Marine Research & Climate Change 2024-h1

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Our unique link database consists of hand-curated global news & research into marine biology and climate change, with an emphasis on the warming oceans and coral conservation. Updated daily & weekly, and divided into monthly sections to stay updated on breaking news and research articles published worldwide.

If you missed it, start with our🔥 Climate Change guide 🪸 detailing the best international resources for you to make sense of the science of global warming and coral bleaching.

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NOAA infographics coral bleaching

January 2024

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Stony coral tissue loss disease

Stony coral tissue loss disease – Papke et al (2024)

February 2024

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Coral Bleaching in the Chagos Islands

Located in the Indian Ocean, 500km to the south of the Maldives, the Chagos Archipelago comprises 7 geographic atolls and 60+ islands. In previous years, the Chagos reefs have been damaged by coral bleaching events, caused by increasingly elevated global ocean temperatures.

Looking at the ‘Country Comparisons’ image below, we can see the SSTs for Chagos tend to warm one month sooner than in the Maldives, as expected given the relative locations and the warmer currents that head northwards. For the mass coral bleaching events:

  • 1998 – Similar severity, with Chagos at alert level #1 (April-May), and Maldives at level #1-2 (May-June). The recorded SSTs and DHW are similar for both.
  • 2016 – Chagos experienced higher temperatures (and in 2015 too). Alert level #1-2 peaked from mid-March to mid-June, with DHW reaching 18 weeks, causing major coral bleaching and mortality. The Maldives peaked briefly at level #1-2 from mid-April to mid-May, totalling 11 DHW that we know was very damaging for Maldivian reefs.
  • 2024 – Chagos hit level #1 mid-March, and temperatures continue to rise as at 02 April (7 DHW). Therefore, we might expect the Maldives to reach level #1 by mid-April, 1 month later. This year, the Indian Ocean temperatures will likely be further boosted by both El Nino and the positive IOD.

Shepherd et al (2017) describes ‘Coral Bleaching and Mortality in the Chagos Archipelago’ from the global mass bleaching event of 2016. Coral cover was being measured for 20+ years, and after the 2016 bleaching, mortality was very severe and coral cover declined from the ~30-50% range, down to just 5-10%. (Most atolls are uninhabited, so any changes are driven by climate change rather than by local anthropogenic effects).
Local water temperatures increased by 0.3C (ocean reefs) to 0.5C (lagoons) in just 10 years. Numbers of juvenile corals severely declined, suggesting that future recurrences of mass mortalities will occur too frequently for reef recovery as soon as 2029.

Carlton et al (2021) wrote the Chagos Archipelago Final Report as part of a Global Reef Expedition [PDF], from their 2 month assessment of Chagos reefs in 2015 (completed just as the reefs started to bleach). In an interesting follow-up article in 2021, team-member Prof Sam Purkis describes ‘Watching a coral reef die as climate change devastates one of the most pristine tropical island areas on Earth. It wasn’t just small pieces of the reef that were bleaching – it was happening across hundreds of square miles. We were witnessing the death of a reef’.
‘The Chagos reefs could potentially recover – if they are spared from more heat waves. Even a 10% recovery would make the reefs stronger for when the next bleaching occurs. But recovery of a reef is measured in decades, not years. So far, research missions that have returned to the Chagos reefs have found only meager recovery, if any at all.’

Diaz et al (2023) describes ‘Mesophotic coral bleaching associated with changes in thermocline depth’ during field work conducted in 2019-2020. They found coral bleaching at depths of 90m, despite the absence of shallow-water bleaching. The 90m bleaching was associated with sustained thermocline deepening driven by the Indian Ocean Dipole (described above).
As global temperatures continue to rise, shallow coral reef bleaching has become more intense and widespread. Mesophotic coral ecosystems reside in cooler, deeper water (30–150m) and were thought to offer a refuge to shallow-water reefs. But studies now show that deeper ecosystems host diverse endemic communities with limited connectivity to shallow corals.

Chagos: start of coral bleaching (Feb 2024) seen at 60-90m depth, thanks to @Clara_Diaz_974 >

2024.02 Sea Surface temperatures start 2024 with record highs (FT SST by decade)

FT: Global SST reached a record January high of 20.97°C (second-hottest month ever, after August 2023 at 20.98°C).
SSTs have already reached “new absolute records”, with 21.12°C on 4 February 2024.

NOAA CoralReefWatch animation 60pc (25Feb-07Jul) 2024

NOAA Coral Reef Watch: 4-Month Coral Bleaching Outlook
Forecast animation (22-Feb), for the period: 25-Feb to 07-Jul 2024

March 2024

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Interactive Maps:
NOAARECIFALLENMyOcean
PulseOcean Currents Sea Levels

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How could the Indian Ocean Dipole (IOD) affect Maldivian corals in 2024 ?

The Indian Ocean Dipole (IOD) (“Indian Niño”) is an irregular oscillation of SSTs in which the western Indian Ocean becomes alternately warmer (positive phase) and then colder (negative phase) than the eastern part of the ocean. The IOD was first identified by climate researchers in 1999, with coral records (2008) dating back to 1846. There is an average of 4 positive-negative IOD oscillations each 30-years, with each event lasting 6 months. Recent decades show increasing irregularity due to climate change. In addition, an IOD-ENSO interaction contributes to the generation of Super El Niños.

Current forecasts from Australia’s BOM are predicting a positive phase for the Indian Ocean Dipole in 2024. This will likely raise the ocean temperatures around the Maldives, in addition to the El Niño warming event. The IOD might also bring increased rainfall with the arrival of the SW monsoon (late April-May), but this anticipated cooling effect may be too late to significantly help the corals, as initial bleaching effects are already being reported on some Maldivian reefs (photos, below).

IOD timeline positive negative
Maldives 18 March 2024 – Start of coral bleaching (South Huvadhu Atoll)
Thanks to @nixams8
SST DHW GBR & MV bleach years [20Mar24]

Reefscapers infographic using NOAA forecast tools [click to enlarge]
SST & DHW in Australia (GBR) & Maldives, bleachings 1998 & 2016.
As GBR bleaches in Feb-Mar, before MV (Apr-May), we can use the severity of GBR bleaching to try to predict effects in MV in 2024.

NOAA Maldives_prod_quad_composite [2024-03-17]

NOAA: 5km Regional Bleaching Heat Stress Maps and Gauges
In the upcoming weeks, the Maldives is forecast to experence high ocean temperatures (CoralWatch Alert Level #2).

gbr_central DHW (1-13 Mar 24)

Update: Great Barrier Reef (Central) starts to cool.
SST falls below bleaching threshold, and record DHW starts to plateau
(from 1 to 11 March 2024).
Reefscapers animation using NOAA’s GBR Time Series Graphs

SST colour chart (1982 to 25Mar24) [EliotJacobson]

Global SST Anomaly (1982 to Mar 2024) [@EliotJacobson]

Seychelles Bleaching (March 2024)
A good example of the vulnerability of fast-growing Acropora corals to repeated marine heatwave events.
Thanks to Charlotte Dale

Brazil’s marine protected area (MPA Costa dos Corais) Coral Bleaching March-April 2024
Thanks to @pedrohcp – and – Reuters

GBR Extensive Coral Bleaching across the entire reef, North to South (March 2024)
Thanks to: @ProfTerryHughes, @JezRoff, @DrCarlyRandall, Amy ‘intheocean’ Lawson, @johnwturnbull (& flickr),
plus ABC, The Guardian, and The Undertow.

GBR Healthy reef (2023) now bleached (Mar 2024): Before & After (slider) – striking aerial photos taken at the same location
Thanks to Prof Michael Sweet FRSB, @coralseafound, @JezRoff

2023 HEALTHY 2024 BLEACHED

April 2024

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Interactive Maps:
NOAARECIFALLENMyOcean
PulseOcean Currents Sea Levels

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C3S SST 1998 2016 2023-24 (01Apr24)

SST 1998 2016 2023-24 [C3S]

C3S SST Anomaly 1998 2016 2023-24 (01Apr24)

SST Anomaly 1998 2016 2023-24 [C3S]

GBR Mass coral bleaching event update (9 April 2024): Preliminary analysis by CoralWatch team’s @JezRoff
– Satellite data for degree heating weeks (DHW) clearly outline the record intensity and impact.
– 46% of reefs experienced record high DHW.
– New record of 17.7 DHW from southern GBR.
– 37% of GBR has been exposed to three or more >6DHW events in the past decade.
– Mass bleaching events are increasing in frequency and intensity since 1986.
– 31% of the southern “refugia” reefs have been exposed to >4DHW for the first time in over three decades.
– High (4-8 DHW) and severe (8-12 DHW) exposure categories are becoming commonplace.
– The intensification from the first event (1998) through to 2024 is striking.
– Sustained high DHW across much of the reef => predicted high mortality.
– Despite temperatures dropping, many reefs (eg: Heron Island) continue to experience sustained record DHW exposure.
– Awaiting results of in-water surveys
AIMS PDF (15 Apr): Aerial surveys of the 2024 mass coral bleaching event on the Great Barrier Reef

PDF (15 April 2024) – AIMS Aerial surveys of the 2024 mass coral bleaching event on the Great Barrier Reef

  • AIMS Reef Health Updates > 26 April 2024
  • Ocean temperatures started building in late December through to late February throughout all three regions of the Great Barrier Reef, causing the highest levels of thermal stress on record.
  • In March 2024, the fifth mass bleaching event on the Great Barrier Reef was confirmed.
  • This year for the first time, extreme bleaching (90% bleached coral cover) was observed in all three regions of the GBR.
  • 73% of GBR reefs have prevalent bleaching (>10% bleached coral cover).
  • 60% of GBR reefs were exposed to dangerous levels of heat stress (bleaching and mortality risk).
  • 46% of GBR reefs experienced record levels of heat stress.
  • 39% of GBR reefs experienced ‘very high’ to ‘extreme’ (61-90%+ coral cover) levels of bleaching
  • GBR’s southern inshore reefs experienced the most intense and prolonged heat stress ever recorded: SST at +2.5°C above average, and 15 degree heating weeks.
  • By 26 April, the SSTs across the whole Marine Park had cooled to below the average summer maximum (and below the coral stress threshold) but remain above the long-term April average (by +1°C to +1.5°C).

Maldives April 2024 – Coral bleaching (South Male’ Atoll)
Night-time ocean temperatures at 10m depth (usually ~28°C) are hitting a staggering 30°C! 🔥 Thanks to 📷  @nixams8
Also: Twitter video showing bleaching at Kottey Bay, Hithadhoo, Addu City [@KhalylKhaleel]

SST anomalies Copernicus (April 2024) [map_era5_monthlly_sst_percentiles_202404]

Copernicus: Global Sea Surface Temperature (SST) Anomalies (April 2024)
April 2024 SST (global 60°S–60°N) was 21.04°C, the highest on record for the month, and the 13th consecutive monthly record high.
SSTs broke records across many of the world’s oceans (highlighted as ‘warmest’ colour).

May 2024

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Interactive Maps:
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PulseOcean Currents Sea Levels

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GBR flickr John Turnbull [@johnwturnbull]
GBR flickr John Turnbull [@johnwturnbull] April
NIOsst Indian Ocean SST (2024.05.25) [@DrKimWood]

Towards the end of May, SST falls below 2016 levels

Maldives (& Region)

Maldives (& Region): NOAA data tools (as at 25 May 2024)

The current data suggests that ocean temperatures have fallen in the Maldives (and the wider Indian Ocean region).

  • SSTs for the Maldives have fallen below the bleaching threshold, and currently hover around the max monthly mean for May (~30°C).
  • This year’s heat stress does not appear to be as severe as experienced in 2016 (early forecasts were inconclusive).
  • We have observed widespread coral bleaching across the Maldives, but hopefully the levels of coral mortality will be lower than 2016.
  • The accumulating global ocean heat content has not affected the Indian Ocean region as badly as other parts of the world.
  • It’s possible that the effects of the Indian Ocean Diople (IOD) has dampened the warming El Nino patterns in the region, by bringing increased cloud cover and unusually heavy rainfall (as experienced in the Maldives during May).

Climate Animations (click to play)

Red List of Mangrove Ecosystems (IUCN)

June 2024

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NOAA CoralWatch: Maldives as at 01 June

Copernicus C3S timeseries_era5_sst (2024.05.31)

Copernicus C3S timeseries_era5_sst (2024.05.31)

Copernicus C3S map_era5_2t_percentiles (2024.05.31)

Copernicus C3S map_era5_2t_percentiles (2024.05.31)

Indicators of Global Climate Change 2023 - Forster et al (2024) [essd-16-2625-2024-f11] Copernicus

Indicators of Global Climate Change – Forster et al (2024) – copernicus

Fisheries at depth (Vertical distribution of benthic realms) Jacquemont (2024) Nat Commun

3D ocean assessments: Fisheries reach deep, but marine protection remains shallow – Jacquemont et al (2024) Nat Commun

2024 Ocean Temperatures Fall to 2023 Levels for First Time
A glimmer of good news this month, as global ocean temperatures finally stop breaking all-time records, and fall ever-so slightly below those recorded during 2023. (This could be due to ENSO moving away from El Niño and towards the La Niña phase.)
Despite this good news, it’s important to note that global land/ocean temperatures continue to be elevated, relative to previous decades.

SST Global 2024.06.22 (ERA5 C3S)

SST Global 2024.06.22 (ERA5 C3S)

SST Global 2024.06.25 (NOAA)

SST Global 2024.06.25 (NOAA)

Temperature & Rainfall Forecasts (June-September 2024) – SASCOF-28 and CSUF, Pune, India (April 2024).
Statement [PDF] on the Seasonal Climate Outlook over South Asia for the 2024 Southwest Monsoon Season (June – September)
Forecast for the 2024 SW monsoon season over most parts of the South Asia region:
– Above normal rainfall, along with above normal min-max temperatures

TEMPERATURE-MAX forecast SE Asia (Jun-Sept 2024) [SASCOF, MV-Meteo]

TEMPERATURE forecast SE Asia (Jun-Sept 2024) [SASCOF, MV-Meteo]

RAINFALL forecast SE Asia (Jun-Sept 2024) [SASCOF, MV-Meteo]

RAINFALL forecast SE Asia (Jun-Sept 2024) [SASCOF, MV-Meteo]

July 2024

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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.

SST Global 2024.07.12 (ERA5 C3S)

SST Global 2024.07.12 (ERA5 C3S)

SST Global 2024.07.12 (NOAA)

SST Global 2024.07.12 (NOAA)

NIOsst Indian Ocean SST (2024.07.12) [@DrKimWood]

NIOsst Indian Ocean SST (2024.07.12) [@DrKimWood]

Ghost Gear (Marina Wang, from Richardson 2022) hakaimagazine

Image from: Gluts of Ghost Gear (Hakai Magazine) by Marina Wang, based on: Global estimates of fishing gear lost to the ocean each year (Richardson et al, 2022)
See also: Global Ghost Gear Initiative (GGGI)