ALBERT

Description: Reloca Slide is the relict of an ~24 km³ submarine slope collapse at the base of the convergent continental margin of central Chile. Bathymetric and seismic data show that directly to the north and south of the slide the lower continental slope is steep (~10°), the deformation front is shifted landwards by 10–15 km, and the frontal accretionary prism is uplifted. In contrast, ~80 km to the north the lower continental margin presents a lower slope angle of about 4° and a wide frontal accretionary prism. We propose that high effective basal friction conditions at the base of the accretionary prism favored basal accretion of sediment and over-steepening of the continental slope, producing massive submarine mass wasting in the Reloca region. This area also spatially correlates with a zone of low coseismic slip of the 2010 Maule megathrust earthquake, which is consistent with high basal frictional coefficients. This article is protected by copyright. All rights reserved.

Description: [1]  Observations of gas-phase iodine species were made during a field campaign in the Eastern Pacific marine boundary layer (MBL). The Climate and HAlogen Reactivity tropicaL EXperiment (CHARLEX) in the Galápagos Islands, running from September 2010 to present, is the first long-term ground-based study of trace gases in this region. Observations of gas-phase iodine species were made using Long Path Differential Optical Absorption Spectroscopy (LP-DOAS), Multi-axis DOAS (MAX-DOAS) and Resonance and Off-resonance Fluorescence by Lamp Excitation (ROFLEX). These measurements were supported by ancillary measurements of ozone, nitrogen oxides and meteorological variables. Selective halocarbon and ultrafine aerosol concentration measurements were also made. [2]  MAX-DOAS observations of iodine monoxide (IO) display a weak seasonal variation. The maximum differential slant column density was 3.8 × 10 13 molecule cm -2 (detection limit ~7 × 10 12 molecule cm -2 , or ~0.8 pptv). The seasonal variation of reactive iodine IO x (= I + IO) is stronger, peaking at 1.6 pptv during the warm season (February-April). This suggests a dependence of the iodine sources on the annual cycle in sea surface temperature, although perturbations by changes in ocean surface iodide concentration and solar radiation are also possible. An observed negative correlation of IO x with Chlorophyll indicates a predominance of abiotic sources. The low IO mixing ratios measured are not consistent with satellite observations, if IO is confined to the MBL. The IO x loading is consistent with the observed absence of strong ozone depletion and nucleation events, indicating a small impact of iodine chemistry on these climatically relevant factors in the Eastern Pacific MBL.