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Abstract. During katabatic wind events in the Terra Nova Bay and Ross Sea polynyas, wind speeds exceeded 20 m s−1, air temperatures were below −25 ℃, and the mixed layer extended as deep as 600 meters. Yet, upper ocean temperature and salinity profiles were not perfectly homogeneous, as would be expected with vigorous convective heat loss. Instead, the profiles revealed bulges of warm and salty water directly beneath the ocean surface and extending downwards tens of meters. Considering both the colder air above and colder water below, we suggest the increase in temperature and salinity reflects latent heat and salt release during unconsolidated frazil ice production within the upper water column. We use a simplified salt budget to analyze these anomalies to estimate in-situ frazil ice concentration between 332 × 10−3 and 24.4 × 10−3 kg m−3. Contemporaneous estimates of vertical mixing by turbulent kinetic energy dissipation reveal rapid convection in these unstable density profiles, and mixing lifetimes from 2 to 12 minutes. The corresponding median rate of ice production is 26 cm day−1 and compares well with previous empirical and model estimates. Our individual estimates of ice production up to 378 cm day−1 reveal the intensity of short-term ice production events during the windiest episodes of our occupation of Terra Nova Bay Polynya. How to cite: De Pace, L., Smith, M., Thomson, J., Stammerjohn, S., Ackley, S., and Loose, B.: Frazil ice growth and production during katabatic wind events in the Ross Sea, Antarctica, The Cryosphere Discuss., https://doi.org/10.5194/tc-2019-213, in review, 2019.
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Transiting consolidated ice strongly influenced polynya area during a shrink event in Terra Nova Bay in 2013
Abstract Coastal polynyas in Antarctica are a window of air-sea energy exchange and an important source of Antarctic Bottom Water production. However, the relationship between the polynya area variation and the surrounding marine environment is yet to be fully understood. Here we quantify the influence of the volume of transiting consolidated ice on the Terra Nova Bay Polynya area with ice thickness data. Changes in transiting consolidated ice volume are shown to dominate the evolution and variation of the polynya during a typical polynya shrinking event that occurred between 19 June to 03 July, 2013, rather than katabatic winds or air temperature, which are commonly assumed to be the main drivers. Over the cold seasons from 2013 to 2020, the Terra Nova Bay Polynya area is highly correlated to the transiting consolidated ice volume. We demonstrate that thick transiting ice limits the polynya area by blocking the newly-formed sea ice from leaving.
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- Award ID(s):
- 1936222
- PAR ID:
- 10433982
- Date Published:
- Journal Name:
- Communications Earth & Environment
- Volume:
- 4
- Issue:
- 1
- ISSN:
- 2662-4435
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1038/s43247-023-00712-w
