Predictability of extreme events in a branching diffusion model

We propose a framework for studying predictability of extreme events in complex systems. Major conceptual elements -- hierarchical structure, spatial dynamics, and external driving -- are combined in a classical branching diffusion with immigration. New elements -- observation space and observed events -- are introduced in order to formulate a prediction problem patterned after the geophysical and environmental applications. The problem consists of estimating the likelihood of occurrence of an extreme event given the observations of smaller events while the complete internal dynamics of the system is unknown. We look for premonitory patterns that emerge as an extreme event approaches; those patterns are deviations from the long-term system's averages. We have found a single control parameter that governs multiple spatio-temporal premonitory patterns. For that purpose, we derive i) complete analytic description of time- and space-dependent size distribution of particles generated by a single immigrant; ii) the steady-state moments that correspond to multiple immigrants; and iii) size- and space-based asymptotic for the particle size distribution. Our results suggest a mechanism for universal premonitory patterns and provide a natural framework for their theoretical and empirical study

An Assessment of CO2 Uptake in the Arctic Ocean From 1985 to 2018

As a contribution to the Regional Carbon Cycle Assessment and Processes phase 2 (RECCAP2) project, we present synthesized estimates of Arctic Ocean sea-air CO2 fluxes and their uncertainties from surface ocean pCO2-observation products, ocean biogeochemical hindcast and data assimilation models, and atmospheric inversions. For the period of 1985–2018, the Arctic Ocean was a net sink of CO2 of 116 ± 4 TgC yr−1 in the pCO2 products, 92 ± 30 TgC yr−1 in the models, and 91 ± 21 TgC yr−1 in the atmospheric inversions. The CO2 uptake peaks in late summer and early autumn, and is low in winter when sea ice inhibits sea-air fluxes. The long-term mean CO2 uptake in the Arctic Ocean is primarily caused by steady-state fluxes of natural carbon (70% ± 15%), and enhanced by the atmospheric CO2 increase (19% ± 5%) and climate change (11% ± 18%). The annual mean CO2 uptake increased from 1985 to 2018 at a rate of 31 ± 13 TgC yr−1 dec−1 in the pCO2 products, 10 ± 4 TgC yr−1 dec−1 in the models, and 32 ± 16 TgC yr−1 dec−1 in the atmospheric inversions. Moreover, 77% ± 38% of the trend in the net CO2 uptake over time is caused by climate change, primarily due to rapid sea ice loss in recent years. Furthermore, true uncertainties may be larger than the given ensemble standard deviations due to common structural biases across all individual estimates

Addressing Arctic Challenges Requires a Synoptic Ocean Survey

A coordinated effort involving trailblazing science — and icebreaking ships — from many nations is needed to fill gaps in our understanding of the Arctic Ocean and how it’s changing

Constraining regional and global ocean carbon fluxes 1985 to 2018 in RECCAP2

EGU General Assembly 2023, Vienna, Austria, 24–28 April 2023.-- This work is distributed under the Creative Commons Attribution 4.0 LicenseKeeping global warming in line with the Paris Agreement requires rapid reductions in CO2 emissions. Tracking these reductions demands a thorough bookkeeping of natural and anthropogenic carbon fluxes. The second REgional Carbon Cycle Assessment and Processes (RECCAP2) activity of the Global Carbon Project aims to accurately assess land and ocean CO2 sources and sinks through the efforts of hundreds of scientists around the globe. For the ocean component, regional budgets are developed for the global ocean and five large regions for the period 1980-2018. In addition, four ‘special focus’ themes, namely the biological carbon pump, the seasonal cycle, the coastal ocean and model evaluation are addressed. We use state-of-the-art ocean models and observation-based datasets to provide robust estimates of regional CO2 budgets and constrain their uncertainties. Here, we will provide an overview of RECCAP2 activities, and showcase key results focusing on mean ocean carbon fluxes, and their trends and variabilityN

Constraining regional and global ocean carbon fluxes in RECCAP2

WMO International Greenhouse Gas Monitoring Symposium, 30 Jan - 01 Feb 2023, GenevaN