Physical and biological properties of early winter Antarctic sea ice in the Ross Sea

Abstract

This work presents the results of physical and biological investigations at 27 biogeochemical stations of early winter sea ice in the Ross Sea during the 2017 PIPERS cruise. Only two similar cruises occurred in the past, in 1995 and 1998. The year 2017 was a specific year, in that ice growth in the Central Ross Sea was considerably delayed, compared to previous years. These conditions resulted in lower ice thicknesses and Chl-a burdens, as compared to those observed during the previous cruises. It also resulted in a different structure of the sympagic algal community, unusually dominated by Phaeocystis rather than diatoms. Compared to autumn-winter sea ice in the Weddell Sea (AWECS cruise), the 2017 Ross Sea pack ice displayed similar thickness distribution, but much lower snow cover and therefore nearly no flooding conditions. It is shown that contrasted dynamics of autumnal-winter sea-ice growth between the Weddell Sea and the Ross Sea impacted the development of the sympagic community. Mean/median ice Chl-a concentrations were 3–5 times lower at PIPERS, and the community status there appeared to be more mature (decaying?), based on Phaeopigments/Chl-a ratios. These contrasts are discussed in the light of temporal and spatial differences between the two cruises.

Sea-ice production and air/ice/ocean/biogeochemistry interactions in the Ross Sea during the PIPERS 2017 autumn field campaign

“…Tison and others (submitted, this issue) demonstrate how the peculiar sea-ice growth conditions in 2017 led to considerably lower Chl- a burdens compared to both the previous early winter cruises in the Ross Sea (1995, 1998) and to other early winter cruises elsewhere in the Antarctic (Tison and others, 2017). A change in the sympagic community structure towards Phaeocystis -dominated cell abundances was also observed in 2017 (instead of diatom-dominated assemblages as noted in earlier reports of, e.g.…”

“…Jeffries and Adolphs, 1997). Tison and others (submitted, this issue) provide additional details on sea-ice structural differences encountered in 1998 vs 2017.…”

“…However, the inferred active primary production observed in March 2017 in TNBP may have seeded some of the algal stocks observed in our biogeochemical ice samples acquired further north along Victoria Land. Tison and others (submitted, this issue) provide additional details on sea-ice structure and the physical and biological properties of the sea ice. Much of the biogeochemical data are still being processed and interpreted, with results forthcoming.…”

“…The biogeochemical component of PIPERS consisted of 27 sites along the cruise track where physical measurements were collected to support a suite of biogeochemical and ecological process studies focusing on major physical and environmental drivers (e.g. microbial production, nutrient recycling across the ocean/sea-ice/atmosphere interfaces, and gas exchange; see Tison and others, submitted, this issue). In addition to measurements at ice stations, zodiac-based measurements were acquired within the MIZ and coastal polynyas to capture biogeochemical processes during the first stages of sea-ice growth (i.e.…”

Validation of a daily satellite-derived Antarctic sea ice velocity product: impacts on ice kinematics

“…A weighted polynomial interpolator (Scargle, 1982;Heil et al, 2001) was applied to the quality-controlled position measurements to yield an equi-temporal hourly time series. In the Ross Sea, a total of eight position-only buoys 160 were deployed as part of the Polynyas, Ice Production, and seasonal Evolution in the Ross Sea (PIPERS) cruise during austral autumn of 2017 (Tison et al, 2020). Four were excluded due to coastal proximity, and another one due to a short time series.…”