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Abstract The Ross Sea is known for showing the greatest sea-ice increase, as observed globally, particularly from 1979 to 2015. However, corresponding changes in sea-ice thickness and production in the Ross Sea are not known, nor how these changes have impacted water masses, carbon fluxes, biogeochemical processes and availability of micronutrients. The PIPERS project sought to address these questions during an autumn ship campaign in 2017 and two spring airborne campaigns in 2016 and 2017. PIPERS used a multidisciplinary approach of manned and autonomous platforms to study the coupled air/ice/ocean/biogeochemical interactions during autumn and related those to spring conditions. Unexpectedly, the Ross Sea experienced record low sea ice in spring 2016 and autumn 2017. The delayed ice advance in 2017 contributed to (1) increased ice production and export in coastal polynyas, (2) thinner snow and ice cover in the central pack, (3) lower sea-ice Chl- a burdens and differences in sympagic communities, (4) sustained ocean heat flux delaying ice thickening and (5) a melting, anomalously southward ice edge persisting into winter. Despite these impacts, airborne observations in spring 2017 suggest that winter ice production over the continental shelf was likely not anomalous.
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The Regulation of Sea Ice Thickness by Double‐Diffusive Processes in the Ross Gyre
Abstract New fine‐scale observations from the central Ross Gyre reveal the presence of double‐diffusive staircase structures underlying the surface mixed layer. These structures are persistent over seasons, with more developed mixed layers within the double‐diffusive staircase in winter months. The sensitivity of the ice formation rate with respect to mixing processes within the main pycnocline (double‐diffusive versus purely turbulent mixing) is investigated with the 1‐D model. A scenario with purely turbulent mixing results in significant underestimates of sea ice thickness. However, a scenario when double‐diffusive mixing operates in the presence of weak shear yields plausible ranges for sea ice thickness that agrees well with the observations. The model results and observations suggest a peculiar feedback mechanism that promotes the self‐maintenance of double‐diffusive staircases. Suppression of the vertical heat fluxes due to the presence of a double‐diffusive staircase, compared to purely turbulent case, allows Upper Circumpolar Deep Water to be more exposed to surface buoyancy fluxes. Our results shed light on the process—double diffusion—that might account for estimated rates of winter water mass transformation in the central Ross Gyre.
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- Award ID(s):
- 1658479
- PAR ID:
- 10454327
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Oceans
- Volume:
- 124
- Issue:
- 10
- ISSN:
- 2169-9275
- Page Range / eLocation ID:
- p. 7068-7081
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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