Abstract
AbstractIn cold polar waters, temperatures sometimes drop below the freezing point, a process referred to as supercooling. However, observational challenges in polar regions limit our understanding of the spatial and temporal extent of this phenomenon. We here provide observational evidence that supercooled waters are much more widespread in the seasonally ice‐covered Southern Ocean than previously reported. In 5.8% of all analyzed hydrographic profiles south of 55°S, we find temperatures below the surface freezing point (“potential” supercooling), and half of these have temperatures below the local freezing point (“in situ” supercooling). Their occurrence doubles when neglecting measurement uncertainties. We attribute deep coastal‐ocean supercooling to melting of Antarctic ice shelves and surface‐induced supercooling in the seasonal sea‐ice region to wintertime sea‐ice formation. The latter supercooling type can extend down to the permanent pycnocline due to convective sinking plumes—an important mechanism for vertical tracer transport and water‐mass structure in the polar ocean.
Highlights
Supercooled water, that is, water with a temperature below a reference freezing point temperature, has been observed in the polar oceans of the Arctic (e.g., Drucker et al, 2003; Katlein et al, 2020; Skogseth et al, 2009) and Antarctic (e.g., Brett et al, 2020; Countryman, 1970; Lewis & Perkin, 1986)
Almost half of the profiles with potential supercooling show in situ supercooling (Figure 2f)
While their fraction and spatial patterns might be influenced by spatio‐temporal sampling biases, our analysis demonstrates that potential and in situ supercooling are much more widespread in the Southern Ocean than had been found in previous, more regionally limited, observations
Summary
Supercooled water, that is, water with a temperature below a reference freezing point temperature, has been observed in the polar oceans of the Arctic (e.g., Drucker et al, 2003; Katlein et al, 2020; Skogseth et al, 2009) and Antarctic (e.g., Brett et al, 2020; Countryman, 1970; Lewis & Perkin, 1986). Hydrographic data collected by autonomous profiling floats with an ice‐avoidance algorithm (Riser et al, 2018; Wong & Riser, 2011) and instrumented marine animals (Roquet et al, 2013, 2014; Treasure et al, 2017) provide an opportunity to detect supercooled waters year‐ round (supporting information Figure S1). Using these data to supplement traditional ship‐based HAUMANN ET AL
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call