An integrative view of the biological carbon pump

An integrative view of the biological carbon pumpfrom the surface ocean to the deep sediment

Sandra Arndt (s.arndt@bristol.ac.uk)

Sandra Arndt (s.arndt@bristol.ac.uk)

The biological C pump

•Controls importance of global ocean & sediments as C sink (or source)

temporal sequestration of C in deep ocean (very fast response)CH2O burial (fast response)weathering-CaCO3 burial (slow response)

•Controls atmospheric O2

•Controls nutrient and O2 distribution in the ocean

•Controls size of hydrocarbon reservoirs

Sandra Arndt (s.arndt@bristol.ac.uk)

Efficiency of the biological C pump

Euphotic/Epipelagic zone (0-200m)

Fexport=10-20% NPP

10-1 yrs

103 yrsDeposition flux

Sediment (0-103-104m)

Mesopelagic zone (200-1000m)

Bathypelagic zone (1000-4000m)

Abyssopelagic zone (4000-6000m)

0 yrs

108 yrs

0.28-30% Fexport

<1-5% Fexport

<0.3% Fexport

CH2O

Fexport=100% NPP

Burial flux

70% Fexport

50% Fexport

13% Fexport

CaCO3

Export flux

Sandra Arndt (s.arndt@bristol.ac.uk)

Spatial variability

Sandra Arndt (s.arndt@bristol.ac.uk)

Spatial variability- Global scale

Henson et al., 2012 Henson et al., 2012

Henson et al., 2012Seiter et al., 2004

Primary Production (gC m-2 yr-1) Export Efficiency Peff=Fexport/PP

Transfer Efficiency Teff=F2000m/Fexport

Sediment TOC (wt%)

Sandra Arndt (s.arndt@bristol.ac.uk)

Spatial variability- Global scale

Arndt et al., ESR, in press

Regional patterns of organic matter quality in surface sediments

Sandra Arndt (s.arndt@bristol.ac.uk)

Spatial variability- Global scale

Seiter et al., 2005

Hensen et al., 1998

PO4 flux(mmol m-2 yr-1)

NO3 flux(mmol m-2 yr-1)

Sandra Arndt (s.arndt@bristol.ac.uk)

Spatial variability- Continental Margin

Arndt et al., in press

Mollenhauer and Eglinton, 2007

Lateral transport

Sandra Arndt (s.arndt@bristol.ac.uk)

Spatial variability- Lateral Transport

Schmidt et al., 2007

Marine-dominated inner shelf

Terrestrial mud dominated mid-shelfmudbelt

Starved outer shelf and continental slope

Sandra Arndt (s.arndt@bristol.ac.uk)

Spatial Variability- Continental Margin

Zabel and Hensen, 2006 (modified from Jahnke, 1990)

Sediments are the ultimate sediment trap!

Sandra Arndt (s.arndt@bristol.ac.uk)

Continental Margins-Spatial Variability

unpublished data

Sandra Arndt (s.arndt@bristol.ac.uk)

Temporal variability

Sandra Arndt (s.arndt@bristol.ac.uk)

Temporal variability-Seasonal variability

Lutz et al., 2007

Seasonal variability NPP:Low: Equ. low productivity regions

High: high latitudes, monsoonal and temperate high productivity regions

Balance between seasonality of flux and production reverses with latitude

Sandra Arndt (s.arndt@bristol.ac.uk)

Temporal variability-Seasonal variability

Soetaert et al., 1996

Seasonal variability in CH2O input results in a complex benthic response

Sandra Arndt (s.arndt@bristol.ac.uk)

Temporal variability-Lessons from the past

Example: 1. Pliocene-Pleistocene Transition at Bowers Ridge (Beringsea)

Sandra Arndt (s.arndt@bristol.ac.uk)

Temporal variability-Lessons from the past

Wehrmann et al., 2013

Inverse diagenetic modeling of sediment porwater profiles…

…indicates peak in CH2O deposition flux & quality across transition and thus important changes in the functioning of the BCP

Sandra Arndt (s.arndt@bristol.ac.uk)

Temporal variability-Lessons from the past

Example: 2. Cretaceous Oceanic Anoxic Event

Greenhouse climate, anoxic/sulfidic ocean

Sandra Arndt (s.arndt@bristol.ac.uk)

Temporal variability-Lessons from the past

Arndt et al., 2009

Inverse diagenetic modeling of sediment porwater profiles indicates low reactivity (high preservation efficiency) and thus rapid transfer from surface ocean to deep sediment

Sandra Arndt (s.arndt@bristol.ac.uk)

What causes the spatial-temporal variability?

The efficiency of the biological C pump is mainly driven by the production, transport and alteration of POC

Sandra Arndt (s.arndt@bristol.ac.uk)

What causes the spatial-temporal variability?

1. Ballasting

Model that partitions sinking CH2O in two fractions:

1) ballast associated2) unassociated

Sarmiento and Gruber, 2006

Sandra Arndt (s.arndt@bristol.ac.uk)

What causes the spatial-temporal variability?

1. BallastingSpatial variability of CaCO3 carrying coefficients

Wilson et al., 2012

Sandra Arndt (s.arndt@bristol.ac.uk)

What causes the spatial-temporal variability?

2. Ecosystem Structure

Effect on transport Effect on quality

Micklasz and Denny, 2010

Mayor et al., 2012

Sandra Arndt (s.arndt@bristol.ac.uk)

What causes the spatial-temporal variability?

3. Organic matter source and transport

High quality:Young marine material

Low quality:Old marine materialMix pre-aged, terrestrial material

Arndt et al., in press

Sandra Arndt (s.arndt@bristol.ac.uk)

Representation of the pump in Earth System Models

Arndt et al., in press(adapted from lutz et al., 2002)

•Flux:

Simple power-law expression with constant scaling factor (Martin curve, Martin, 1987):

Limit ability of models to predict response of the BCP to environmental perturbations and climate change

•no sediments€

F(z) = Fexp⋅z

z0

⎛

⎝ ⎜

⎞

⎠ ⎟

b

Sandra Arndt (s.arndt@bristol.ac.uk)

Conclusions

Biological carbon pump is a complex set of interlinked processes that act along the surface ocean- deep sediment continuum

Its functioning and efficiency is highly variable in time and space with important implications for global climate and biogeochemical cycles

Existing Earth system models include empirical, highly simplified and decoupled representations of the biological carbon pump that are not related to factors that control the quantity and quality of the flux

Thank you!

Sandra Arndt (s.arndt@bristol.ac.uk)