Yuanyang Xie, Tingting Liu, Na Li, Ruibo Lei. Changes in area fraction of sediment-laden sea ice in the Arctic Ocean during 2000 to 2021[J]. Acta Oceanologica Sinica.
Citation:
Yuanyang Xie, Tingting Liu, Na Li, Ruibo Lei. Changes in area fraction of sediment-laden sea ice in the Arctic Ocean during 2000 to 2021[J]. Acta Oceanologica Sinica.
Yuanyang Xie, Tingting Liu, Na Li, Ruibo Lei. Changes in area fraction of sediment-laden sea ice in the Arctic Ocean during 2000 to 2021[J]. Acta Oceanologica Sinica.
Citation:
Yuanyang Xie, Tingting Liu, Na Li, Ruibo Lei. Changes in area fraction of sediment-laden sea ice in the Arctic Ocean during 2000 to 2021[J]. Acta Oceanologica Sinica.
Chinese Antarctic Center of Surveying and Mapping, Wuhan University, Wuhan 430079, China
2.
Key Laboratory of Polar Environment Monitoring and Public Governance, Wuhan University, Wuhan 430079, China
3.
MNR Key Laboratory for Polar Science, Polar Research Institute of China, Shanghai 200136, China
Funds:
The National Key Research and Development Program of China under contract No. 2021YFC2803304; the National Natural Science Foundation of China under contract No. 42325604; the Program of Shanghai Academic/Technology Research Leader under contract No. 22XD1403600; the Fundamental Research Funds for the Central Universities under contract No. 2042024kf0037; the Key Laboratory for Polar Science, Ministry of Natural Resources, Polar Research Institute of China, under contract No. KP202004.
Sediment-laden sea ice plays an important role in Arctic sediment transport and biogeochemical cycles, as well as the shortwave radiation budget and melt onset of ice surface. However, at present, there is a lack of efficient observation approach from both space and in situ for the coverage of Arctic sediment-laden sea ice. Thus, both spatial distribution and long-term changes in area fraction of such ice floes are still unclear. This study proposes a new classification method to extract Arctic sediment-laden sea ice on the basic of the difference in spectral characteristics between sediment-laden sea ice and clean sea ice in the visible band using the MOD09A1 data with the resolution of 500 m, and obtains its area fraction over the pan Arctic Ocean during 2000−2021. Compared with Landsat-8 true color verification images with a resolution of 30 m, the overall accuracy of our classification method is 92.3%, and the Kappa coefficient is 0.84. The impact of clouds on the results of recognition and spatiotemporal changes of sediment-laden sea ice is relatively small from June to July, compared to that in May or August. Spatially, sediment-laden sea ice mostly appears over the marginal seas of the Arctic Ocean, especially the continental shelf of Chukchi Sea and the Siberian Seas. Associated with the retreat of Arctic sea ice extent, the total area of sediment-laden sea ice in June–July also shows a significant decreasing trend of 8.99 × 104 km2 per year. The occurrence of sediment-laden sea ice over the Arctic Ocean in June–July leads to the reduce of surface albedo over the ice-covered ocean by 14.1%. This study will help thoroughly understanding of the role of sediment-laden sea ice in the evolution of Arctic climate system and marine ecological environment, as well as the heat budget and mass balance of sea ice itself.
Figure 1. A resized true color MOD09A1 image over the Arctic on June 18, 2018.
Figure 2. Coverage of Landsat-8 images used as ground truth data in 2018 and the trajectory of the 9th Chinese National Arctic Research Expedition (CHINARE) during July–September 2018.
Figure 3. Reflectance of various surface features (left) and corresponding MODIS true color sub-scenes (right).
Figure 4. Histograms of frequency distributions of reflectance of MODIS Band 1, 3, and 4 and three defined classification indices for three mixed pixel cases.
Figure 5. MOD09A1 and Landsat-8 true color images on 18 June 2018. a and b. Original scenes of MOD09A1 and Landsat-8; c and d. cropped sub-scenes from Landsat-8 and MOD09A1, respectively.
Figure 6. Sediment-laden sea ice photograph (a) and clean sea ice photograph (b) taken on board R/V Xuelong on August 3, 2018 and the corresponding classified result of MODIS obtained on August 5, 2018 (c).
Figure 7. Classification results of the Arctic Ocean during May to September in 2018.
Figure 8. Seasonal variation of the averages and standard deviations for area fraction (a) and actual area (b) of sediment-laden sea ice, clean sea ice, open water, and cloud, and total sea ice in the study area during 2000–2021.
Figure 9. Probability of occurrence of sediment-laden sea ice and clouds at each grid in June and July during 2000–2021. The orange and red dashed lines in (a) are the 25% and 50% contour lines, respectively.
Figure 10. Interannual variations for area fractions of sea ice, sediment-laden sea, clean sea ice, open water and cloud averaged in June and July during 2000–2021.
Figure 11. Interannual variations for average sediment-laden sea ice area in June and July, average sea ice extent in June and July, annual minimum sea ice extent and average sea ice extent from June to the time with annual minimum ice extent during 2000–2021.
Figure 12. Seasonal variation of $ {\alpha }_{\mathrm{v}\mathrm{i}\mathrm{s}} $, $ {\alpha }_{\mathrm{r}\mathrm{e}\mathrm{g}1} $, and $ {\alpha }_{\mathrm{r}\mathrm{e}\mathrm{g}2} $ within the study region averaged in June and July during 2000–2021.
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