Title Page
Contents
LIST OF ACRONYMS 11
ABSTRACT 17
CHAPTER 1. INTRODUCTION 20
1.1. Background 21
1.1.1. Importance of Arctic sea ice 21
1.1.2. Radiative Forcing 27
1.2. Motivation 37
1.3. Objective of this research 40
1.4. Structure of the thesis 41
CHAPTER 2. STUDY AREA AND DATA 43
2.1. Study Area 44
2.1.1. Geographic features of the Arctic 44
2.1.2. Spatial definition of the Arctic 47
2.2. Data 52
2.2.1. Surface Albedo 52
2.2.2. Skin temperature 55
2.2.3. Sea ice concentration 57
2.2.4. Sea Surface Temperature 60
2.2.5. Radiative Kernels 61
CHAPTER 3. Methodology 72
3.1. Sea Ice Radiative Forcing 73
3.2. Evaluation of radiative forcing 77
CHAPTER 4. Results 82
4.1. Spatiotemporal characteristics of radiative kernels 83
4.2. Annual characteristic of SIRFs in the Arctic 91
4.3. Seasonal characteristic of SIRFs in the Arctic 100
4.4. Monthly Characteristic of SIRFs in the Arctic 111
CHAPTER 5. Discussion and Limitation 118
5.1. Evaluation of radiative kernels 119
5.1.1. Comparison with TOA radiation 119
5.1.2. Difference according to GCMs 126
5.2. Radiative forcing in areas of sea ice loss 130
5.3. Evaluation of sea ice surface temperature products in the Arctic 137
5.4. Sea ice Feedback from radiative forcing 146
CHAPTER 6. CONCLUSION 155
6.1. Conclusion 156
6.2. Application 164
6.3. Recommendations for the further research 167
REFERENCES 170
Table 2.1. Summary of datasets used in the study. 71
Table 2.2. SIRF input variables 76
Table 4.1. SIRFs annual change according to region. 99
Table 4.2. SIRFs seasonal change according to region. 110
Table 5.1. Monthly net-SIRF change according to GCM 129
Table 5.2. Monthly radiative forcing due to sea ice loss. 136
Table 5.3. Summary of previous research on kernel-based feedback 149
Table 5.4. Sea ice feedback according to research area and factors. 151
Figure 2.1. Arctic Definitions 49
Figure 2.2. Location map in the Arctic regions. 50
Figure 4.1. Temporal distribution of surface albedo radiative kernel (all-sky) monthly means according to GCM. 84
Figure 4.2. Spatial distribution of surface albedo radiative kernels for the month of June 86
Figure 4.3. the spatial distribution of the difference between CAM5 and GFDL surface albedo radiative kernel. 87
Figure 4.4. Temporal distribution of surface temperature radiative kernel (all-sky) monthly means according to GCM. 88
Figure 4.5. Spatial distribution of surface temperature radiative kernels for the month of July. 89
Figure 4.6. the spatial distribution of the difference between HadGEM3 and CAM5 surface albedo radiative kernel. 90
Figure 4.7. Time series distribution of annual average SIRF according to the GCMs from 1982 to 2015 in the Arctic (a) net-SIRF, (b) albedo-SIRF, (c) Temperature-SIRF. 92
Figure 4.8. Spatial distribution of the annual change in SIRFs for each factor based on mean of five radiative kernels. (a) Net-SIRF, (b) Albedo-SIRF, (c) Temperature-SIRF. 94
Figure 4.9. The seasonal average SIRFs according to GCMs. (a) December-January–February period, (b) March–April–May period, (c) June-July-... 101
Figure 4.10. Seasonal SIRFs using the average the kernels of GCMs for each factor. The horizontal line represents the period, and the vertical line represents the radiative forcing for each factor (Net-SIRF, Albedo-SIRF, Temperature-SIRF). 106
Figure 4.11. Temporal distribution of the monthly Net-SIRF using the average of five radiative kernels. 113
Figure 4.12. Temporal distribution of the monthly Net-SIRF according to GCMs. The thick line represents the net-SIRF with the applied mean value of 5 GCMs kernel, while the shading indicates the range of SIRF according to the GCMs. 114
Figure 4.13. The SIRFs monthly changes for each factor from 1982 to 2015. 115
Figure 4.14. Spatial distribution of the Net-SIRF monthly change. 117
Figure 5.1. Annual change in TOA shortwave radiation and kernel-based radiation according to surface albedo change. 122
Figure 5.2. Annual change in TOA longwave radiation and kernel-based radiation according to skin temperature change. 125
Figure 5.3. Spatial distribution of sea ice concentration. (a) 1983, (b) 2005, (c) 1983 versus 2005 sea ice loss areas (yellow) 131
Figure 5.4. Average surface temperatures from 2000 to 2015 for June. (a) ERA5 (b) MODIS (c) Average MODIS valid pixels (%) (d) Histogram of... 139
Figure 5.5. average surface temperature of ERA5 and MODIS over sea ice during the summer season 141
Figure 5.6. Average surface temperatures from 2000 to 2015 for December. (a) ERA5 (b) MODIS (c) Average MODIS valid pixels (%) (d) Histogram of... 142
Figure 5.7. average surface temperature of ERA5 and MODIS over sea ice during the summer season 143