Sea Ice Formation, Glacial Melt and the Solubility Pump Boundary Conditions in the Ross Sea

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Loose, Brice, Stammerjohn, Sharon, Sedwick, Peter, Ackley, Stephen
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: ODU Digital Commons 2023
• Subjects: Air bubbles; Air/sea exchange; Antarctic bottom water; Argon; Atmospheric gases; Bottom water; Boundary conditions; Carbon dioxide; Climate change; Cryopumping; Deep sea; Dense shelf water; Dense water; Evaporation; Frazil ice; Gas exchange; Gases; Glacier melting; Glaciers; Heat loss; Helium; Ice formation; Ice melting; Katabatic winds; Krypton; Meltwater; Neon; Noble gases; Ocean surface; Oceans; Oxygen; Polynya; Polynyas; Rare gases; Sea ice; Sea ice formation; Sea ice types; Seawater; Slurries; Solubility; Solubility pump; Uptake; Ventilation; Wind; Winds; Xenon; Environmental Indicators and Impact Assessment; Oceanography; Oceanography and Atmospheric Sciences and Meteorology; Antarctic; Ross Sea; Terra Nova Bay; Antarc*
• Online Access: https://digitalcommons.odu.edu/oeas_fac_pubs/486; https://doi.org/10.1029/2022JC019322; https://digitalcommons.odu.edu/context/oeas_fac_pubs/article/1497/viewcontent/Sedwick_2023_SeaIceFormationGlacialMeltandtheOCR.pdf

Seasonal formation of Dense Shelf Water (DSW) in the Ross Sea is a direct precursor to Antarctic Bottom Water, which fills the deep ocean with atmospheric gases in what composes the southern limb of the solubility pump. Measurements of seawater noble gas concentrations during katabatic wind events in two Ross Sea polynyas reveal the physical processes that determine the boundary value properties for DSW. This decomposition reveals 5–6 g kg−1 of glacial meltwater in DSW and sea-ice production rates of up to 14 m yr−1 within the Terra Nova Bay polynya. Despite winds upwards of 35 m s−1 during the observations, air bubble injection had a minimal contribution to gas exchange, accounting for less than 0.01 μmols kg−1 of argon in seawater. This suggests the slurry of frazil ice and seawater at the polynya surface inhibits air-sea exchange. Most noteworthy is the revelation that sea-ice formation and glacial melt contribute significantly to the ventilation of DSW, restoring 10% of the gas deficit for krypton, 24% for argon, and 131% for neon, while diffusive gas exchange contributes the remainder. These measurements reveal a cryogenic component to the solubility pump and demonstrate that while sea ice blocks air-sea exchange, sea ice formation and glacial melt partially offset this effect via addition of gases. While polynyas are a small surface area, they represent an important ventilation site within the southern-overturning cell, suggesting that ice processes both enhance and hinder the solubility pump.