Effects of Snow and Remineralization Processes on Nutrient Distributions in Multi-Year Antarctic Landfast Sea Ice

We elucidated the effects of snow and remineralization processes on nutrient distributions in multi-year landfast sea ice (fast ice) in Lutzow-Holm Bay, East Antarctica. Based on sea-ice salinity, oxygen isotopic ratios, and thin section analyses, we found that the multi-year fast ice grew upward due to the year-by-year accumulation of snow. Compared to ice of seawater origin, nutrient concentrations in shallow fast ice were low due to replacement by clean and fresh snow. In deeper ice of seawater origin (the lower half of the multi-year fast ice column), remineralization was dominated by the degradation of organic matter. By comparison between first- and muti-year ice, the biological uptake and the remineralization were dominated in relatively young ice and older ice, respectively, under the physical process of brine drainage

Biogeochemical characteristics of brash sea ice and icebergs during summer and autumn in the Indian sector of the Southern Ocean

We analyzed biogeochemical components of brash ice, originating from sea ice and icebergs, collected in the Indian sector of the Southern Ocean during the summer and autumn of 2018–2020. Ice samples, collected from seawater by net or cage methods, were melted in the dark under cool conditions to measure physical and biogeochemical components such as salinity, stable oxygen isotopes, nutrients, and chlorophyll-a. We compared brash ice parameters with those of seawater samples from the temperature minimum layer, corresponding to the water in which the sea ice originated, to examine the effects of processes such as brine drainage, snow-ice formation, and biological activities on the biogeochemical components in sea ice. Samples from icebergs (ice formed on land) had salinity of zero and low concentrations of all other components, suggesting that the atmospheric deposition of nutrients is minimal in this clean environment. However, sea ice samples had a wide range of values for each parameter. Our results show that meteoric water makes a smaller contribution to sea ice than it typically does to multi-year landfast ice, and there is no correlation between this meteoric water contribution and nutrient concentrations, which suggests that the contribution of snow-ice formation to nutrients within sea ice is subordinate to the role of biological processes. Nutrient and chlorophyll-a concentrations in our brash ice samples are of similar magnitude to those in sea ice samples collected in the same area by coring of thick pack ice. Our data represent end-member values that may be useful to estimate the respective contributions of snow, sea ice, and seawater to surface water samples

Atmosphere-sea ice-ocean interaction study in Saroma-ko Lagoon, Hokkaido, Japan 2021

An atmosphere-sea ice-ocean interaction study was conducted at the Saroma-ko Lagoon, Hokkaido, Japan from 27 February to 9 March 2021. Air-sea ice CO2 flux measurements were conducted by eddy covariance and chamber methods together with meteorological observations. Sea ice cores were collected to understand the interaction between the atmosphere and under-ice water with respect to fluxes of heat and biogeochemical components. Physical and biogeochemical parameters such as temperature, salinity, ice structure. environmental DNA, and concentrations of gases, nutrients, and trace metals were measured. Under-ice water properties were monitored to quantify heat budgets and interactions with sea ice biogeochemical properties. Incubation experiments with ice algae were conducted. Equipment such as air sea ice CO2/CH4 flux chambers, an eddy covariance system, a trace metal analyzer, and a pump and sampler for environmental DNA were tested and compared to prepare for future Arctic and Antarctic expeditions. In addition. movies and pictures were taken under the auspices of the educational program of Hokkaido University (LASBOS) to enhance educational programs in ocean science. The field campaign activities provided useful information for inter-comparison research and future studies of sea ice in polar oceans