Marine Research & Climate Change [2024.H2]

2024.07 Ocean Temperatures Resume Record Highs
After briefly dipping below 2023 levels, the 2024 global sea surface temperatures are back at record high levels for the time of year. The peak of 20.97°C on 12 July was at 4.56σ above the 1982-2011 mean.

2024.09 Gulf Of Mexico at Record Highs

2024.09 – World’s oceans near critical acidification level (Potsdam Institute, DE)

2024.10

📈 The rate of ocean warming has doubled over the past 20 years. The rate of sea level rise has doubled since the 1970s.
🌊 The ocean is becoming increasingly acidic, and sea ice is rapidly decreasing.
♨️ Marine heatwaves cause biodiversity loss and ecosystem degradation.
📄 Copernicus Marine Ocean State Report (OSR8) by von Schuckmann et al (2024) published 30 Sept 2024.

Projected Changes to Characteristics of El Niño-Southern Oscillation, Indian Ocean Dipole, and Southern Annular Mode Events in the CMIP6 Models – Chung et al (2024)

Abstract
In this study we analyse projections of future changes to the El Niño Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), and Southern Annular Mode (SAM) using the latest generation of climate models. Multiple future scenarios are considered. We quantify the fraction of models that project future increases or decreases in the frequency and amplitude of ENSO, IOD, and SAM events in the late 21st century. Changes to the frequency of co-occurring and consecutive driver phases are also examined. We find that while there is large inter-model spread, the most common pathways correspond to more frequent ENSO events; weaker, less frequent IOD events; and stronger, but less frequent austral spring SAM events.

There is no clear consensus on the change to the frequency of concurrent events, though we find a significant increase in La Niña- and El Niño-only events occurring with neutral IOD and SAM. We also find a significant increase to the frequency of consecutive positive IOD events under a high emissions scenario, but no significant change to the frequency of consecutive ENSO or negative IOD events. In most models, the correlation between drivers, that is, ENSO and IOD, and ENSO and SAM, does not significantly change between the late 20th and late 21st century. These results indicate a high degree of internal variability in the models.

Key Points
– Using all available models and ensemble members, the latest generation of climate models project an overall increase to the frequency of El Niño-Southern Oscillation (ENSO) events but a weakening and decrease in Indian Ocean Dipole (IOD) events in the late 21st century. The Southern Annular Mode (SAM) is also projected to strengthen in austral spring
– There is less consensus among models on projections of frequency change of concurrent (co-occurring) climate driver phases and consecutive ENSO and IOD phases
– Internal variability remains a large source of uncertainty. Multi-model mean results can differ markedly depending on the subset of models used

Plain Language Summary
Year-to-year climate variability impacts ecosystems and billions of people around the world. Major drivers of this variability in the Southern Hemisphere include the El Niño Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), and the Southern Annular Mode (SAM). As anthropogenic activities continue to impact the climate, and further change is inevitable, we need to improve understanding of how these climate drivers will change. Here we use the latest generation of climate models to investigate how the strength and frequency of these three climate drivers are projected to change over the remainder of the 21st century. We investigate changes to these drivers individually, as well as changes to the frequency of these drivers occurring simultaneously or consecutively. While there is still a large amount of inter-model spread, the most common model projections are: more frequent ENSO events; weaker and less frequent IOD events; and stronger, but less frequent SAM events. A statistically significant increase in the frequency of consecutive positive IOD events in the high emissions scenario is also found.

So how might these complex interactions of climate drivers affect the Maldives’ weather in the coming decades?
Based on further Reefscapers research and AI interpretation.

• ENSO: More frequent El Niño events may drive intense rainfall and storms, while La Niña could enhance dry conditions.
• IOD: Milder weather patterns due to weaker IOD; extreme positive IOD might harm mangroves by exacerbating salinity issues.
• SAM: Stronger SAM phases could influence wind patterns and ocean currents, impacting marine ecosystems and local weather.

📅 January-March (Northeast Monsoon):

• Typically a dry season, but increased variability is expected due to stronger ENSO influence.
• El Niño: Likely to reduce rainfall, exacerbating dryness and water scarcity.
• La Niña: May slightly increase rainfall.
• Extreme Weather: Occasional very heavy rainfall; tropical cyclones could start to occur more frequently.

📅 April-May (Inter-monsoon):

• Rainfall Intensification: Warming oceans may boost rainfall due to increased atmospheric moisture.
• Irregular Patterns: ENSO and weaker IOD events could result in alternating heavy rains and dry spells.

📅 June-November (Southwest Monsoon):

• Increased Intensity: Heavier rains and stronger winds may lead to flooding.
• Reduced IOD activity could lead to uneven rainfall distribution and occasional dry spells.
• Higher waves, storm surges, and coastal erosion become more significant during storms.

📅 December (Inter-monsoon):

• Erratic rainfall expected due to overlapping ENSO and SAM influences.
• Delayed Retreat: Prolonged rainfall from a lingering SW Monsoon could increase flood risks and disrupt water resources.