Recap on biologicaloceanography

CO2changes in the last 50 yr

Carbon Cycle

The Carbonate Systemfrom dissolved CO2 gassources of inorganic carbonTotal dissolved inorganic carbon

Carbonic AcidBicarbonate IonCarbon Dioxide and Carbonate systemCarbonate

CO2O2pHacidbasic(m)

Dissolved Gases in the OceanOxygen profile

Distribution of Carbon species in water

from GLODAP climatology

Higher CO2 levels will generally be detrimental to calcifying organisms and that food web structures and biodiversity will likely change, but it is not clear how this might impact overall productivity and top level predators (e.g. fish).CoccolithophoresForamsCoralscalcitecalcitearagonite

Biogeochemical Controls and Feedbacks on the Ocean Primary ProductionWhat can explain the chlorophyll distribution? 1) Subtropical Gyres2) Upwelling Regions3) Subpolar Gyres4) HNLC regions

Nitrogen appears to be the control during modern time.Where nitrogen can be brought at the surfacethere is higher productivity: Upwelling regionsand subpolar gyresException: HNLC regions, particularly in the Southern ocean The Iron Problem Ocean nutrient inventory

What are the controls on Export Production?

Southern Ocean HNLCMap of annual average nitrate concentrations in the surface waters of the oceans. Data from Levitus, World Ocean Atlas, 1994.

Advanced Very High Resolution Radiometer (AVHRR) images of particle transport in the atmosphere between June and August.

Biophysical interactionsWind-driven gyre circulation for surface distributions;MOC for concentrations at depth

North-south sections of (a) temperature, (b) salinity, and (c) oxygen along the 30oW transect in the Atlantic ocean. Note the salinity tongues indicating the interleaving of water masses from sources in the Antarctic and the North Atlantic.

Pacific

SummaringThe large scale wind-driven circulation explains the (large scale) distribution of chlorophyll. We need to consider the biology to explain the distribution of nitrate (remember the high latitudes and the iron problem!)

The thermohaline circulation explains the vertical distributions of oxygen and NO3 and the differences between the basins at depth

The Nitrogen CycleThe Demand Side.Denitrification.Alternative pathways to N2.The Supply SideNitrogen Fixation: the usual suspects.New diazotrophs and how they work.

Who Cares?Broad reaches of the ocean are N-limited.Recycling of N within the water column supports biological production, butInjection of new N into the upper water column is required to support export production.The N and C cycles are tightly coupled through biological production of organic matter (C:N 7).

The N cycle therefore plays a key role in regulating the C cycle!

NO3ChlorophyllLargedetritusOrganic matterN2NH4NO3Water columnSedimentPhytoplanktonNH4MineralizationUptakeNitrificationNitrificationGrazingMortalityZooplanktonSusp.particlesAerobic mineralizationDenitrificationN2FixationMix Layer depthOceanic N Cycle Schematic

Major Biological Transformations of Nitrogen(Inspired by Codispoti 2001and Liu 1979)

The major oceanic inputs and outputs of combined N are largely separated in space.Denitrification is restricted to sediments and anoxic water masses.N2-fixation is common in oligotrophic surface waters (e.g., the central gyres of the major ocean basins).

N* Distribution Shows Interplay Between N2-Fixation and DenitrificationN* = 0.87( [NO3-] - 16[PO43-] + 2.9) (Gruber & Sarmiento 1997)

What else?Time-dependence: waves, eddies, convection, ocean-atmosphere interactions and various modes of variability from intraseasonal to inderdecadal (ENSO, NAO, PDO, NPGO .)

La NinaconditionsEl Ninoconditions

in the North PacificPacific Decadal Oscillation

Anomaly PDO Negative PhaseMean Sea Level PressureAnomaly PDO Positive Phase

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The NPGO (North Pacific Gyre Oscillations)North Pacific dominant mode of oceanic variability: the PDO and NPGO (left), are driven by the first two dominant modes of atmospheric variability evident in sea level pressure, the Aleutian Low variability and the NPO.Di Lorenzoet al.GRL 2008

Variability of subsurface nitrate (NO3). (A) Mean subsurface (150m) NO3 from ROMS model over 1975-2004. (B) First mode of variability for model subsurface (150m) NO3 anomaly inferred from EOF1. (C) Timeseries of NPGO index (black) compared to PC1 of NO3 (R=0.65, 99%), observed mix layer NO3 at Line-P [Pea and Varela, 2007], and observed NO3 from CalCOFI program (R=0.51, 95%).

The North Atlantic Oscillation IndexThe NAO index shows large variations from year to year. This interannual signal was especially strong during the end of the 19th century.

Sometimes the NAO index stays in one phase for several years in a row. This decadal variability was quite strong in the second half of the 20th century.

more stormsfewer stormsSST Anomalies [C]Positive NAODryWetDryWetStronger CurrentsNegative NAOWeaker Currents

Impacts of the NAOMartin Visbeck

*******Photosyntesis is the main contributor to the development of oxygen in the atmosphere. @.2 billion years ago organic C deposits.***