Gonzâlez-Pola et al. 
ICES-WGOH Assessment on Ocean Climate 
Frontiers In Marine Science | www.frontlersln.org 
2 
March 2019 | Volume 6 | Article 103 
1. INTRODUCTION 
Since its founding in 1902, the International Council for 
the exploration of the Sea (ICES) has aimed to increase the 
scientific knowledge of the marine environment and its living 
resources and to use this knowledge to provide unbiased, non 
political advice to competent authorities 1 . Primarily focused in 
the North Atlantic, ICES consists of a network of marine 
scientists that seek to coordinate on ocean monitoring and 
research, with the aim of providing the best available science to 
decision-makers. 
ICES internal coordination relies on a complex structure that 
builds on the work carried out by up to 150 Expert Groups 
(EGs). EGs gather scientists from different countries to address 
specific topics within the broad spectrum of marine science. 
EG members work throughout the year, typically meeting in 
person once per year to work through a series of assigned tasks. 
No financial support is provided by ICES for EGs, so members 
need to find funds from their home institutions or projects. 
This presents a challenge to members and can compromise 
engagement, especially in periods of scarce resources. However, 
the long-term continuity of most EGs indicates that the funds 
invested in their activities are beneficial. 
ICES established the Working Group on Ocean Hydrography 
(WGOH) within this framework in 1976 (ICES, 1977) to 
further the work done by the Hydrography Committee on 
data management and to coordinate cooperative hydrographic 
research within the framework of the World Meteorological 
Organization (WMO). At that time, 15 years ahead of the 
creation of the Global Ocean Observing System (GOOS), ICES 
represented a major partnership within the ocean community 
and a valuable opportunity for international networking, thereby 
inspiring several physical oceanographers to join the group. 
A review of the WGOH activity up to 2009 is given by 
Holliday et al. (2010) within the framework of the Oceans09 
Conference. Currently, the WGOH is composed of nearly 50 
members from 35 institutions and 18 countries around the North 
Atlantic region. 
The WGOH has been active, meeting on a yearly basis, for 
more than 40 years. During these four decades the way we 
observe ocean hydrography has changed profoundly, evolving 
from primarily traditional vessel-based in-situ sampling to 
progressive incorporation of remote autonomous observation 
technologies. Also, the ocean observing community has grown, 
initiatives promoting international coordination have emerged, 
and comprehensive near-realtime ocean state analyses have 
been established as a public service. Meanwhile, the WGOH 
has continued to evolve while preserving the essence of its 
work aimed at providing ICES with information on ocean 
hydrography as a basis for marine ecosystems research and 
resources evaluation. Next we present our view on the future of 
the WGOH, highlighting its long-standing foundation which is 
rooted in international cooperation. 
1 from www.ices.dk/explore-us/what-we-do/Pages/default.aspx 
2. OCEAN CLIMATE STATUS. THE I ROC 
A central component of WGOH annual meetings since its 
formation has been a session devoted to regional reviews 
of ocean climate. These reviews are based on data from 
existing monitoring programs run by individual countries or 
as international collaborations, sometimes in the framework 
of fisheries management programs. Considered together, the 
detailed regional reviews inform our understanding of North 
Atlantic variability and may be used to develop joint strategies 
for global monitoring. 
Over time it became clear that this joint review of ocean 
status was valuable to other expert groups working on topics 
related to marine environment and ecosystems under the ICES 
umbrella. In 1999, the WGOH published the first review 
of previous year ocean climate conditions as an Annex of 
the WG official Report (Turrel, 1999), naming it Annual 
ICES Ocean Climate Status Summary (IAOCSS). A year later, 
the IAOCSS became a standalone document. In 2004 major 
formatting changes were introduced that helped homogenize the 
presentation (Hughes and Lavin, 2004), and key illustrations 
were included summarizing changes observed across the North 
Atlantic. In 2006 the IAOCSS was renamed ICES Report on Ocean 
Climate (IROC) (Hughes and Holliday, 2006). That report first 
incorporated the ISAS large-scale gridded fields produced by the 
LOPS laboratory and Coriolis operational oceanography center, 
a product which exploits the expansion of Argo autonomous 
profilers array (Gaillard et al., 2016). 
In 2013 the WGOH implemented an interactive web version 
of the IROC 2 in collaboration with the ICES Data Center 
(Figure 1). Now the regional timeseries are updated as soon as 
observations are available during the year and the data can be 
freely downloaded. An archive of IROC reports is available on 
the website and summary highlights for current year conditions 
are posted immediately following the WG annual meeting. A 
recent improvement is the inclusion of newly developed indices, 
such as the Subpolar Gyre Index (Berx and Payne, 2017; Hatun 
and Chafik, 2018), which serves as a proxy for the strength 
and extent of the large scale circulation in the North Atlantic. 
Current efforts are focused on further standardization with 
regards to data processing (i.e., anomaly computation) and report 
layout (presentation of regional circulation maps, timeseries 
display, etc.). 
WGOH analyses are based predominantly on existing 
repeated long-term in-situ hydrographic observations at stations 
and sections around the North Atlantic, the Nordic Seas and 
adjacent shelf seas, including the coastal, shelf and deep ocean. 
The idea behind the IROC is that regional experts perform 
analyses applying their specialized knowledge of a region to 
identify the most relevant available observational timeseries 
that support their assessment of hydrographic change. In this 
sense it is important to highlight that the IROC web is not 
a data repository but a heterogeneous collection of specialized 
timeseries. Most series are derived from CTDs deployed at fixed 
stations or along sections, with data extracted from either a single 
2 https://ocean.ices.dk/iroc/