POSTER SESSION 2
10:30–12:30, Tuesday, September 15
Poster Session | 1 | 2 | 3 | 4 | Schedule at a Glance
ABSTRACT 1360 | POSTER 50
A SACW FULL OF COLORS: EXPLORING THE BIO-OPTICAL VARIABILITY OF THE SUB SUPERFICIAL SOUTH ATLANTIC CENTRAL WATER IN THE ALCATRAZES ARCHIPELAGO
Vertical stratification imposes challenges for collecting and interpreting radiometric profiles, demanding accurate thermohaline characterization in shallow waters. Under coastal upwelling influence, an uncoupled vertical optical stratification may emerge by illumination and dilution of advecting subsurface plumes. These conditions are often reported at Alcatrazes Archipelago (24°06’07”S, 45°41’35”W) but are unobservable by satellite sensors. In this study, we investigated the influence of South Atlantic Central Water (SACW) mixing fractions on subsurface spectral signatures, using a custom Python-based software developed by A.P.P.Forgiarini. Profiles from a HyperPro-II radiometer allowed computing an Apparent Visible Wavelength (AVW) from vertical Lu/Ed spectra (400 and 600nm), a proxy for subsurface bio-optical variability. SACW mixing fractions derived from the mixture triangle method and CTD data. When SACW accounted for ≥75% of the mixture, AVW shifted to shorter wavelengths, consistent with oligotrophic upwelled water. As the SACW fraction decreased (75% to 55%), AVW depicted greener hues, indicating phytoplankton accumulation, while fractions <50% shifted the index back to blue, demonstrating sensitivity to biological responses to upwelled nutrients and complementing surface remote sensing. However, the AVW range was modest (481 to 499 nm). Most vertical profiles displayed blue surface and greener subsurface waters; the variability of AVW with depth suggested small-scale features that need further investigation. Ongoing analyses include the decoupling bioptical components’ signals using derivative analyses and multivariate clustering to understand the biogeochemical impacts of upwelling events in this important conservation area and to improve the interpretation of vertically structured optical signals in coastal systems.
Aurea Ciotti, Center for Marine Biology USP, [email protected], https://orcid.org/0000-0001-7163-8819
Ana Paula Piazza Forgiarini, Center for Marine Biology USP, [email protected], https://orcid.org/0000-0002-8340-7855
Ana Laura Tribst-Corrêa, Center for Marine Biology USP, [email protected], https://orcid.org/0000-0002-6641–0585
Poster Session | 1 | 2 | 3 | 4 | Schedule at a Glance
