Figure 9. Seasonal variation in weighted GHG contributions with Global
Warming Potential (GWP) for time horizons of 20 (GWP20)
and 100 (GWP100) years
The pronounced seasonal gradients in outgassing observed around the
major upwelling cells are intimately linked to both seasonal and spatial
variabilities in SST. This relationship is influenced by the interplay
between SST and gas concentrations at the sea-air interface. The
solubility of dissolved gases decreases with rising SST, further
intensified by upwelling-driven transport of gases into the mixed layer,
creating concentration gradients at the sea-air interface. Additionally,
varying seasonal wind stress intensities and the ventilation of older
mesopelagic water along the coast contribute significantly to the
enhancement of outgassing. Biological processes further play a role in
this complex dynamic (e.g. Frame et al., 2014; Sabbaghzadeh et al.,
2021). Previous field studies have supported the notion of upwelling
control on outgassing (e.g. Rehder et al., 2002; Nevison et al., 2004).
These studies demonstrated significant correlations between SST,
upwelling-favorable winds, and sea surface gas concentrations, providing
empirical evidence that strengthens the association between upwelling
and increased outgassing. The most upwelling-favorable winds occur in
the BUS between 14°S and 35°S, where coastal topography and shelf width
result in independent cells with enhanced upwelling (e.g. Lutjeharms &
Meeuvis ,1987; Hutchings et al., 2009).