TErra NOva bay polynya high Resolution Experiment

The impact of polynyas on the polar oceans is known to be relevant for physical and ecological aspects; in particular, the air–sea heat exchange is 1 or 2 orders of magnitude greater than through the surrounding sea ice. In latent heat polynyas, such as Terra Nova Bay (TNB) polynya, the intense heat loss leads to rapid and persistent ice growth and the brine rejected increases the salinity of the subsurface waters, resulting in the production of High Salinity Shelf Water (HSSW) [Kurtz & Bromwich, 1983; Jacobs et al., 1985; Budillon & Spezie, 2000; Fusco et al., 2002] that contributes to the Antarctic Bottom Water (AABW) formation [Orsi et al., 1999].

In recent decades, AABW has warmed, freshened and reduced in volume and Ross Sea Bottom Water (RSBW), the second largest source of AABW, has experienced the largest freshening. This freshening has been linked to a decrease in salinity of HSSW, which freshened by 0.05 dec⁻¹ in TNB between 1995 and 2006 [Jacobs et al., 2002; Jacobs & Giulivi, 2010; Fusco et al., 2009; Budillon et al., 2011]. Recently, an analysis on long-term mooring data collected in the TNB show that after a decrease between 1995 and 2014, HSSW salinity rebounded sharply after 2014, with values in 2018 similar to those observed in the mid-late 1990s [Castagno et al., 2019]. The increase in salinity after 2014 may be the most recent expression of the interannual variability evident in the HSSW salinity record, but the time series is too short to draw firm conclusions. This evidence highlights the need of additional in situ measurements and studies for understanding the forcing that influence TNB HSSW salinity formation and variability.

In this context, the research activities planned in the framework of the TENORE project aim to improve the current knowledge of the TNB polynya, expanding the classical in situ measurement capabilities towards a hierarchical multiplatform approach that could provide a more complete and detailed understanding of the physical and biochemical processes observed during late summer - winter transition, their local and regional balance, and their role in the complex feedback between ocean and atmosphere in the climate change scenario.