Predicting the variable ocean carbon sink

Uncovering the world's largest carbon sink-a profile of ocean carbon sinks research

As the world's largest carbon sink, the oceans are essential to achieving the 1.5 °C target. Marine ecosystems play a crucial role in the "sink enhancement" process. A deeper comprehension of research trends, hotspots, and the boundaries of ocean carbon sinks is necessary for a more effective response to climate change. To this end, academic literature in the field of ocean carbon sinks was investigated and analyzed using the core database of the Web of Science. The results show that (1) The ocean carbon sink is a global study. The number of literatures in the field of ocean carbon sinks is growing, and the USA and China are the main leaders, with the USA accounting for 31.19% of the global publications and China accounting for 26.57% of the global publications, and the environmental science discipline is the most popular in this field. (2) Keyword burst detection shows that the keywords "sink, sensitivity, land, dynamics, and seagrass" appear earliest and have high burst intensity, which are the hot spots of research in this field; the keyword clustering shows that the global ocean carbon sinks research mainly focuses on three themes: (i) carbon cycle and climate change; (ii) carbon sinks estimation models and techniques; and (iii) carbon sinks capacity and ocean biological carbon sequestration in different seas. Finally, targeted research recommendations are proposed to further match the ocean carbon sink research.

Quantification of Chaotic Intrinsic Variability of Sea-Air CO2 Fluxes at Interannual Timescales

Chaotic intrinsic variability (CIV) emerges spontaneously from nonlinear ocean dynamics even without any atmospheric variability. Eddy-permitting numerical simulations suggest that CIV is a significant contributor to the interannual to decadal variability of physical properties. Here we show from an ensemble of global ocean eddy-permitting simulations that large-scale interannual CIV propagates from physical properties to sea-air CO2 fluxes in areas of high mesoscale eddy activity (e.g., Southern Ocean and western boundary currents). In these regions and at scales larger than 500 km (~5°), CIV contributes significantly to the interannual variability of sea-air CO2 fluxes. Between 35°S and 45°S (midlatitude Southern Ocean), CIV amounts to 23.76 TgC yr-1 or one half of the atmospherically forced variability. Locally, its contribution to the total interannual variance of sea-air CO2 fluxes exceeds 76%. Outside eddy-active regions its contribution to total interannual variability is below 16%.

Skillful multiyear predictions of ocean acidification in the California Current System

The California Current System (CCS) sustains economically valuable fisheries and is particularly vulnerable to ocean acidification, due to its natural upwelling of carbon-enriched waters that generate corrosive conditions for local ecosystems. Here we use a novel suite of retrospective, initialized ensemble forecasts with an Earth system model (ESM) to predict the evolution of surface pH anomalies in the CCS. We show that the forecast system skillfully predicts observed surface pH variations a year in advance over a naive forecasting method, with the potential for skillful prediction up to five years in advance. Skillful predictions of surface pH are mainly derived from the initialization of dissolved inorganic carbon anomalies that are subsequently transported into the CCS. Our results demonstrate the potential for ESMs to provide skillful predictions of ocean acidification on large scales in the CCS. Initialized ESMs could also provide boundary conditions to improve high-resolution regional forecasting systems.

Threats to marine ecosystems are increasing due to ocean acidification, but trends are spatiotemporally difficult to monitor or predict. Here the authors use an Earth system model to accurately predict surface pH changes in the economically and ecologically important California Current System.

Tracking Improvement in Simulated Marine Biogeochemistry Between CMIP5 and CMIP6

PURPOSE OF REVIEW

The changes or updates in ocean biogeochemistry component have been mapped between CMIP5 and CMIP6 model versions, and an assessment made of how far these have led to improvements in the simulated mean state of marine biogeochemical models within the current generation of Earth system models (ESMs).

RECENT FINDINGS

The representation of marine biogeochemistry has progressed within the current generation of Earth system models. However, it remains difficult to identify which model updates are responsible for a given improvement. In addition, the full potential of marine biogeochemistry in terms of Earth system interactions and climate feedback remains poorly examined in the current generation of Earth system models.

SUMMARY

Increasing availability of ocean biogeochemical data, as well as an improved understanding of the underlying processes, allows advances in the marine biogeochemical components of the current generation of ESMs. The present study scrutinizes the extent to which marine biogeochemistry components of ESMs have progressed between the 5th and the 6th phases of the Coupled Model Intercomparison Project (CMIP).