Projected West Antarctic Ocean Warming Caused by an Expansion of the Ross Gyre

Abstract

The cyclonic Ross Gyre (RG) occupies the south-west Pacific sector of the Southern Ocean (Figure 1a). Evidence from hydrographic data (Gouretski, 1999), satellite altimetry (Dotto et al., 2018), and modeling (Rickard et al., 2010) suggests the RG extends more than 3,000 m below the ocean surface, with a transport of ∼20 Sv, dominating the large-scale thermohaline structure of the Ross Sea (RS). The horizontal RG extent is limited by the continental shelf break to the south and the Pacific-Antarctic Ridge (PAR) to the north and west (Figure 1a). The southward-flowing eastern limb of the RG is much less strongly constrained by topography (Patmore et al., 2019) and its location is more variable (Dotto et al., 2018;Sokolov & Rintoul, 2009). The eastern RG limb, and the adjacent Antarctic Circumpolar Current (ACC), supply warm Circumpolar Deep Water (CDW) to the Amundsen Sea (AS) shelf (Jenkins et al., 2016;Nakayama et al., 2018) that supports rapid melting when it reaches ice shelf cavities. Increases in such ocean-driven melting are known to be causing thinning of the ice sheet in the nearby Amundsen-Bellingshausen Seas (Depoorter et al., 2013;Jenkins et al., 2016).Satellite altimetry reveals variability in the RG strength and the eastern RG boundary position (Armitage et al., 2018;Dotto et al., 2018;Sokolov & Rintoul, 2009); whereas, numerical experiments have shown that the RG variability influences the water masses along the AS shelf (Nakayama et al., 2018). Any changes in the circulation of this region may be of wide importance, considering the ocean-driven ice loss from West Antarctica during recent decades (Paolo et al., 2015) and the consequences for global sea-level rise (Shepherd et al., 2018).We use numerical simulations of the United Kingdom Earth System Model (UKESM1) implementation for the Coupled Model Intercomparison Project 6 (CMIP6) (Sellar et al., 2020) to analyze the RG dynamics and its effects on the Amundsen and Bellingshausen seas. We consider historical simulations and two contrasting future climate scenarios associated with the Shared Socioeconomic Pathways SSP1-1.9 and SSP5-8.5 (Riahi et al., 2017).

Future Response of Antarctic Continental Shelf Temperatures to Ice Shelf Basal Melting and Calving

“…(2018). While HadGEM3‐GC3.1‐LL cannot produce the “V” shaped isopycnals characteristic of “dense” regimes, it does produce a “cool” (Moorman et al., 2020) Western Ross Sea, which is most similar to “dense.” The Ross Gyre is reproduced well in UKESM1 (Gómez‐Valdivia et al., 2023)—for which HadGEM3‐GC3.1‐LL is the physical core (Sellar et al., 2019)—and sea‐ice area is captured within observational uncertainty (Roach et al., 2020). HadGEM3‐GC3.1‐LL is therefore a reasonable model to explore the freshening response.…”

Impact of Ross Gyre on surface circulation in the Amundsen Sea, Antarctica

“…Surface circulation also alters the ice motion (Dewey et al 2018). Surface circulation study is fundamental in the Amundsen Sea (Gordon 1988, Dotto et al 2018, Nakayama et al 2018, Gómez-Valdivia et al 2023.…”

Temperature-enhanced effects of iron on Southern Ocean phytoplankton

“…The temperature was enhanced by 2 °C, based on forecasts from the IPCC report (Meredith et al, 2019). Whilst the Amundsen Sea has shown a warming trend over the past years already (Gómez-Valdivia et al, 2023;Drijfhout et al, 2024), the surface waters of the Weddell Sea might not increase as much with climate change, but show short-term local temperature increases (Darelius et al, 2023;Morrison et al, 2023;Teske et al, 2024). The concentration of dFe in the Fe addition treatments (F and TF) was increased by 2 nM.…”