Upwelling systems, both coastal and equatorial, are natural laboratories for studying the impacts of multiple stressors on air sea-exchange processes and marine ecosystem services. These systems are characterised by high productivity closely related to the presence of an extensive oxygen minimum zone (OMZ) and low pH-high carbon dioxide values. Active research during recent decades has determined the role of upwelling systems in the exchange of climatic active gases (such as CO2, N2O, and CH4), OMZ variability, and the biogeochemical cycles of nitrogen, carbon, and sulphur.
Current national and international programs investigating upwelling include “Role of Eddies in the Carbon Pump of Eastern Boundary Upwelling Systems” (REEBUS) and SCOR WG 155 on Eastern boundary upwelling systems (EBUS): diversity, coupled dynamics and sensitivity to climate change.
Eastern boundary upwelling systems (EBUS) Conference, Lima, Peru, Sept 2021
Polar Oceans and Sea Ice
Changing sea-ice coverage in the polar oceans is impacting air-sea exchanges of chemically, biologically, and climatically active substances. The dynamics and consequences of changes in sea-ice characteristics and distribution in the polar oceans are critical to understanding and modelling feedback mechanisms and future scenarios of climate change. Sea ice was long assumed to inhibit air-sea gas and material exchange, but extensive research over the last couple of decades has shown that sea ice is a very rich and complex system that actively exchanges with both the atmosphere and the underlying water, and impacts exchanges in surrounding waters. Sea-ice harbors a highly productive ecosystem, which interacts with both the ocean and the atmosphere and supports multiple ecosystem services. Understanding changes to the system is crucial in understanding potential impacts on these ecosystem services. The snowpack on sea ice is a highly reactive environment controlling uptake and release of many photochemically active trace gases, particles and their precursors, interacting with the lower atmosphere and the sea ice underneath. Understanding emission and deposition fluxes above snow on sea ice is critical to assess the impact of a changing sea-ice environment on atmospheric composition (oxidizing capacity, budgets of mercury, halogens and organics), aerosol direct and indirect effects, and climate.
Continue efforts to understand how the structure of sea ice impacts the uptake and release of climatically-active substances to/from the atmosphere and the underlying water. This involves exploring the changing nature of ice, which is generally becoming thinner and warmer, and in the Arctic, increasing pack ice mobility and rafting is potentially redistributing sympagic biological communities throughout the ice. Melt ponds, which are becoming increasingly prevalent in spring in the Arctic, may also represent a significant albeit poorly quantified source of gases and particles to the atmosphere. Thinner ice and enhanced snowfall might cause flooding and snow-ice formation, impacting both ice biology and chemistry. Both processes are more commonly observed in the Southern Ocean. With a more brittle ice pack, more open water is present in the winter, with more potential for direct air-sea gas exchange and changes in pelagic versus sympagic primary production, as well as more seasonal ice formation. Deeper snowpacks may dampen ice-air trace gas fluxes, whereas increased flooding and saltier first year ice may increase salt loading of the snow column with unknown impact on photochemical processes and air-snow fluxes of trace gases, particles, and their precursors. The question of whether air-sea gas exchange rates are enhanced in the presence of a broken, mobile ice cover (including leads and polynyas) is still open, and contradictory results from laboratory and field measurements need to be resolved. The extent to which sea-ice brines directly contribute to deep-ocean carbon sequestration is also still unresolved. Answering these questions requires both detailed process studies (lab, field, and numerical) and integrated, large-scale observation systems.
An effort will be made to coordinate results from the large number of Southern Ocean field campaigns being conducted in 2019 – 2021 by holding a workshop in the Southern Hemisphere in 2021/22.
A research community co-sponsored by SOLAS and CliC, BEPSII focuses on how the biogeochemistry of sea ice influences both the ocean and the atmosphere. Within sea ice, biotic and abiotic processes interact in changing ways throughout the freeze-melt cycle, and thus, sea ice is an active participant in the biogeochemical cycles of many elements, producing climatically active atmospheric aerosols, modulating the surface ocean ecosystem, contributing to substantial seasonal gas fluxes, and possibly facilitating long-term export and carbon dioxide sequestration in deep waters. Near-future priorities for BEPSII include:
- A position analysis (PA) on Antarctic sea ice biogeochemical responses to climate change (An Arctic PA has been submitted to Nature Climate Change)
- A community paper on sea-ice ecosystem services
- A commentary on geoengineering proposals for Arctic sea-ice restoration
- 1-D model intercomparison.
- A sea-ice field school for early-career scientists
- Expert contribution to the sea-ice biogeochemistry, ecosystem, and modelling components of the MOSAiC project
- A coordinated 2nd Ice Algae Model intercomparison Project (IAMIP2)
BEPSII will hold their 2020 meeting virtually and their 2021 meeting in Ventura, USA, alongside the Gordon Conference on Polar Marine Science.
Cosponsored by SOLAS and IGAC, the CATCH mission is to facilitate atmospheric chemistry research within the international community, with a focus on natural processes specific to cold regions of the Earth. Cold regions include areas that are seasonally or permanently covered by snow and ice, from the high mountains to the polar ice sheets and sea ice zones, as well as regions where ice clouds are found. Upcoming activities and priorities for CATCH include:
- Planning of a CATCH focused Gordon Conference
- Develop a joint SCOR working group and research expedition with BEPSII to investigate feedbacks between atmospheric chemistry and sea-ice biogeochemistry
Current national and international programs investigating air-sea exchange in the polar oceans include “Processes Influencing Carbon Cycling: Observations of the Lower limb of the Antarctic Overturning” (PICCOLO), “Shipping Emissions in the Arctic and North Atlantic Atmosphere” (SEANA), and SCOR WG 152 on Measuring Essential Climate Variables in Sea Ice (ECV-Ice).
There have been significant advances in recent years in our ability to describe and mod-el the Earth system, but our understanding of oceanic and atmospheric processes in the Indian Ocean region is still rudimentary in many respects. This is largely because the Indian Ocean remains under-sampled in both space and time, especially compared to the Atlantic and Pacific Oceans. The situation is compounded by the Indian Ocean being a dynamically complex and highly variable system under monsoonal influence. Many uncertainties remain in terms of how oceanic and atmospheric processes affect climate, extreme events, marine biogeochemical cycles, atmospheric chemistry, meteorology, ecosystems, and human populations in and around the Indian Ocean. There are also growing concerns about food security in the context of global warming and of anthropogenic impacts on coastal environments and fisheries sustainability. One impact of global warming is sea level rise, which leads to coastal erosion, loss of mangroves, and loss of biodiversity. Anthropogenic impacts include pollution, with water quality deterioration because of nutrient and contaminant inputs and detrimental ecosystem effects, such as eutrophication and deoxygenation. There is a pressing need for ecosystem preservation in the Indian Ocean for both tourism and fisheries.
The Indian Ocean represents one of the last great frontiers and challenges of oceanographic/atmospheric research. The biogeochemical cycles and ecosystems of the Indian Ocean appear to be particularly vulnerable to anthropogenic impacts (including climate change, eutrophication, atmospheric pollution and aerosol load).
Major research questions to be addressed with high priority are:
- Which processes determine the natural variability of the biogeochemical cycles, ecosystems and atmospheric chemistry over the Indian Ocean?
- What is the effect of the (long-range) transport of air pollution on ocean biogeochemistry, ecosystems, atmospheric chemistry and climate?
- How are human-induced stressors impacting the biogeochemistry and ecosystems of the Indian Ocean?
- How, in turn, are these impacts affecting human populations?