• PICES Acronym: WG59
• Parent Committees: BIO, POC
  
• Established: June 2026 (GC Decision 2026/S/6)
• Term: IGC-2026 to IGC-2029
• PICES Mailing List

This Working Group focuses on basin-scale connectivity across the North Pacific Ocean, emphasizing linkages among physical and biogeochemical processes. Many physical, biogeochemical, and ecosystem events observed in one region of the North Pacific are driven by processes originating elsewhere in the basin. The central objective of the Working Group is to identify biogeochemical properties for which these connections can be traced from large-scale drivers to regional responses, and to quantify the associated pathways, timescales, and impacts.

The Working Group builds on the PICES 2025 workshop “Basin-scale processes linking western and eastern Pacific dynamics and biogeochemistry,” which highlighted the importance of viewing the North Pacific as a connected system rather than a set of isolated regional domains. The WG will advance integrative analyses that explicitly link processes operating across the western and eastern North Pacific.

One focal topic will be subsurface oxygen, with the goal of evaluating whether the increasing occurrence of hypoxia events in the eastern North Pacific is linked to changes in ventilation and water-mass formation in the northwest Pacific. A second focus will be oceanic Rossby waves, which originate in the eastern Pacific and propagate westward, with the potential to alter upper-ocean structure and primary productivity in the western Pacific. Additional cross-basin physical and biogeochemical processes will be identified and investigated as the WG progresses.

The North Pacific Ocean is undergoing rapid physical and biogeochemical change, with potentially significant consequences for marine ecosystems. Processes spanning the full basin and crossing national boundaries are difficult to observe and predict, yet essential for understanding emerging ecosystem responses. Key outputs of this Working Group will include improved understanding of basin-scale connectivity, assessment of its relevance for seasonal to longer-term biogeochemical forecasting, and development of a network of PICES scientists trained to recognize regional events linked to remote basin-scale drivers.

1. Identify physical and biogeochemical processes where a driver on one side of the North Pacific leads to a response on the other side. This can include changes in the Arctic regions that provide connectivity across the North Pacific Ocean.
2. For selected processes, describe the pathways, timescales, and impacts of basin-scale connectivity. An initial focus will be on processes driving subsurface oxygen transport in the subpolar gyre.
3. Document how improved understanding of basin-scale processes can be used to interpret and assess the reliability of seasonal and longer forecasts.
4. Identify cases where model based forecasts of biogeochemical variables on annual and longer time scales would support actionable ecosystem risk assessment, early warning, and management advice.
5. Prepare manuscripts for publication describing results from this work.
6. Submit a final report to PICES.

The new PICES Strategic Plan will emphasize ‘actionable science.’ This WG will address ‘actionable science’ by facilitating advances in ocean prediction, particularly for processes having strong ecosystem impacts. Forecasts of biogeochemical variables on seasonal and longer time scales are maturing and becoming operational. Consider the scenario of a forecast that subsurface oxygen will be lower than normal off the west coast of North America and local or regional drivers are not anomalous. Is the forecast trustworthy? The work here will provide estimates of magnitude and time-scales expected if the decline is due to reduced ventilation in the NW Pacific. This can be used to provide an estimate of confidence in the forecast.

By quantifying the variability and the time-scales for the lag between driver and response, there will be a basis for assessing the reliability of forecasts in cases where the response is not driven by local or regional causes.
[Current PICES Strategic Plan]

POC: this WG will build on the work of Manu Di Lorenzo (former POC chair) and others who investigated the North Pacific Ocean’s overall system response to large-scale forcing (e.g. ENSO). The WG will look at different forcing mechanisms but with a renewed focus on connections across the North Pacific.
FIS and BIO: the WG will improve understanding of the drivers of biogeochemical change (e.g. deoxygenation) which impact the distribution of key fish species and sustainability of harvest strategies.
WG-49 (climate extreme events): this work will help clarify the role of climate change in episodic hypoxia in the eastern Pacific
WG-40 addressed climate and ecosystem predictability. At the time of their work forecasting at sub-seasonal to decadal timescales was largely focussed on physical variables; biogeochemical forecasting was still in the early stages of development. This WG will revisit and update their recommendations.
S-CCME: this work will clarify mechanisms by which climate change affects marine ecosystems in the North Pacific.
S-CC: WG will work closely with S-CC members to assess local and basin scale drivers of ocean acidification and deoxygenation.
S-MBM: some bird and mammal species show basin-scale covariance, e.g., in the western and eastern Pacific. MBM can benefit from research into underlying mechanisms of connectivity

CLIVAR – The CLIVAR Pacific Region Panel has developed a working group on “Tropical Pacific BGC-Physical interactions”, aimed at elucidating the impact of physical climate variations on biogeochemical quantities, especially oxygen. The activities of the CLIVAR Panel, although focused in the tropics, can help understand the physical processes most impactful for oxygen levels and distribution. In addition, CLIVAR expertise in many aspects of climate variability and change in the North Pacific can provide a foundational physical understanding of the underlying processes.

A tentative timeline for deliverables is outlined below.

Year 1 (Spring 2027)

• Identify processes that provide physical and biogeochemical connectivity across the North Pacific. Potential topics include a) quantifying the link between ventilation in the NW Pacific and subsurface oxygen in the NE Pacific (Canadian and US continental shelves); b) whether heaving pycnoclines caused by westward propagating oceanic Rossby waves in the North Pacific play a significant role in variability of primary productivity, and c) if changes in micro- and macro-nutrient inputs play an important role in the oxygen budget through changes in export of biogenic material from the surface to intermediate layers (ToR 1).
• Draft literature review of the oxygen inputs to the subpolar North Pacific (location, magnitude, variability), produce a draft oxygen budget for the intermediate waters of the North Pacific subpolar gyre, and develop an analysis of changes in key parameters of the surface density field in the subpolar gyre such as winter mixed layer depth and surface density with a focus on their potential to affect subsurface oxygen (ToR 2).
• Develop plan for model-based analyses of the ventilation, transport, export, and consumption of oxygen in the intermediate layers of the subpolar gyre (ToR 2).
• Develop plans and identify deliverables for other physical and biogeochemical processes (ToR 2).
• Identify members of other PICES Expert Groups interested in identifying pathways to incorporate findings of the WG into forecast models for the biogeochemical state of the North Pacific (ToR 4).

Year 2 (Spring 2028)

• Modelling study on the impact of oceanic Rossby waves on primary productivity in the North Pacific. Do Rossby waves affect productivity in the western North Pacific, and do they inject iron into the euphotic zone in the central North Pacific? (ToR 2).
• Quantify estimate of the time scale for oxygen transport from the northwest Pacific ventilation areas to the west coast of North America (ToR 2).
• Refine deliverables for other processes defined in Year 1 (ToR 2).
• Assessment of the importance of these processes for seasonal and longer time scale forecasting of the biogeochemical state of the North Pacific Ocean (ToR 3).
• Identify and task manuscripts that will be written by WG members (ToR 5).
• Determine (based on results completed) whether a virtual special issue should be pursued (ToR 5).

Year 3 (Spring 2029)

• Document (either via internal reports or journal peer-reviewed manuscripts) the identified key processes across the North Pacific from drivers to responses (events) and provide estimates of the magnitude of the variability and the timescale from driver to response (ToR 2).
• Document (and provide metrics if possible) how improved understanding of basin-scale processes can be used to interpret and assess the reliability of seasonal and longer forecasts (ToR 3).
• Identify pathways to advance the incorporation of identified cross-basin physical and biogeochemical linkages into seasonal to multi-year prediction systems, with the objective of improving the skill, reliability, and interpretability of forecasts of the North Pacific biogeochemical state (ToR 3 and 4).
• In collaboration with other PICES Expert Group members, identify potential use cases where enhanced forecasting on time scales longer than seasonal could usefully inform marine management applications (ToR 4).
• List of manuscripts submitted and those in preparation stage (ToR 5)
• Complete and submit a final report to PICES (ToR 6).