLEGE OF SCIENCES\u003Cbr \/\u003E\r\nSCHOOL OF EARTH AND\u003Cbr \/\u003E\r\nATMOSPHERIC SCIENCES\u003Cbr \/\u003E\r\nEAS Ph.D. Defense\u003Cbr \/\u003E\r\nAnh Le-Duy Pham\u003Cbr \/\u003E\r\nOctober 18, 2019\u003Cbr \/\u003E\r\n12 PM\u003Cbr \/\u003E\r\nEarth and Atmospheric Sciences\u003Cbr \/\u003E\r\nFord Environmental Science \u0026amp;\u003Cbr \/\u003E\r\nTechnology (ES\u0026amp;T)\u003Cbr \/\u003E\r\n311 Ferst Drive, ES\u0026amp;T\u003Cbr \/\u003E\r\nAtlanta, GA 30332-0340\u003Cbr \/\u003E\r\nWeb: eas.gatech.edu\u003Cbr \/\u003E\r\nES\u0026amp;T\u003Cbr \/\u003E\r\n1387\u003Cbr \/\u003E\r\nTitle: Understanding ocean iron dynamics and impacts on marine\u003Cbr \/\u003E\r\necosystems\u003Cbr \/\u003E\r\nCommittee members: Dr. Taka Ito (advisor), Dr. Jennifer Glass, Dr. Martial\u003Cbr \/\u003E\r\nTaillefert, Dr. Joseph Montoya, and Dr. Thomas Weber\u003Cbr \/\u003E\r\nAbstract: Iron (Fe) is one of most the important nutrients for phytoplankton growth in the ocean,\u003Cbr \/\u003E\r\nmaking it a crucial element in the regulation of the ocean carbon balance and biogeochemical cycles.\u003Cbr \/\u003E\r\nAtmospheric deposition of Fe to the ocean has been increased due to human activities, which can\u003Cbr \/\u003E\r\nsignificantly alter the marine ecosystem. These necessitate a comprehensive understanding of how\u003Cbr \/\u003E\r\nthe ocean Fe cycling operates and how it will respond to human perturbations. In this work, we\u003Cbr \/\u003E\r\nidentify key mechanisms that control the ocean Fe cycle in various ocean basins and examine the\u003Cbr \/\u003E\r\nresponses of phytoplankton to an increasing Fe deposition using a global ocean biogeochemistry\u003Cbr \/\u003E\r\nmodel, constrained by a new high-quality dataset of the ocean Fe distribution.\u003Cbr \/\u003E\r\nIn the first two parts of the work, we refine the Fe parameterization in an ocean biogeochemistry\u003Cbr \/\u003E\r\nmodel and evaluate its ability in reproducing recent observations. We show that our new Fe scheme\u003Cbr \/\u003E\r\ndisplays a remarkable improvement over the old scheme. Through a suite of model simulations, we\u003Cbr \/\u003E\r\nreveal the crucial role of Fe release from particles and Fe retention by organic ligands in forming and\u003Cbr \/\u003E\r\nmaintaining the subsurface dissolved Fe (dFe) maxima observed in many ocean transects. The inclusion\u003Cbr \/\u003E\r\nof spatially varying ligand classes with different binding strengths in the model is important to explain\u003Cbr \/\u003E\r\nthe observed dFe pattern. We also identify the relative roles of different external dFe sources in\u003Cbr \/\u003E\r\ndifferent ocean basins. While the atmospheric deposition is an important source of dFe in the Atlantic\u003Cbr \/\u003E\r\nand Indian Oceans, sedimentary and hydrothermal dFe inputs are more important in the Pacific Ocean.\u003Cbr \/\u003E\r\nIn the third part of the work, we apply an unsupervised classification technique to analyze the dFe\u003Cbr \/\u003E\r\nbudget and the dFe distribution field simulated in different ocean Fe models. We suggest that the\u003Cbr \/\u003E\r\nupper ocean dFe patterns are modulated by interior ocean processes and that without an appropriate\u003Cbr \/\u003E\r\nrepresentation of these processes, Fe models cannot reproduce observations, even with a correct\u003Cbr \/\u003E\r\nmagnitude of the external fluxes. Our analysis also emphasizes a much more complex picture of the\u003Cbr \/\u003E\r\nocean Fe cycling than that of other nutrients such as phosphorus (P) and nitrogen (N).\u003Cbr \/\u003E\r\nIn the last part, we incorporate our improved Fe scheme into an ocean ecosystem model to investigate\u003Cbr \/\u003E\r\nthe response of the Indian Ocean ecosystem to an increasing atmospheric deposition of Fe. We found\u003Cbr \/\u003E\r\nthat while the diatom growth and export carbon flux are enhanced in the south of 40\u0366S, they decrease\u003Cbr \/\u003E\r\nin some regions in the northern Indian Ocean, compensated by increases in the coccolithophores\u003Cbr \/\u003E\r\ngrowth and carbonate carbon flux. These changes lead to a decrease in the carbon dioxide uptake\u003Cbr \/\u003E\r\nover the Indian Ocean.\u003C\/p\u003E\r\n","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":"","field_summary_sentence":[{"value":"Understanding ocean iron dynamics and impacts on marine ecosystems"}],"uid":"27707","created_gmt":"2019-10-03 15:25:24","changed_gmt":"2019-10-03 15:25:24","author":"Tatianna Richardson","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2019-10-18T13:00:00-04:00","event_time_end":"2019-10-18T15:00:00-04:00","event_time_end_last":"2019-10-18T15:00:00-04:00","gmt_time_start":"2019-10-18 17:00:00","gmt_time_end":"2019-10-18 19:00:00","gmt_time_end_last":"2019-10-18 19:00:00","rrule":null,"timezone":"America\/New_York"},"extras":[],"groups":[{"id":"221981","name":"Graduate Studies"}],"categories":[],"keywords":[{"id":"100811","name":"Phd Defense"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[{"id":"1788","name":"Other\/Miscellaneous"}],"invited_audience":[{"id":"78761","name":"Faculty\/Staff"},{"id":"78771","name":"Public"},{"id":"174045","name":"Graduate students"},{"id":"78751","name":"Undergraduate students"}],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}