Comments and inputs for the PRIMO project

Physics in the OMZ of the ESP

Main Research questions

What is the transport of the PCU and what is its spatio-temporal variability?.

What are the main mechanisms transporting oxygen to the OMZ?. Evaluation of advection associated with different flows of the ESPCS, the role of the turbulent diffusivity on the oxygen transport toward the OMZ.

What prevents the southward extend of the ZMO and what is therefore the role of Chile-Peru Current?

The tropic-subtropics connections in the SEP

- Role of the Coastal Trapped Waves on the vertical structure of the OMZ.

- Role of Rossby waves on the offshore extension of the OMZ.

Variability of upwelling in the OMZ

How does the upwelling contribute to the vertical structure of the OMZ?

Mesoscale activities and the OMZ

Document processes associated with mesoscale eddies (eddy transports + lateral diffusion).

Subducted intermediate waters and the OMZ

Document vertical and horizontal mixing processes. - Does the strong salinity vertical gradient (low salinity water near the surface and high salinity at OMZ level) prevent the mixing of low O2 waters? - Which other mechanisms (e.g. thermal stratification) prevent the vertical mixing of surface oxic and low O2 subsurface waters? - What is the contribution of the horizontal mixing to the OMZ spatial heterogeneity?.

National and international context

National programs

Some of the objectives related to PRIMO are associated to the ongoing Research Programs in IMARPE :

A. “Dynamics of Coastal Upwelling, Biogeochemical Cycles and Paleo-oceanography of the Humboldt Current Ecosystem”. This program comprises the following projects:

- “Seasonal and interannual variability of bio-oceanographic parameters in selected areas”,

- “Interactions of the OMZ with organic carbon sedimentation and benthis processes” - “Paleo-oceanographic studies in the continantal margin”.

B. “Effects of ENSO and decadal changes on the regional circulation, water masses and biological communties”

- “Spatial and Temporal Variability of the Surface and Subsurface Circulation off the Peruvian coast in association to ENSO”.

The PRIMO oceanographic cruise

Sampling strategy for the PRIMO oceanographic cruise between 10°S (Peru) and 30°S (Chili),: 195 hydrographic stations and 4 3-day fixed stations in two legs, Callao-Iquique, Iquique-Coquimbo.

The main components of the cruise are :

a series of four 3-day fixed stations in the Humboldt current system (Paita, Chimbote, Pisco, Iquique and Coquimbo). During the whole cruise, continuous records of surface temperature (SST), salinity (SSS), fluorometry, pCO2, pN2O, 0-700m ADCP currents as well as surface classical meteorological parameters will be obtained.

Stations will include CTDO2 casts to the bottom or 1000m, whichever shallowest, and 24 10-liter bottle Rosette samples. Station spacing may vary from 10 nm on sections to 30 or 60nm on transects between sections.

In addition, sediment sampling will be carried out as follows: Paita 1 multicore (instead of Chala)Chimbote: 5 multicores Pisco: 5 multicoresIquique: 5 multicoresAntofagasta : 1 multicore Coquimbo: 5 multicoresConcepcion : 5 multicores

-90° -85° -80° -75° -70°

-90° -85° -80° -75° -70°

Longitud

-30°

-25°

-20°

-15°

-10°

-5°

0°

-30°

-25°

-20°

-15°

-10°

-5°

0°

Latitud

Manta

La Libertad

Talara

Paita

Chicama

Chimbote

Callao

Punta Caballas

San Juan

Ilo

Arica

Iquique

Punta Lobos

Antofagasta

Paposo

Callao-Paita-Chimbote540+200+450mn=5 d15 stat. (1d)Paita fixed stat. (3d)

Sampling strategy for the PRIMO oceanographic cruise between 05°S (Peru) and 30°S (Chile),: 210 hydrographic stations and 4 3-day fixed stations in two legs, Callao-Paita-Iquique, Iquique-Coquimbo.

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Paita, an upwelling centre where local forcing interacts with a recurrent regional forcing (e.g. pulses of advective transport of equatorial surface waters and of moderately oxygenated subsurface waters) is proposed due to its position as northern boundary of the Humboldt Ecosystem, and its long-term hydro-biochemical data base.

2.4.3 Table: Summary of necessary ship-time for the different operations.

Leg 1 Leg 2

1° Callao-Paita-

Chimbote

2° Chimbote-Pisco

3 : Pisco – Atico

4 : Atico – Ilo -

Iquique

5 : Iquique –

Antofagasta

6 :Antofagasta -

Coquimbo

7 : Coquimbo -Concepcion

Stations 15 15 43 38 19 14 66

Route + stations

(5d + 1d)6 d

3.0 days 4,5 days 4,4 days 2.5 days 2.9 days 7.3 days

Fixed stations

3 days 3 days 3 days - 3 days - 3 days

Moorings work

- 1 day 1 day - 1 day 1 day 1 day

Total time 9 days 7.0 days 8.5 days 4.4 days 6.5 days 3.9 days 10.3 days

Calendar D1-D9 D10-D16 D17-D24 D25-D28 D24 to D30 D30 to D34 D34 to D44

Notable operations

D1: Ship loadingRecover ADCP mooring, D2 Fixed St., D4- D6Coring, D3

Fixed St., D10-D12

Atico section,

D17Ilo section, D20 – D21

Coring, D21

(exchange of scientific

crew)

Fixed St., D24-D26Mooring work, D27D22 à D23 : Stop in Iquique

25°S section, D31

Fixed St. D40-D4233°S section, D36D45, ship unloading.

BIOGEOCHEMICAL SECTION (1.2.2.1 Processes involved in sustaining the OMZ)

Concerning the overall structure of this section it is necessary to rewriting, the following structure is suggested:

1.2.2. Biogeochemical processesThe OMZ is sustained by different biogeochemical processes that occurs in the water column and sediments. These processes impact the oxygen concentration of these areas and, in turn, are strongly impacted by the presence of minimum oxygen conditions. They concern the following processes:

1.2.2.1 Production of organic matter1.2.2.2 Remineralization of organic matter and nitrogen

cycling1.2.2.3 Trace metals speciation1.2.2.4 Transfer and export of organic matter1.2.2.5 Benthic biogeochemical processes

• 1.2.2.1. Production of organic matterShould contain the topics related with new and regenerated primary production, community structure, carbon and nitrogen uptake (see PRIMO document).

• 1.2.2.2. Remineralization of organic matter and nitrogen cycling. Should contain the section of biogenic elements mapping (the text was expanded with more background), OM respiration pathways (POM and DOM), Nitrogen processes (ammonium regeneration, nitrification, desnitrification, anammox) and the structure of the related community.

• 1.2.2.3. Trace metals speciation (Fe, Zn, Co, Cd) - see PRIMO document

• 1.2.2.4 Transfer and export of organic matterShould contain, studies with micro/meso zooplankton, grazing activity, sinking particles.

1.2.2.5 (1.2.2.2) Benthic biogeochemical processes

The overall text structure and objectives are ok for us.

Should contain:

a. Transport rates• The text concerning the sedimentation rates was expanded,

indicating the use of gamma and alpha spectrometry, as well as AMS-14C. It is suggested to evaluate the feasibility of using Ra226 as a tool within the time window of the past 1000 years.

b. Redox conditions, respiration pathways and sediment composition• Core and in vitro incubation experiments are proposed to

measure rates of CO2 production, nitrogen trasformation and fluxes, and sulphate reduction in the sediment/water interface.

c. Benthic community structure and function

• The text was expanded with more background information on benthic community features in the HCS.

• For assessing bioturbation we suggest to combine indirect estimates from short-lived radionuclide profiles, vertical profiles of benthic biomass and functional groups, luminophore experiments, and image analyses from X-radiographies of the upper sediment layer.

• Biological information (micro-, meio- and macrofauna) will also contribute to a better understanding of the imprint and interactions of the biological activity with biogeochemical processes and proxies preservation.

Peruvian participants in PRIMO

Physical OceanographyCurrentmeter moorings and data processing : Luis Pizarro, Luis VásquezOnboard CTD/ADCP hydrography and data processing: Luis Vásquez, José TenorioRemote sensing : Mario Ramírez, N.

Domínguez

BiogeochemistryPhytoplankton/flow citometry : Sonia SánchezMesozooplankton/microzooplankton communities, diel migration :Patricia AyónNitrogen cycling in the water column: Michelle GracoPrimary Production*: Georgina Flores, Jesús Ledesma pCO2, TCO2 distribution and Alkalinity: Jesús Ledesma, G. FloresBioturbation (from radionuclide profiles): Dimitri GutierrezSediment comm. respiration rates (from CO2 production): Dimitri Gutiérrez, M. GracoNitrogen cycling in the sediment/water interface: Michelle GracoBenthic community structure: Luis Quipúzcoa

(Macrofauna), Edgardo Enríquez (Meiofauna),

Luis Quipúzcoa, Wilbert Serrano (Microfauna, /DAPI, CTC and FISH?)

Proxy callibrations and Sediments

Sedimentation rates (from radionuclide profiles with Paleotropique and LSCE) :Dimitri Gutiérrez

Bulk CNS, Rockeval and C, N isotopes (with Paleotropique):Dimitri GutiérrezMineralogy (DRX, FTIR with Paleotropique): Federico VelazcoMineralogy (Redox sensitive metals with Paleotropique): Juana SolísDiatoms : Pedro Tapia (UPCH), F.

ChangFish scales : Renato SalvatteciBenthic forams : María Morales

(INGEMMET), Sergio MayorPlankton forams : María Morales

(INGEMMET)

------------------------UPCH: Universidad Peruana Cayetano HerediaINGENMET: Instituto Nacional Geologico y Metalurgico

Modelling

Numerical oceanographical modelling : José Pasapera, Augusto IngunzaNumerical meteorological modelling/MM5 : Yamina Silva (IGP)

Subsurface current fields validation : Carmen Grados, Roberto FloresBiogeochemical modelling validation: Georgina Flores

Biogeochemical dynamical modelling : Jorge Tam, Augusto IngunzaBiogeochemical model parameterization : Michelle Graco

---------------IGP : Instituto Geofisico del Peru