Freshwater flux from ice sheet melting and iceberg calving in the Southern Ocean

Hammond, Mark; Harle, James

doi:10.1002/gdj3.43

Cited by 15 publications

(18 citation statements)

References 14 publications

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“…Also, the missing density gradients due to the absence of ice shelves and freshwater imply that some of the heat that is available on the continental slope but is not brought onto the shelf in this simulation might be if ice shelves were introduced, since their effect on the circulation can be substantial (e.g., Dinniman et al, ; Jourdain et al, ; St‐Laurent et al, ). In a future contribution, we will compare our present results with a global eddy‐resolving POP/CICE simulation (1–2‐km resolution on the Antarctic continental margin) with climatological freshwater fluxes of ice‐shelf melting and iceberg calving derived from observations (Hammond & Jones, ).…”

Section: The Global 01∘ Pop Simulationmentioning

confidence: 94%

Oceanic Heat Delivery to the Antarctic Continental Shelf: Large‐Scale, Low‐Frequency Variability

2018

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Onshore penetration of oceanic water across the Antarctic continental slope (ACS) plays a major role in global sea level rise by delivering heat to the Antarctic marginal seas, thus contributing to the basal melting of ice shelves. Here the time‐mean (Φmean) and eddy (Φeddy) components of the heat transport (Φ) across the 1,000‐m isobath along the entire ACS are investigated using a 0.1∘ global coupled ocean/sea ice simulation based on the Los Alamos Parallel Ocean Program (POP) and sea ice (Community Ice CodE) models. Comparison with in situ hydrography shows that the model successfully represents the basic water mass structure, with a warm bias in the Circumpolar Deep Water layer. Segments of on‐shelf Φ, with lengths of O(100–1,000 km), are found along the ACS. The circumpolar integral of the annually averaged Φ is O(20 TW), with Φeddy always on‐shelf, while Φmean fluctuates between on‐shelf and off‐shelf. Stirring along isoneutral surfaces is often the dominant process by which eddies transport heat across the ACS, but advection of heat by both mean flow‐topography interactions and eddies can also be significant depending on the along‐ and across‐slope location. The seasonal and interannual variability of the circumpolarly integrated Φmean is controlled by convergence of Ekman transport within the ACS. Prominent warming features at the bottom of the continental shelf (consistent with observed temperature trends) are found both during high‐Southern Annular Mode and high‐Niño 3.4 periods, suggesting that climate modes can modulate the heat transfer from the Southern Ocean to the ACS across the entire Antarctic margin.

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Section: The Global 01∘ Pop Simulationmentioning

confidence: 94%

Oceanic Heat Delivery to the Antarctic Continental Shelf: Large‐Scale, Low‐Frequency Variability

2018

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“…The prescribed open boundary conditions at the equator are derived from HYCOM (http://hycom.org). River runoff comes from the product of Dai and Trenberth [2002] augmented with an estimate of Antarctic continental runoff produced by Hammond and Jones [2016]. Tidal forcing is not included.…”

Section: Physical Model Configurationmentioning

confidence: 99%

A data assimilating model for estimating Southern Ocean biogeochemistry

2017

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A Biogeochemical Southern Ocean State Estimate (B‐SOSE) is introduced that includes carbon and oxygen fields as well as nutrient cycles. The state estimate is constrained with observations while maintaining closed budgets and obeying dynamical and thermodynamic balances. Observations from profiling floats, shipboard data, underway measurements, and satellites are used for assimilation. The years 2008–2012 are chosen due to the relative abundance of oxygen observations from Argo floats during this time. The skill of the state estimate at fitting the data is assessed. The agreement is best for fields that are constrained with the most observations, such as surface pCO2 in Drake Passage (44% of the variance captured) and oxygen profiles (over 60% of the variance captured at 200 and 1000 m). The validity of adjoint method optimization for coupled physical‐biogeochemical state estimation is demonstrated with a series of gradient check experiments. The method is shown to be mature and ready to synthesize in situ biogeochemical observations as they become more available. Documenting the B‐SOSE configuration and diagnosing the strengths and weaknesses of the solution informs usage of this product as both a climate baseline and as a way to test hypotheses. Transport of Intermediate Waters across 32°S supplies significant amounts of nitrate to the Atlantic Ocean (5.57 ± 2.94 Tmol yr−1) and Indian Ocean (5.09 ± 3.06 Tmol yr−1), but much less nitrate reaches the Pacific Ocean (1.78 ± 1.91 Tmol yr−1). Estimates of air‐sea carbon dioxide fluxes south of 50°S suggest a mean uptake of 0.18 Pg C/yr for the time period analyzed.

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“…Through the adjoint method, the atmospheric state is then adjusted to better fit the observations. River and Antarctic discharges are implemented using the freshwater continental runoff mixed product of Dai and Trenberth [] and an estimated distributed Antarctic discharge from Hammond and Jones []. To represent ice dynamics and thermodynamics, an ice component, formulated in Losch et al .…”

Section: Methodsmentioning

confidence: 99%

Space and time variability of the Southern Ocean carbon budget

et al. 2017

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The upper ocean dissolved inorganic carbon (DIC) concentration is regulated by advective and diffusive transport divergence, biological processes, freshwater, and air‐sea CO2 fluxes. The relative importance of these mechanisms in the Southern Ocean is uncertain, as year‐round observations in this area have been limited. We use a novel physical‐biogeochemical state estimate of the Southern Ocean to construct a closed DIC budget of the top 650 m and investigate the spatial and temporal variability of the different components of the carbon system. The dominant mechanisms of variability in upper ocean DIC depend on location and time and space scales considered. Advective transport is the most influential mechanism and governs the local DIC budget across the 10 day–5 year timescales analyzed. Diffusive effects are nearly negligible. The large‐scale transport structure is primarily set by upwelling and downwelling, though both the lateral ageostrophic and geostrophic transports are significant. In the Antarctic Circumpolar Current, the carbon budget components are also influenced by the presence of topography and biological hot spots. In the subtropics, evaporation and air‐sea CO2 flux primarily balances the sink due to biological production and advective transport. Finally, in the subpolar region sea ice processes, which change the seawater volume and thus the DIC concentration, compensate the large impact of the advective transport and modulate the timing of biological activity and air‐sea CO2 flux.

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Freshwater flux from ice sheet melting and iceberg calving in the Southern Ocean

Cited by 15 publications

References 14 publications

Oceanic Heat Delivery to the Antarctic Continental Shelf: Large‐Scale, Low‐Frequency Variability

Oceanic Heat Delivery to the Antarctic Continental Shelf: Large‐Scale, Low‐Frequency Variability

A data assimilating model for estimating Southern Ocean biogeochemistry

Space and time variability of the Southern Ocean carbon budget

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