Global Oceans

Global Oceans is one chapter from the State of the Climate in 2019 annual report and is avail-able from https://doi.org/10.1175/BAMS-D-20-0105.1. Compiled by NOAA’s National Centers for Environmental Information, State of the Climate in 2019 is based on contr1ibutions from scien-tists from around the world. It provides a detailed update on global climate indicators, notable weather events, and other data collected by environmental monitoring stations and instru-ments located on land, water, ice, and in space. The full report is available from https://doi.org /10.1175/2020BAMSStateoftheClimate.1

State of the climate in 2018

In 2018, the dominant greenhouse gases released into Earth’s atmosphere—carbon dioxide, methane, and nitrous oxide—continued their increase. The annual global average carbon dioxide concentration at Earth’s surface was 407.4 ± 0.1 ppm, the highest in the modern instrumental record and in ice core records dating back 800 000 years. Combined, greenhouse gases and several halogenated gases contribute just over 3 W m−2 to radiative forcing and represent a nearly 43% increase since 1990. Carbon dioxide is responsible for about 65% of this radiative forcing. With a weak La Niña in early 2018 transitioning to a weak El Niño by the year’s end, the global surface (land and ocean) temperature was the fourth highest on record, with only 2015 through 2017 being warmer. Several European countries reported record high annual temperatures. There were also more high, and fewer low, temperature extremes than in nearly all of the 68-year extremes record. Madagascar recorded a record daily temperature of 40.5°C in Morondava in March, while South Korea set its record high of 41.0°C in August in Hongcheon. Nawabshah, Pakistan, recorded its highest temperature of 50.2°C, which may be a new daily world record for April. Globally, the annual lower troposphere temperature was third to seventh highest, depending on the dataset analyzed. The lower stratospheric temperature was approximately fifth lowest. The 2018 Arctic land surface temperature was 1.2°C above the 1981–2010 average, tying for third highest in the 118-year record, following 2016 and 2017. June’s Arctic snow cover extent was almost half of what it was 35 years ago. Across Greenland, however, regional summer temperatures were generally below or near average. Additionally, a satellite survey of 47 glaciers in Greenland indicated a net increase in area for the first time since records began in 1999. Increasing permafrost temperatures were reported at most observation sites in the Arctic, with the overall increase of 0.1°–0.2°C between 2017 and 2018 being comparable to the highest rate of warming ever observed in the region. On 17 March, Arctic sea ice extent marked the second smallest annual maximum in the 38-year record, larger than only 2017. The minimum extent in 2018 was reached on 19 September and again on 23 September, tying 2008 and 2010 for the sixth lowest extent on record. The 23 September date tied 1997 as the latest sea ice minimum date on record. First-year ice now dominates the ice cover, comprising 77% of the March 2018 ice pack compared to 55% during the 1980s. Because thinner, younger ice is more vulnerable to melting out in summer, this shift in sea ice age has contributed to the decreasing trend in minimum ice extent. Regionally, Bering Sea ice extent was at record lows for almost the entire 2017/18 ice season. For the Antarctic continent as a whole, 2018 was warmer than average. On the highest points of the Antarctic Plateau, the automatic weather station Relay (74°S) broke or tied six monthly temperature records throughout the year, with August breaking its record by nearly 8°C. However, cool conditions in the western Bellingshausen Sea and Amundsen Sea sector contributed to a low melt season overall for 2017/18. High SSTs contributed to low summer sea ice extent in the Ross and Weddell Seas in 2018, underpinning the second lowest Antarctic summer minimum sea ice extent on record. Despite conducive conditions for its formation, the ozone hole at its maximum extent in September was near the 2000–18 mean, likely due to an ongoing slow decline in stratospheric chlorine monoxide concentration. Across the oceans, globally averaged SST decreased slightly since the record El Niño year of 2016 but was still far above the climatological mean. On average, SST is increasing at a rate of 0.10° ± 0.01°C decade−1 since 1950. The warming appeared largest in the tropical Indian Ocean and smallest in the North Pacific. The deeper ocean continues to warm year after year. For the seventh consecutive year, global annual mean sea level became the highest in the 26-year record, rising to 81 mm above the 1993 average. As anticipated in a warming climate, the hydrological cycle over the ocean is accelerating: dry regions are becoming drier and wet regions rainier. Closer to the equator, 95 named tropical storms were observed during 2018, well above the 1981–2010 average of 82. Eleven tropical cyclones reached Saffir–Simpson scale Category 5 intensity. North Atlantic Major Hurricane Michael’s landfall intensity of 140 kt was the fourth strongest for any continental U.S. hurricane landfall in the 168-year record. Michael caused more than 30 fatalities and $25 billion (U.S. dollars) in damages. In the western North Pacific, Super Typhoon Mangkhut led to 160 fatalities and$6 billion (U.S. dollars) in damages across the Philippines, Hong Kong, Macau, mainland China, Guam, and the Northern Mariana Islands. Tropical Storm Son-Tinh was responsible for 170 fatalities in Vietnam and Laos. Nearly all the islands of Micronesia experienced at least moderate impacts from various tropical cyclones. Across land, many areas around the globe received copious precipitation, notable at different time scales. Rodrigues and Réunion Island near southern Africa each reported their third wettest year on record. In Hawaii, 1262 mm precipitation at Waipā Gardens (Kauai) on 14–15 April set a new U.S. record for 24-h precipitation. In Brazil, the city of Belo Horizonte received nearly 75 mm of rain in just 20 minutes, nearly half its monthly average. Globally, fire activity during 2018 was the lowest since the start of the record in 1997, with a combined burned area of about 500 million hectares. This reinforced the long-term downward trend in fire emissions driven by changes in land use in frequently burning savannas. However, wildfires burned 3.5 million hectares across the United States, well above the 2000–10 average of 2.7 million hectares. Combined, U.S. wildfire damages for the 2017 and 2018 wildfire seasons exceeded $40 billion (U.S. dollars)

The 2020 report of The Lancet Countdown on health and climate change: responding to converging crises

The Lancet Countdown is an international collaboration, established to provide an independent, global monitoring system dedicated to tracking the emerging health profile of the changing climate. The 2020 report presents 43 indicators across five sections: climate change impacts, exposures, and vulnerability; adaptation, planning, and resilience for health; mitigation actions and health co-benefits; economics and finance; and public and political engagement. This report represents the findings and consensus of the 35 leading academic institutions and UN agencies that make up the Lancet Countdown, and draws on the expertise of climate scientists, geographers, and engineers; of energy, food, and transport experts; and of economists, social and political scientists, data scientists, public health professionals, and doctors

Large decadal changes in air-sea CO2 fluxes in the Caribbean Sea

Sixteen years of surface water CO2 data from autonomous systems on cruise ships sailing in the Caribbean Sea and Western North Atlantic show marked changes on interannual timescales. The measured changes in fugacity (≈partial pressure) of CO2 in surface water, fCO2w, are based on over a million observations. Seasonally the patterns are similar to other oligotrophic subtropical regions with an amplitude of fCO2w of ≈40 μatm with low wintertime values, causing the area to be a sink, and high summertime values making it a source of CO2 to the atmosphere. On annual scales there was negligible increase of fCO2w from 2002 to 2010 and a rapid increase from 2010 to 2018. Correspondingly, the trend of air‐sea CO2 flux from 2002 to 2010 was strongly negative (increasing uptake or sink) at −0.05 ± 0.01 (mol m−2 year−1) year−1 and positive (decreasing uptake) at 0.02 ± 0.02 (mol m−2 year−1) year−1 from 2010‐2018. For the whole period from 2002 to 2018, the fCO2w lagged the atmospheric CO2 increase by 24 %, causing an increase in CO2 uptake. The average flux into the ocean for the 16 years is −0.20 ± 0.16 mol m−2 year−1 with the uncertainty reflecting the standard deviation in annual means. The change in multiannual trend in fCO2w is modulated by several factors, notably changes in sea surface temperature and ocean mixed layer depth that, in turn, affected the physical and biological processes controlling fCO2w

Sea temperature influences accumulation of tetrodotoxin in British bivalve shellfish

Tetrodotoxin (TTX), a potent neurotoxin mostly associated with pufferfish poisoning, is also found in bivalve shellfish. Recent studies into this emerging food safety threat reported TTX in a few, mainly estuarine, shellfish production areas in some European countries, including the United Kingdom. A pattern in occurrences has started to emerge, however the role of temperature on TTX has not been investigated in detail. Therefore, we conducted a large systematic TTX screening study, encompassing over 3500 bivalve samples collected throughout 2016 from 155 shellfish monitoring sites along the coast of Great Britain. Overall, we found that only 1.1 % of tested samples contained TTX above the reporting limit of 2 μg/kg whole shellfish flesh and these samples all originated from ten shellfish production sites in southern England. Subsequent continuous monitoring of selected areas over a five-year period showed a potential seasonal TTX accumulation in bivalves, starting in June when water temperatures reached around 15 °C. For the first time, satellite-derived data were also applied to investigate temperature differences between sites with and without confirmed presence of TTX in 2016. Although average annual temperatures were similar in both groups, daily mean values were higher in summer and lower in winter at sites where TTX was found. Here, temperature also increased significantly faster during late spring and early summer, the critical period for TTX. Our study supports the hypothesis that temperature is one of the key triggers of events leading to TTX accumulation in European bivalves. However, other factors are also likely to play an important role, including the presence or absence of a de novo biological source, which remains elusive

DataSheet_1_Surface ocean warming near the core of hurricane Sam and its representation in forecast models.docx

On September 30, 2021, a saildrone uncrewed surface vehicle intercepted Hurricane Sam in the northwestern tropical Atlantic and provided continuous observations near the eyewall. Measured surface ocean temperature unexpectedly increased during the first half of the storm. Saildrone current shear and upper-ocean structure from the nearest Argo profiles show an initial trapping of wind momentum by a strong halocline in the upper 30 m, followed by deeper mixing and entrainment of warmer subsurface water into the mixed layer. The ocean initial conditions provided to operational forecast models failed to capture the observed upper-ocean structure. The forecast models failed to simulate the warming and developed a surface cold bias of ~0.5°C by the time peak winds were observed, resulting in a 12-17% underestimation of surface enthalpy flux near the eyewall. Results imply that enhanced upper-ocean observations and, critically, improved assimilation into the hurricane forecast systems, could directly benefit hurricane intensity forecasts.</p

State of the climate in 2020, Global Oceans

Global Oceans is one chapter from the State of the Climate in 2020 annual report and is available from https://doi.org/10.1175/BAMS-D-21-0083.1. Compiled by NOAA’s National Centers for Environmental Information, State of the Climate in 2020 is based on contributions from scientists from around the world. It provides a detailed update on global climate indicators, notable weather events, and other data collected by environmental monitoring stations and instruments located on land, water, ice, and in space. The full report is available from https://doi.org/10.1175/2021BAMSStateoftheClimate.

Global Oceans

The Atlantic meridional overturning circulation (MOC) and heat transport (MHT) have been observed (Fig. 3.21) at several trans-basin and western boundary moored arrays (e.g., Frajka-Williams et al. 2019; Berx et al. 2021; Hummels et al. 2022), as well as by synthesizing in situ and satellite altimetry measurements at several latitudes (Hobbs and Willis 2012; Sanchez-Franks et al. 2021; Dong et al. 2021; Kersalé et al. 2021). Here we provide updates on the MOC and MHT estimates from the Rapid Climate Change/MOC and Heatflux Array/Western Boundary Time Series (RAPID-MOCHA-WBTS) moored array at 26.5°N and from the synthetic approach at 41°N and at several latitudes in the South Atlantic. While updates for the Overturning in the Subpolar North Atlantic Program and the South Atlantic MOC Basin-wide Array at 34.5°S are pending, we report on recent advances in observing the variability of flows comprising the lower limb of the North Atlantic MOC, including the Meridional Overturning Variability Experiment (MOVE, 16°N)