Introduction
The supporting information file describes biogeochemical data obtained from the offshore slope to the ice front of the Totten Ice Shelf (TIS) during the spring/summer of 2018, 2019, and 2020.
Oceanographic observations were conducted on the continental shelf slope near the TIS in mid–February 2019 during the 10th Antarctic survey by R/V Kaiyo Maru of the Fisheries Agency (KY1804). Additional studies were carried out from the Japan Maritime Self–Defense Force icebreaker Shirase from the offshore slope to the front of the TIS in early March 2018 during the 59th Japanese Antarctic Research Expedition (JARE59) as well as in December 2019 and early March 2020 during the 61st Japanese Antarctic Research Expedition (JARE61).
Vertical profiles of temperature and salinity were measured with a conductivity–temperature–depth (CTD) probe (SBE 9plus, Sea–Bird Electronics, Bellevue, WA, USA from the Kaiyo–maru and SBE19, Sea–Bird Electronics, Bellevue, WA, USA from the Shirase ). In addition, seawater samples were taken to calibrate the salinity sensor. Seawater samples were collected vertically in rosette−mounted 10–L Niskin bottles (Ocean Test Equipment, Inc., Lauderdale, FL, USA) from the Kaiyo–maru and 4–L Niskin bottles (SBE55 ECO, Sea–Bird Electronics, Bellevue, WA, USA) from the shirase .
Seawater was subsampled into (1) a 200–mL glass vial (Maruemu Co., Ltd., Osaka, Japan) for measurement of dissolved inorganic carbon (DIC) and total alkalinity (TA), (2) a 15–mL glass screw–cap vial (Nichiden–Rika Glass Co. Ltd, Kobe, Japan) for measurement of the oxygen isotopic ratio (δ18O) of the water, (3) a 10–mL polyethylene screw–cap vial (Eiken Chemical Co. Ltd, Tokyo, Japan) for measurement of inorganic nutrients (NO3, PO43–, and Si(OH)4), and (4) a 300–mL Nalgene polycarbonate bottle (Thermo Fisher Scientific Inc., Waltham, MA, USA) for measurement of chlorophyll a (chl.a) concentrations.
The concentrations of DIC were determined by coulometry (Johnson et al., 1985, 1992) using a hand–made CO2 extraction system (Ono et al., 1998) and a coulometer (CM5012, UIC, Inc., Binghamton, NY, USA). The TA of the seawater was determined by titration (Dickson et al., 2007) with a TA analyzer (ATT–05, Kimoto Electric Co., Ltd., Japan). Both DIC and TA measurements were calibrated against reference seawater materials (Batch AO and AP; KANSO Technos Co., Ltd., Osaka, Japan) traceable to the certified reference material distributed by Prof. A. G. Dickson (Scripps Institution of Oceanography, La Jolla, CA, USA).
The seawater δ18O was determined with a mass spectrometer (Isoprime precisION, Elementar, Stockport, UK) with the equilibration bath of 30.0°C. The δ18O in permil (‰) was calculated using the 18O:16O ratio of Vienna standard mean ocean water (VSMOW2) as the standard.
The concentrations of NO3, PO43–, and Si(OH)4 in the seawater were determined in accord with the Joint Global Ocean Flux Study (JGOFS) spectrophotometric method (JGOFS, 1994) using auto–analyzer systems: a QuAAtro 2–HR system (BL–tec, Osaka, Japan) and a Seal Analytical system (Norderstadt, Germany). The analyzers were calibrated with reference materials for nutrient analysis (Lots AW and BG; KANSO Technos Co., Ltd.).
The concentrations of chl.a were determined with a fluorometer (Model 10AU, Turner Designs, Inc., Sunnyvale, CA, USA) by the method of Parsons et al. (1984). Standards (0.05–159 µg L–1 chl.a) prepared from a liquid chl.a standard (Wako Pure Chemical Industries, Ltd., Osaka, Japan) by stepwise dilution with N,N–dimethylformamide were used to calibrate the fluorometer before chl.a measurements.
Table S1. Dataset. “–” indicates no data.