Oceanography | Vol. 37, No. 2
INTRODUCTION TO THE
SPECIAL ISSUE ON
TWENTY YEARS OF GEOTRACES
AN INTERNATIONAL STUDY OF THE MARINE BIOGEOCHEMICAL
CYCLES OF TRACE ELEMENTS AND ISOTOPES
INTRODUCTION
This special issue of Oceanography cele-
brates the transformational findings of
the international GEOTRACES program
in chemical oceanography, 20 years after
drafting of the GEOTRACES Science
Plan in 2004 (GEOTRACES Planning
Group, 2006). With the section cruise
phase of the program ending soon, and a
planned pivot toward smaller- scale pro-
cess studies, this is an opportune time
to look back at the achievements of
GEOTRACES during the last two decades
and to highlight some of the advances in
our understanding of the processes that
determine the oceanic distributions of
trace elements and isotopes (TEIs).
GEOTRACES
GEOTRACES is a cooperative interna-
tional effort comprising scientists from
35 countries, supported by national fund-
ing agencies, and guided by international
steering committees. Since 2008, the pro-
gram has carried out oceanographic,
World Ocean Circulation Experiment
(WOCE)-style “section” cruises through-
out all the ocean basins. Rigorous inter-
calibration efforts stand at the foun-
dation of GEOTRACES to ensure that
basin-scale analyses made by individ-
ual nations can be compared with-
out question. This has been achieved
primarily by occupation of “crossover”
stations between cruises hosted by dif-
ferent countries—perhaps the most
evocative was a meeting of German and
US GEOTRACES Arctic cruises at the
North Pole in 2015. Moreover, the drive
for publicly available synthesized data-
sets has resulted in the production of
an online electronic atlas (https://www.
egeotraces.org/) and the release of three
intermediate data products to date, with
a fourth expected in 2025. These efforts
have led to a sea change in the quantity
of high-quality TEI data available for the
ocean, coupled with many advances in
our understanding of the biogeochemical
processes that determine these distribu-
tions (Anderson et al., 2014).
ARTICLES IN THE
SPECIAL ISSUE
This special issue begins with reflec-
tions from junior and senior scien-
tists on the GEOTRACES program,
the benefit of a multi-tracer approach
for answering biogeochemical ques-
tions, and what life is like aboard a
GEOTRACES section cruise (Anderson,
Halbeisen, and Jeandel). A key suc-
cess of GEOTRACES lies in the rigorous
intercalibration of all data incorporated
into its products, a process overseen
by the Standards and Intercalibration
Committee. This achievement is based
on crucial cooperation among scien-
tists who openly shared protocols, as
discussed in Aguilar-Islas et al., and
allows for both a holistic view of TEI
cycling within a basin (e.g., Arctic
Ocean; Jensen and Colombo) and
synthesized intermediate data prod-
ucts that are valuable for research, edu-
cation, and outreach efforts (as outlined
by Schlitzer and Mieruch-Schnülle).
In addition, from an education and out-
reach perspective, the GEOTRACES
program office has produced a series
of short educational videos, which are
highlighted by Masferrer Dodas et al.
Several articles in this issue focus
on “key parameters,” tracers that are
deemed essential to the GEOTRACES
program. For example, Anderson and
Conway et al. both focus on dissolved
iron and how GEOTRACES has elegantly
demonstrated the utility of a multi-tracer
approach and the unexpected and per-
sistent nature of iron from deep bound-
ary sources such as marine sediments
and hydrothermal venting. Fitzsimmons
and Steffen take a deeper dive into
how GEOTRACES research on hydro-
thermal plumes have transformed our
understanding of which TEIs are sup-
plied or consumed by hydrothermal
systems before influencing the wider
im M. Conway, Jessica N. Fitzsimmons, Rob Middag, Taryn L. Noble, and Hélène Planquette
FROM THE GUEST EDITORS