Download Impact of ocean stratification on small

Impact of ocean stratification on small-scale physical oases for pelagic life
Daniel Grados1,2, Ronan Fablet3, Francois Colas2,4, Alexis Chaigneau5, Vincent Echevin4, Gary
Vargas6, Ramiro Castillo2 and Arnaud Bertrand1,6,7
Universidade Federal de Pernambuco – Departamento de Oceanografia (UFPE-DOCEAN), Recife,
Brazil. [email protected]
2
Instituto del Mar del Perú (IMARPE), Lima, Perú
3
TELECOM Bretagne, UMR CNRS-3192-Lab-STICC, Brest, France
4
IRD-CNRS-Sorbonne Universite ́s (UPMC Univ. Paris 6)-MNHN, LOCEAN/IPSL Laboratory, Paris,
France
5
IRD, UMR LEGOS, CNES/CNRS/IRD/UPS, Tulouse, France
6
Universidade Federal Rural de Pernanbuco (UFRPE), Recife, Brazil.
7
Institut de Recherche pour le Développement, UMR MARBEC, Sète, France
1
Physical forcing of the surface ocean includes a variety of energetic processes, ranging from internal
wave (IW) to submesoscale and mesoscale. Recent works based on acoustic data showed that, off Peru,
the vertical displacements of the oxycline depth provide a robust proxy of isopycnals displacements
over a wide range of horizontal scales. These studies revealed the importance of ephemeral hotspots
(oases), which concentrate organisms ranging from zooplankton to seabirds, enhancing trophic
interactions. Here, we address the question of the potential impact of climate variability on these finescale oases for life. Indeed, temperature and salinity changes induced by climate change are expected to
lead to an ocean near-surface stratification increase that could have a negative impact on the intensity
of physical small-scale structures and, consequently, on patterns distribution of marine life. For that we
use 35 000 physical structures from acoustic data collected during twelve scientific surveys conducted
between 2002 and 2011 off Peru. We estimate the strength of these structures, its power of aggregation
on zooplankton and small pelagic fish and also ocean stratification conditions. Results show that higher
the ocean stratification, less the strength and the power of aggregation of the fine scale physical
structures. Climate variability, and potentially climate change, could thus lead to a reduction of the size
and density of organisms patches with a potential impact on consequent trophic interactions.