Carbon Cycling Dynamics in the Seasonal Sea-Ice Zone of East Antarctica
Total Page:16
File Type:pdf, Size:1020Kb
Carbon cycling dynamics in the seasonal sea-ice zone of East Antarctica by Nicholas Patrick Roden BSc (Hons) Submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy at the Institute for Marine and Antarctic Studies (IMAS) November 2016 University of Tasmania i Declaration of originality This thesis contains no material which has been accepted for a degree or diploma by the University or any other institution, except by way of background information and duly acknowledged in the thesis, and to the best of my knowledge and belief no material previously published or written by another person except where due acknowledgement is made in the text of the thesis, nor does the thesis contain any material that infringes copyright. Nicholas Patrick Roden 17 November 2016 ii Authority of access This thesis may be available for loan and limited copying in accordance with the Copyright Act 1968. Nicholas Patrick Roden 17 November 2016 iii Statement regarding published work contained in this thesis The publishers of the papers compromising Chapter 2 and Chapter 3 hold the copyright for that content, and access to the material should be sought from the respective journals. The remaining non-published content of the thesis may be made available for loan and limited copying and communication in accordance with the Copyright Act 1968. Nicholas Patrick Roden 17 November 2016 iv For Mum and Dad v Table of contents List of tables ........................................................................................................................ ix List of figures ....................................................................................................................... x Statement of co-authorship .............................................................................................. xv Abstract ............................................................................................................................ xvii Acknowledgements ............................................................................................................ xx 1 Introduction ............................................................................................................ 1 1.1 The global carbon cycle ............................................................................................. 1 1.2 The Southern Ocean .................................................................................................. 2 1.3 Ocean acidification .................................................................................................... 4 1.4 Objectives of this study ............................................................................................. 5 2 Carbon cycling dynamics in the seasonal sea-ice zone of East Antarctica between 30°-80°E ......................................................................................................... 9 Abstract ................................................................................................................................ 9 2.1 Introduction.............................................................................................................. 10 2.2 Data and methods .................................................................................................... 12 2.2.1 Oceanographic setting of the Antarctic margin between 30°-80°E ................... 12 2.2.2 Biogeochemical measurements .......................................................................... 15 2.2.3 Net community production ................................................................................ 18 2.3 Results ....................................................................................................................... 19 2.3.1 Vertical sections of biogeochemical properties ................................................. 19 2.3.2 Distribution of sea-air CO2 flux and oxygen saturation ..................................... 23 2.3.3 Net community production ................................................................................ 27 2.4 Discussion ................................................................................................................. 29 2.4.1 CO2 uptake and storage ...................................................................................... 29 2.4.2 Surface water biogeochemical cycling ............................................................... 33 2.5 Conclusion ................................................................................................................ 36 Acknowledgments ............................................................................................................. 37 Appendix A: Underway measurements .......................................................................... 39 Appendix B: Dissociation constants ................................................................................ 41 Appendix C: Salinity normalization ................................................................................ 42 Appendix D: Net community production ........................................................................ 43 Appendix E: Partitioning of oxygen saturation .............................................................. 45 Appendix F: Additional sections ...................................................................................... 46 vi 3 Annual cycle of carbonate chemistry and decadal change in coastal Prydz Bay, East Antarctica .................................................................................................. 51 Abstract .............................................................................................................................. 51 3.1 Introduction.............................................................................................................. 52 3.2 Data and methods .................................................................................................... 54 3.2.1 Oceanographic setting ........................................................................................ 54 3.2.2 Sampling and analytical procedure .................................................................... 54 3.2.3 Sea-ice thickness measurements ........................................................................ 59 3.2.4 Air-sea CO2 flux calculations ............................................................................. 60 3.2.5 Controls on total dissolved inorganic carbon ..................................................... 62 3.2.6 Error analysis ..................................................................................................... 63 3.3 Results ....................................................................................................................... 64 3.3.1 Physical parameters ............................................................................................ 64 3.3.2 Total alkalinity ................................................................................................... 65 3.3.3 Total dissolved inorganic carbon ....................................................................... 65 3.3.4 Nutrients ............................................................................................................. 68 3.3.5 Calculated carbonate parameters ........................................................................ 71 3.4 Discussion ................................................................................................................. 73 3.4.1 Net community production ................................................................................ 73 3.4.2 Decadal change in carbonate chemistry ............................................................. 74 3.5 Conclusion ................................................................................................................ 76 Acknowledgments ............................................................................................................. 77 4 Manipulating seawater pH under sea-ice: carbonate chemistry of an in-situ Antarctic free ocean CO2 enrichment experiment .................................................. 79 Abstract .............................................................................................................................. 79 4.1 Introduction.............................................................................................................. 80 4.2 Data and methods .................................................................................................... 81 4.2.1 Experimental setting........................................................................................... 82 4.2.2 CO2 enriched seawater ....................................................................................... 83 4.2.3 Seabed experimental setup ................................................................................. 83 4.2.4 Pump system and hoses ...................................................................................... 84 4.2.5 Sensor array ........................................................................................................ 85 4.2.6 Control of pH ..................................................................................................... 85 4.2.7 Biogeochemical measurements .......................................................................... 85 4.3 Results ......................................................................................................................