• Acronym: WG 50
• Parent Committee: POC
• Term: PICES-2021 – PICES-2024
• Co-Chair: Prof. Bo Qiu <bo@soest.hawaii.edu>
  Co-Chair: Dr. Yisen Zhong <yisen.zhong@sjtu.edu.cn>
• Mailing List

To improve the understanding on the ocean physical processes that relate to living marine resources is one of the main goals of POC. To this end, much effort has been made towards the ocean mesoscale dynamics and its impact on the marine ecosystem, while the sub-mesoscale processes, of one or two orders smaller in spatial scale, have received comparatively few attentions. The sub-mesoscale process is a ubiquitous phenomenon over the entire ocean and has been a front edge of oceanography during past decade. The PICES Working Group 38 (WG 38) on Mesoscale and Sub-mesoscale Processes ended this year. While WG 38 has done a detailed and thorough work on the mesoscale processes on the North Pacific, the sub-mesoscale processes were not focused on sufficiently and completely due to the large volume of mesoscale studies. It is therefore timely to transition from mesoscale to sub-mesoscale at this moment on the basis of the results of WG 38.

Sub-mesoscale processes are relevant to ocean primary productivity because they support large vertical velocity with timescale similar to the phytoplankton growth, which will ultimately influence the upper trophic levels and food chain. This new group aims to “improving our essential knowledge on the sub-mesoscale processes by integrating the sub-mesoscale-permitting observation dataset, developing and evaluating the high-resolution coupled model in the North Pacific, particularly in the coastal areas and others with important living resources”. The establishment of this group helps address the FUTURE goal on the variability of marine ecosystem under natural and anthropogenic forcings across scales. The working group will also develop tight collaboration with national and international work groups and promote more studies on this topic.

1. Review the recent progress on the submesoscale observation techniques and model skills in the North Pacific
   Thanks to the advance of computer and instrument technology, the observation and simulation of submesoscale processes have made a huge progress during past decades. The WG will carry on a thorough review on previous submesoscale studies in the North Pacific by regions. Particular interest will be paid on different submesoscale dynamics that dominate in different regional seas and in the open ocean such as the western boundary current (Kuroshio) and its extension, eastern boundary current and associated upwelling, the North Pacific Transition Zone as well as the equatorial areas etc.
   
   
2. Review the current studies on the ocean submesoscales and their role in the marine ecosystem in the North Pacific
   The impacts of submesoscales on the local marine system is one of the main focuses in this work group. Comparing with the Atlantic Ocean, less has been done in the Pacific. In view of this, we will review the role of submesoscale dynamics in regulating the marine ecosystem not only in the Pacific but also over the other world oceans. We will identify which and how the submesoscale processes influence the local primary productivity and other living creatures such as zooplankton, fish and even sea birds.
   
   
3. Identify how and which submesoscale processes interact with local marine ecosystem in the regional areas
   The results of the TOR 1 and 2 will be very instructive to our submesoscale-ecosystem studies in the North Pacific. We will identify the major submesoscale process in the regional areas of the North Pacific using the existing numerical simulations (e.g., MITgcm llc4320) and/or building our own regional high-resolution models. Combined with the observed data like nutrients, chlorophyll and/or coupled biological model, we will be able to determine the role of submesoscale processes in the local ecosystem and clarify the bio-physical interaction across scales.
   
   
4. Evaluate the integrated effects of submesoscale physics on the ocean primary production in the North Pacific
   The integrated effects of submesoscale processes that the WG proposes to evaluate include both the overall long-term variability of primary production and regional ecosystem structure change under the climate forcings during past decades and future projections. This goal also serves as an effort towards the UN decades of Ocean Sciences for sustainable development and the UN SDG 14 (Life below water).
   
   
5. Promote the national research on ocean submesoscales and the international collaboration with worldwide experts
   As mentioned above, the submesoscale studies have received much less attention even in PICES countries. The WG will engage in the activities to promote the national research on ocean submesoscales as well as international collaboration with renowned research groups in this field. By means of this new impetus, we anticipate expanding the influence of our WG and PICES and attracting more scientists to join in. We have summoned an onsite and online submesoscale workshop in June this year.