Drivers of marine CO2-carbonate chemistry in the northern Antarctic Peninsula

Abstract

The Bransfield Strait is a climate change hotspot at the tip of the northern Antarctic Peninsula (NAP). The region is marked by a mixture of relatively warm waters from the Bellingshausen Sea with cold shelf waters from the Weddell Sea. Additionally, its deep central basin (>800 m) preserves seawater properties from the north-western Weddell Sea continental shelf. This study assessed long-term changes in carbonate chemistry in the Bransfield Strait and found that the hydrographic setting (i.e., a mixture between modified-Circumpolar Deep Water with Dense Shelf Water [DSW]) drives temporal variability of carbonate parameters. The western basin has experienced decreases in pH (seawater scale) over the last three decades (1996–2019), varying from −0.003 to −0.017 pH units yr⁻¹, while Ω_ar decreased from −0.01 to −0.07 yr⁻¹ throughout the water column. The central basin was characterized by a high contribution of DSW with high carbon dioxide (CO₂) content and the decomposition of organic matter produced and transported into its deep layer. With lower variability for all carbonate system variables, the eastern basin was likely regulated by internal mixing. Overall, the entire strait is almost reaching a CO₂-saturated condition, highlighting how sensitive subpolar regions are to the effects of human-induced climate change.

Key Points

The western basin experiences steeper pH decreases than the surrounding areas at a rate of −0.017 pH_sws units yr⁻¹ due to Circumpolar Deep Water intrusions
Dense Shelf Water inflow into the deep layer of the central basin promoted a CT increase of about 50 μmol kg⁻¹ in the 2010s relative to the 2000s
Internal mixing has likely reduced spatiotemporal variability of carbonate chemistry in the eastern basin since the 1990s

Santos-Andrade M., Kerr R., Orselli I. B. M., Monteiro T., Mata M. M. & Goyet C., 2023. Drivers of marine CO2-carbonate chemistry in the northern Antarctic Peninsula. Global Biogeochemical Cycles 37: e2022GB007518. doi: 10.1029/2022GB007518. Article (subscription required).

Ocean Acidification