GEOTRACES: The Importance of Temporal Variability

Peter SedwickBermuda Institute of Ocean Sciences

• meridional variation on dissolved Fe in upper 100 m of water column ~0.5 nM

• GEOTRACES basin-scale ocean sections may extend over time periods of 1-3 months

or more

• observations not synoptic with respect to eolian input and biological uptake/export

(Fe, Al, Co, )

• possibility of seasonal juxtaposition of data from meriodional sections crossing the

equator

Period: 19 May-11 August, 2003

Data: C. Measures and W. Landing,from GEOTRACES Science Plan

(www.geotraces.org)

Sargasso Sea: apparent seasonal change of ~1.5 nM dissolved Fe in response to eolian input

Spring 200429-30 April, 2004

Early Summer 20041-5 June, 2004

Summer 200324 July–6 August, 2003

Seasonal evolution of dissolved Fe in a mode-water eddy (April-July 2007):

• for Fe and other eolian-supplied TEI’s, temporal variability is dominant mode of

surface variation

• biogeochemical models require climatology of TEI’s, not ‘snapshots’ of spatial

distribution

• need to view section data in context of potentially large seasonal/interannual

changes

• how can GEOTRACES assess this temporal variability?

1. anchor sections to time-series observations (BATS, TENATSO, ETSOC, new sites… )

2. perform repeat/intersecting sections during different seasonal periods

AGU-ASLO-TOS 2008 Ocean Sciences Meeting · 2-7 March 2-7 2008 · Orlando, Florida, USA

Abstract deadline: Oct 2

22. Trace Metal Biogeochemistry - Interactions Between Atmosphere and Ocean

Organizers: Philip W. Boyd, Mark L. Wells, Peter N. Sedwick, Benjamin S. Twining

It now is evident that trace metals have entered the biogeochemical mainstream through their pivotal role in

the cycling of carbon, silicon, nitrogen, sulfur and phosphorus. The field of trace metal biogeochemistry is

rapidly evolving, in part through international programs like GEOTRACES, SOLAS and CLIVAR, but a series of

major challenges limit our abilities to incorporate trace metals into models of major element cycling. Trace

metal supply to the upper ocean from both underlying waters and atmospheric aerosol transport is poorly

constrained, as is trace metal incorporation into biological processes and their export to the deep ocean. An

earth system approach is required to fully comprehend the elemental cycles of trace metals, and the

increasing use of stable isotopic tracers likely will be an important stepping stone to meet this challenge.

These and other trace metal studies are needed to underpin modeling efforts aimed at understanding how

ocean biogeochemistry impacts global climate in both the past and into the future. We encourage submissions

from the cellular to the ocean basin scale that address these critical issues