Sea ice formation, glacial melt and the solubility pump boundary conditions in the Ross Sea

Abstract

1. Noble gas tracers can infer the rate of sea ice production in polynyas. 2. Frazil ice in polynyas appears to block air-sea gas exchange mechanisms. 3. The solubility pump is influenced by glacial ice melt and sea ice formation. Hosted fileessoar.10512535.1.docx available at https://authorea.com/users/542520/articles/600977-seaice-formation-glacial-melt-and-the-solubility-pump-boundary-conditions-in-the-ross-sea Sea ice formation, glacial melt and the solubility pump boundary conditions in the Ross Sea.

Seasonal Dynamics of Dissolved Iron on the Antarctic Continental Shelf: Late‐Fall Observations From the Terra Nova Bay and Ross Ice Shelf Polynyas

“…Surface mixed layers were relatively shallow, ranging from a maximum of ∼300 m in the west to less than 100 m in the east, suggesting that the less extreme weather we experienced was more typical of this area before sampling, rather than the intense katabatic wind events that we observed impacting the Terra Nova Bay region. The main water masses identified from the hydrographic data in Figure 8 again follow the classification of Orsi and Wiederwohl (2009), and include MCDW (28.0 < $${{\gamma}}^{n}$$ < 28.27 kg m −3 , T < 0°C) over the upper water column at stations 14, 15, and 18; AASW ($${{\gamma}}^{n}$$ < 28.0 kg m −3 ), which was present at stations 16 and 17; and SW ($${{\gamma}}^{n}$$ > 28.27 kg m −3 , potential temperature < −1.85°C), which was observed below depths ranging from ∼100 to ∼400 m. Also observed was an intrusion of Ice Shelf Water (ISW) centered in the 450–500 m depth range at stations 16 and 17 (Figure 8b), as indicated by potential temperatures below −1.95°C, and by saturation anomalies in helium and neon (which are enriched in glacial meltwaters) in samples collected at a nearby CTD station (Loose et al., 2022). The ISW is thought to be formed through the interaction of SW with the glacial ice shelf, and has been previously observed north of the Ross Ice Shelf near the 180° meridian (Jacobs & Giulivi, 1985; Orsi & Wiederwohl, 2009; Smethie & Jacobs, 2005).…”

“…The DFe profiles from stations 3, 4, 5, and 7 show concentration maxima of ∼0.5–1 nM at various depths between 100 and 500 m (Figure 5 ), which may reflect advective inputs from nearshore waters or near‐bottom waters over adjacent shallow banks, where DFe concentrations are typically elevated (e.g., Grotti et al., 2001 ; Marsay et al., 2014 , 2017 ). In addition, the elevated near‐surface DFe concentrations at station 5 may reflect processes associated with sea ice formation, as indicated by the excess xenon and krypton (which are excluded during sea ice formation) and deficit in helium (which is preferentially incorporated in sea ice) measured in surface samples collected from a nearby station using the ship's conventional CTD‐rosette (Loose et al., 2022 ). Other potential sources of DFe at these depths are the remineralization of organic matter vertically exported from the preceding growing season (DeJong et al., 2017 ; Giordano et al., 2020 ), and glacial meltwaters (Annett et al., 2015 ; McGillicuddy et al., 2015 ), although with regard to glacial inputs we see no clear evidence that elevated DFe concentrations are associated with intrusions of TISW (Figure 5 ).…”

“…The ISW is thought to be formed through the interaction of SW with the glacial ice shelf, and has been previously observed north of the Ross Ice Shelf near the 180° meridian (Jacobs & Giulivi, 1985 ; Orsi & Wiederwohl, 2009 ; Smethie & Jacobs, 2005 ). Saturation anomalies in dissolved helium and neon in samples collected along the Ross Ice Shelf section suggest glacial meltwater contributions of up to ∼1% (Loose et al., 2022 ).…”

“…In addition to the trace‐metal CTD‐rosette sampling, hydrographic data and water‐column samples for analysis of other species (e.g., oxygen and noble gases; see Ackley et al., 2020 ; Loose et al., 2022 ) were collected using the ship's conventional CTD‐rosette which was fitted with 12‐L Ocean Test Equipment samplers. However, the conventional CTD‐rosette sampling stations were not always located adjacent to the trace‐metal CTD‐rosette stations, which limits our ability to directly compare data sets from the different sampling systems.…”

Constraining Physical Gas Exchange Processes and Transient Tracer Saturations in the Arctic Ocean using Noble Gas

“…We have compared multiple Arctic Ocean gas exchange models (based on similar models used in the Antarctic by Loose et al [3] and in the Labrador Sea by Hamme et al [4]) to constrain the fractions of Arctic water composed of Pacific, Atlantic and sea ice melt-derived origin waters, as well as the amount of sea ice being formed and air being injected into the water via bubbles. These parameters are estimated using a χ 2 -minimisation procedure, where the misfit between fitted parameters and data is minimised.…”