ANALYSIS of WATER MASSES DISTRIBUTION and CIRCULATION in the WHITE SEA, RUSSIA. by LAURENT LATCHE a Thesis Submitted to the Univ

University of Plymouth PEARL https://pearl.plymouth.ac.uk 04 University of Plymouth Research Theses 01 Research Theses Main Collection 2004 Analysis of water masses distribution and circulation in the White Sea, Russia Latche, Laurent http://hdl.handle.net/10026.1/635 University of Plymouth All content in PEARL is protected by copyright law. Author manuscripts are made available in accordance with publisher policies. Please cite only the published version using the details provided on the item record or document. In the absence of an open licence (e.g. Creative Commons), permissions for further reuse of content should be sought from the publisher or author. ANALYSIS OF WATER MASSES DISTRIBUTION AND CIRCULATION IN THE WHITE SEA, RUSSIA. by LAURENT LATCHE A thesis submitted to the University of Plymouth In partial fulfilment for the degree of DOCTOR OF PHILOSOPHY School of Earth, Ocean and Environmental Sciences Faculty of Science March 2004 ANALYSIS OF WATER MASSES DISTRIBUTION AND CIRCULATION IN THE WHITE SEA, RUSSIA. by Laurent Latche ABSTRACT The White Sea is a semi-enclosed sea, which consists of several bays and estuaries connected to the open ocean through the narrow and shallow Gorlo Strait. Several studies have been carried out in the region during the last decade in order to investigate the potential threat of anthropogenic pollutants. However, the temporal and spatial resolution of such experiments has been inadequate to resolve issues such as the dispersion and propagation of environmentally hazardous substances. The present investigation uses in-situ measurements of temperature and salinity gathered at high spatio-temporal resolution for the first time, as part of the FNTAS project "Mesoscale physical and biogeochemical processes in coastal waters of the Russian Arctic" and of a number of Russian national and EU research projects. The study focuses on the formation, evolution and spatial distribution of fine-scale thermohaline structures. The mixing processes were thoroughly studied in the southwest area of the Gorlo Strait, where present water masses have an important contribution in the dynamics of the White Sea including water-exchange and deep-water renewal. Satellite images were used to estimate the mesoscale circulation and the contribution of freshwater inputs to the formation and distribution of the water mass structure. Smaller scale mixing processes were also investigated using a statistical method of fine structure-inhomogeneity analysis in order to assess the intensities of the diapycnal and isopycnal modes of small-scale mixing. The results showed i) the intrusion of mixed layers into the White Sea initially formed in the Gorlo area due to tidal mixing of the saline Barents Sea waters and the While Sea waters. The mixed layers were traced across the whole section, in the vicinity of an active boundary layer in a form of a domed structure, which separates from stagnant deep-water masses of the White Sea. ii) The formation of shelf-edge dense water was revealed in Kandalaksha Bay suggesting cascading phenomena, iii) A detailed study of the mixing processes in Gorlo revealed four interacting water masses: the Gorlo Strait Water (GSW), the White Sea Surface Water (WSSW), the Dvina Bay Water, and the White Sea Intermediate Water. Mesoscale "lens" of WSSW was observed in the near- surface layer associated with a thermal front, which resulted in the formation of an intrusion of the GSW into the White Sea Basin, facilitated by the Terskii Coastal Current and the cyclonic Dvina Bay gyre, iv) The spatial distribution of temperature and salinity fluctuations within the water masses revealed the intensity of mixing and demonstrated the thermohaline transformation of the Gorlo Strait Waters during its mesoscale displacement at the intermediate depths across the northern part of the White Sea. The findings of this study therefore provide a better understanding of the deep water renewal mechanisms in the White Sea. The classical concepts suggest that the saline waters of the Barents Sea enter the White Sea and sink at the entrance carrying with them all potential pollutants. The present study supports the hypothesis that the Barents Sea water is transformed at the Gorlo Strait and subsequently is propagated in the form of mixed layers across the White Sea until they reach the shelf of Kandalaksha Bay, where they finally sink. CONTENTS ABSTRACT 3 CONTENTS 4 LIST OF FIGURES 7 LIST OF TABLES 12 ACKNOWLEDGMENTS H AUTHOR'S DECLARATION 15 CHAPTER 1: INTRODUCTION 16 1.1. BACKGROUND 16 1.2. MOTIVATION 16 1.3. OBJECTIVES n 1.4. APPROACH 17 1.5. WIDER DISSEMINATION 18 1.6. OUTLINE OF THESIS 1 8 CHAPTER 2: LITERATURE REVIEW 19 2.1. INTRODUCTION 19 2.2. OVERVIEW OF PROCESSES IN SEMI-ENCLOSED SEAS 19 2.3. CASCADING PHENOMENA 23 2.4. FINE THERMOHALINE STRUCTURE 26 2.5. DESCRIPTIVE OCEANOGRAPHY OF THE WHITE SEA 32 2.5.1. Introduction 32 2.5.2. Topographic features and volume of waters 34 2.5J. Water Masses 35 2.5.4. Atmospheric conditions 38 2.5.5. Tidal conditions 40 2.5.6. Fresh water inflow 4! 2.5.7. Interactions and hy drological signatures 43 2.5.8. Mixing processes 45 2.5.9. Large-scale circulation and characteristics 47 CHAPTER 3: OBSERVATIONAL PROGRAMME AND METHODOLOGY 50 3.1. INTRODUCTION 50 3.2. FIELD SITES AND CTD MEASUREMENTS 52 3.2.1. Survey 2000 52 3.2.2. Survey 2001 56 3.3. CTD DATA PROCESSING 56 3.3.1. Sea-Bird Electronic module software 58 3.4. CALCULATION OF THE HORIZONTAL DISTRIBUTION OF PARAMETERS 61 3.5. DYNAMIC HEIGHT 62 3.6. COLLECTION AND PROCESSING OF REMOTE SENSED DATA 62 3.6.1. Sea Surface Temperature images 62 3.6.2. SLA products. 63 3.6.3. Processing SLA data and calculating geostrophic surface velocity 65 3.7. DISCUSSION 65 CHAPTER 4: FINE THERMOHALINE STRUCTURES IN THE WHITE SEA 67 4.1. INTRODUCTION 67 4.2. STRUCTURES OF WATER MASSES 68 4.3. DISTRIBUTION OF SURFACE WATERS 71 4.4. DISTRIBUTION OF INTERMEDIATE WATERS 74 4.5. IDENTIFICATION OF MIXED LAYERS: STEPS 78 4.5.1. Distribution of step A 78 4.5.2. Distribution of step B 80 4.5.3. Distribution of step C S! 4.5.4. Distribution of step D 82 4.5.5. Distribution of step E 82 4.5.6. Vertical structure of the steps 84 4.6. A SUMMER THERMOHALINE TNTRUSLON 86 4.7. A EXJME-SHAPE STRUCTURE 88 4.8. CONCLUSION 90 CHAPTER 5: INTERANNUAL VARIABILITY OF THE WATER MASS STRUCTURE 93 5.1. INTRODUCTION 93 5.2. HYDROGRAPHICAL RESULT2001 94 5.2.1. CTDprofiles 94 5.2.2. Identification of mixed layers: Steps 96 5.2.3. Distribution of water masses 99 5.2.4. The shape of the mixed layers 104 5.3. INTER-SEASONAL COMPARISON OF WATER STRUCTURE 106 5.3.1. A persistent thermohaline intrusion 106 5.3.2. Dense water formed on the coastal slopes of Kandalaksha Bay. 113 5.3.3. Dome-shape structure and internal oscillation in deep layers 122 5.4. DISCUSSION 123 5.5. CONCLUSION 126 CHAPTER 6: MIXING PROCESSES WEST OF THE GORLO STRAIT 128 6.1. INTRODUCTION 128 6.2. MATERIALS AND OBSERVATIONS 129 6.3. WATER MASSES IN CONTACT 131 6.4. MESOSCALE EDDY FORMATION 134 6.5. INTRUSION OF TME GSW 137 6.6. FRONTAL ZONES AND MIXING AREAS 140 6.7. INTENSITY OF MIXING PROCESSES 149 6.8. CONCLUSION 155 CHAPTER 7: ESTIMATES OF MESOSCALE CIRCULATION 157 7.1. INTRODUCTION 157 7.2. THE USE OF SATELLITE IMAGES 158 7.2. /. SSTandin-situ temperature distribution 161 7.2.2. SLA and dynamic height 163 7.2.3. Mesoscale eddy act ivit ies from SLA and SST 165 7.2.4. Summary of validating satellite images 166 7.3. THE WHITE SEA CIRCULATION IN JUNE-JULY 2000 166 7.3.1. Entrance of the White Sea: the Gorlo Strait 167 7.3.2. White Sea Bays and the Basin 167 7.4. DISCUSSION 168 7.5. CONCLUSION 170 CHAPTER 8: ISOPYCNAL AiND DIAPYCNAL ANALYSIS ON THE CORLO STRAIT WATER DISPLACEMENT 172 8.1. INTRODUCTION 172 8.2. MATERIAL AND METHODS 173 8.2.1. The GSW displacement 173 8.2.2. Statistical method of fine structure inhomogeneity analysis 175 8.3. ANALYSIS OF SMALL SCALE STRUCTURES 177 83.1. The(pS\ aT') plane 177 8.3.2. Isopycnal and Diapycnal mode of mixing 177 8.3.3. The mode of small-scale mixing west of Gorlo Strait 180 8.3.4. Spatial distribution of the transformed GSW: intensities of diapycnal and isopycnal mode 182 8.3.5. Modes of mixing of the GSW in Kandalaksha Bay 185 8.4. CONCLUSION 19I CHAPTER 9: CONCLUSION 192 9.1. SUMMARY OF THE RESULTS 192 9.2. RECOMMENDATIONS FOR FUTURE WORK 195 APPENDIX A: LOG BOOK STATION AND COMPUTING PROGRAMS 196 A. 1. TABLE INFO CRUISE 2000 196 A.2. TABLE INFO CRUISE 2001 199 A.3. MATLAB PROGRAMS: DEPTHSECTION.M 200 A.4. N4ATLAB PROGRAMS: INTERPOL.M 201 A.5. MATLAB PROGRAMS: DYNTOPO.M 202 A. 6. FORTRAN PROGRAM: READSLA.FOR 203 APPENDIX B: MIXED LAYER IDENTIFICATION 205 B. 1 SALINITY AND DENSITY DISTRIBUTION AT THE EAST-WEST TRANSECT 205 B. 2 TABLES OF THE THERMOHALINE INDEX OF THE MIXED LAYERS A, B, C, D, E - SURVEY 2000 207 APPENDIX C: MIXED LAYER IDENTIFICATION 215 C. I TABLES OF THERMOHALINE INDEX OF THE MIXED LAYERS F, C, D, E - SURVEY 2001 215 APPENDIX D: PROFILES OF TEMPERATURE AND SALINITY FLUCTUATIONS WEST OF THE GORLO STRAIT - SURVEY 2000 219 APPENDIX E: PANEL OF SST AND SLA MAPS 222 APPENDIX F: FINE STRUCTURE INHOMOGENEITIES ANALYSIS 243 A.7. F.l PLATES ((iS\ aT') AT STATIONS DURJNG SURVEY 2000 243 F.2 PLATES (pS', aT') AT STATIONS DURJNG SURVEY 2001 247 REFERENCES 251 RELEVANT PUBLICATIONS 262 LIST OF FIGURES Chapter 2 Figure 2.1: Schematic representation ofcascading (Cooper and Vaux, 1949) during winter at stations A, B, C of same water properties.

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