Figure captions
Figure 1. (a) The study area and (b–f) sampling locations in Lützow-Holm Bay, Eastern Antarctica. MODIS-Terra satellite images were obtained on (b) 19 January 2019, (d) 24 April 2015 at site JARE57_EM, (e) 25 April 2017 at site JARE59_POPs, and (f) 18 March 2018 at sites JARE60_KU1 and JARE60_KU2. The images in (d−f) show the sea-ice condition before winter at each coring site; dark areas indicate where the sea ice was broken, and the cores obtained from these sites were first-year ice. The background image in (c) is an Advanced Land Observing Satellite (ALOS)/Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) image obtained on 26 January 2010 by the Japan Aerospace Exploration Agency (JAXA).
Figure 2. Vertical profiles of (a, c) salinity and (b, d) δ18O values in snow, first-year ice cores (left), and multi-year ice cores (right). Horizontal solid lines at 0 cm depth indicate the snow–ice interface. Dashed lines in (b, d) show the δ18O value of under-ice water (−0.7‰) sampled during JARE60. The photo in (a) is a vertical thin section of the top 5 cm of core JARE60_KU2.
Figure 3. (a) Vertical profiles of salinity and δ18O values in core JARE57_P31.5 compared to (b) its ice structure. (c–f) Representative vertical thin section photographs are provided for each ice structure.
Figure 4. Vertical profiles of (a, e) NO3, (b, f) PO43−, (c, g) Si(OH)4, and (d, h) chl.a concentrations in first-year ice (top) and multi-year ice cores (bottom). Horizontal solid lines at a depth of 0 cm indicate the snow–ice interface. The photo in (c) and (d) is the ice algae community assemblage for the bottom of core JARE60_KU1.
Figure 5. Plots of (a) PO43−, (b) Si(OH)4, (c) NO3, and (d) NO2 concentrations versus snow fraction in multi-year ice cores.
Figure 6. Time series of the mean snow fraction in the top 200 cm of each multi-year ice core from 2015 (core JARE56_NMS) to 2018 (core JARE59_2).
Figure 7. Plots of (a, b) Si(OH)4, (c, d) PO43−, (e, f) NO3, and (g, h) NO2 concentrations versus salinity in first-year (left) and multi-year ice cores (right). Dilution lines are based on the nutrient concentrations and salinity of under-ice water.
Figure 8. Dissolved inorganic nitrogen (DIN = NO3 + NO2) versus PO43− concentrations in multi-year ice cores. The red solid line indicates the Redfield ratio (DIN:P = 16:1) and the black dashed line indicates the ratio for uptake by diatoms (DIN:P = 12:1) (Takeda, 1998).
Figure 9. Vertical profiles of N* (Equation 3) and chl.a concentrations in multi-year ice cores (a) JARE56_NMS and (b) JARE57_P31.5.
Figure 10. Conceptual illustration of the evolution of nutrient concentrations produced by photosynthesis and remineralization during the desalination process from new ice to first-year ice to multi-year ice.