Description: Purpose of Review Subtropical highs are an important component of the climate system with clear implications on the local climate regimes of the subtropical regions. In a climate change perspective, understanding and predicting subtropical highs and related climate is crucial to local societies for climate mitigation and adaptation strategies. We review the current understanding of the subtropical highs in the framework of climate change. Recent Findings Projected changes of subtropical highs are not uniform. Intensification, weakening, and shifts may largely differ in the two hemispheres but may also change across different ocean basins. For some regions, large inter-model spread representation of subtropical highs and related dynamics is largely responsible for the uncertainties in the projections. The understanding and evaluation of the projected changes may also depend on the metrics considered and may require investigations separating thermodynamical and dynamical processes. Summary The dynamics of subtropical highs has a well-established theoretical background but the understanding of its variability and change is still affected by large uncertainties. Climate model systematic errors, low-frequency chaotic variability, coupled ocean-atmosphere processes, and sensitivity to climate forcing are all sources of uncertainty that reduce the confidence in atmospheric circulation aspects of climate change, including the subtropical highs. Compensating signals, coming from a tug-of-war between components associated with direct carbon dioxide radiative forcing and indirect sea surface temperature warming, impose limits that must be considered.

Description: Published

Description: 371–382

Description: 4A. Oceanografia e clima

Description: N/A or not JCR

Description: Decadal climate predictability in the South Atlantic is explored by performing reforecast experiments using a coupled general circulation model with two initialization schemes; one is assimilated with observed sea surface temperature (SST) only, and the other is additionally assimilated with observed subsurface ocean temperature and salinity. The South Atlantic is known to undergo decadal variability exhibiting a meridional dipole of SST anomalies through variations in the subtropical high and ocean heat transport. Decadal reforecast experiments in which only the model SST is initialized with the observation do not predict well the observed decadal SST variability in the South Atlantic, while the other experiments in which the model SST and subsurface ocean are initialized with the observation skillfully predict the observed decadal SST variability, particularly in the Southeast Atlantic. In-depth analysis of upper-ocean heat content reveals that a significant improvement of zonal heat transport in the Southeast Atlantic leads to skillful prediction of decadal SST variability there. These results demonstrate potential roles of subsurface ocean assimilation in the skillful prediction of decadal climate variability over the South Atlantic.

Description: Published

Description: id 8523

Description: 4A. Oceanografia e clima

Description: JCR Journal

Description: Antarctic sea ice prediction has garnered increasing attention in recent years, particularly in the context of the recent record lows of February 2022 and 2023. As Antarctica becomes a climate change hotspot, as polar tourism booms, and as scientific expeditions continue to explore this remote continent, the capacity to anticipate sea ice conditions weeks to months in advance is in increasing demand. Spurred by recent studies that uncovered physical mechanisms of Antarctic sea ice predictability and by the intriguing large variations of the observed sea ice extent in recent years, the Sea Ice Prediction Network South (SIPN South) project was initiated in 2017, building upon the Arctic Sea Ice Prediction Network. The SIPN South project annually coordinates spring-to-summer predictions of Antarctic sea ice conditions, to allow robust evaluation and intercomparison, and to guide future development in polar prediction systems. In this paper, we present and discuss the initial SIPN South results collected over six summer seasons (December-February 2017-2018 to 2022-2023). We use data from 22 unique contributors spanning five continents that have together delivered more than 3000 individual forecasts of sea ice area and concentration. The SIPN South median forecast of the circumpolar sea ice area captures the sign of the recent negative anomalies, and the verifying observations are systematically included in the 10-90% range of the forecast distribution. These statements also hold at the regional level except in the Ross Sea where the systematic biases and the ensemble spread are the largest. A notable finding is that the group forecast, constructed by aggregating the data provided by each contributor, outperforms most of the individual forecasts, both at the circumpolar and regional levels. This indicates the value of combining predictions to average out model-specific errors. Finally, we find that dynamical model predictions (i.e., based on process-based general circulation models) generally perform worse than statistical model predictions (i.e., data-driven empirical models including machine learning) in representing the regional variability of sea ice concentration in summer. SIPN South is a collaborative community project that is hosted on a shared public repository. The forecast and verification data used in SIPN South are publicly available in near-real time for further use by the polar research community, and eventually, policymakers.

Description: Intersessional Science Board Meeting 2023 - Note from the new SB Chair. Future SSC's 9th Intersessional Meeting ~Highlights. PICES 2023 ~ See you in Seattle. The 5th International Conference on the Effects of Climate Change on the World's Ocean ECCWO5 (Together we will work; W1 Workshop Report; W2 Workshop Report; S2 Session Report; S3 Session Report; S10 Session Report; S18 Session Report; S19 Session Report; ECOP Update; Presentation Awards; EuroFish). PICES-MAFF Ciguartera Project - Summary of Activities. Exploring National ECOP hubs in PICES member countries. The 44th Pacific Ecology and Evolution Conference (PEEC). Regional Reports (The Bering Sea: Current Status and Recent Trends; Western North Pacific - Current Status and Updates: Sea surface temperatures for the 2022/2023 cold season; The Northeast Pacific: Update on marine heatwave status and trends). The Continuous Plankton Recorder as a platform for sensor development. ICES Annual Science Conference, 2022: Theme Session J. The Development of the SUPREME Network. Remembering Vera Alexander. PICES by the Numbers: #ECCWO5 Calculated Carbon Emissions. PICES Events Calendar. Your PICES Science Images. Open call for PICES Press submissions|About PICES Press

Description: Published

Description: Non Refereed