Increases In Ocean Temperatures Research Articles

Longer and more frequent marine heatwaves over the past century

Heatwaves are important climatic extremes in atmospheric and oceanic systems that can have devastating and long-term impacts on ecosystems, with subsequent socioeconomic consequences. Recent prominent marine heatwaves have attracted considerable scientific and public interest. Despite this, a comprehensive assessment of how these ocean temperature extremes have been changing globally is missing. Using a range of ocean temperature data including global records of daily satellite observations, daily in situ measurements and gridded monthly in situ-based data sets, we identify significant increases in marine heatwaves over the past century. We find that from 1925 to 2016, global average marine heatwave frequency and duration increased by 34% and 17%, respectively, resulting in a 54% increase in annual marine heatwave days globally. Importantly, these trends can largely be explained by increases in mean ocean temperatures, suggesting that we can expect further increases in marine heatwave days under continued global warming.

Temporal changes in atmospheric water content during the December 2004 Sumatra earthquake as estimated from GPS signals and its possible connection to the January 2005 California flash flood

We studied the temporal change in Zenith Total Delay (ZTD) from the GPS signals received at sites around the epicentral region of the 26 December 2004 Great Sumatra earthquake (Mw 9.0). The estimated ZTD values at the nearest GPS locations available around the earthquake region showed a significant rise after the earthquake at locations to its east (~63mm at NTUS) and south (~110mm at COCO), but no changes were seen towards the west. The increase in ZTD (and thus precipitable water vapor, PWV) associated to the earthquake process is attributed to the thermal energy released through the earthquake process and the probable heat induced on to the ocean surface through the magma upwelling processes in the earthquake region, which all might have caused increase in ocean water temperature and catalyzed the evaporation process yielding high precipitation over the region. However, this high precipitation did not produce rainfall in its vicinity and appears to have moved to the California coast by the subtropical jet stream present over the region during this period. The southern California experienced a historical heavy rain from 28th of December, 2004 to 12th of January, 2005 and the El Niño conditions in the Pacific Ocean alone could not explain such an unusual high precipitation in the winter period. We conclude that the severe weather conditions over the Californian coast and resulting flash flood might have been caused by transport of high water vapor formed over the Sumatra earthquake epicentral region to the California coast by the subtropical jet stream movement from west to east.

A decade of marine mammal acoustical presence and habitat preference in the Bering Sea

As Arctic seas rapidly change with increased ocean temperatures and decreased sea ice extent, traditional marine mammal distributions may be altered, and non-traditional Arctic species may shift poleward. Extant and seasonal continental shelf odontocete species in the Arctic Ocean include sperm whales, killer whales, beluga whales, delphinids, harbour porpoises, and Dall’s porpoises. Until recently, recording constraints limited higher sampling rates, preventing detection of many of these high frequency-producing species in the Arctic seas. Using one of the first long-term data sets to record clicks, buzzes, and whistles, multiple species have been detected and classified to explore shifting distributions in the Arctic Corridor. The data were then paired with environmental variables for generalized linear and additive modeling. Pacific white-sided dolphins were detected for a few years during minimal ice coverage. Dall’s porpoises and Risso’s dolphins may have been acoustically detected in areas farther n...

Large Stimulation of Recalcitrant Dissolved Organic Carbon Degradation by Increasing Ocean Temperatures

More than 96% of organic carbon in the ocean is in the dissolved form, most of it with lifetimes of decades to millennia. Yet, we know very little about the temperature sensitivity of dissolved organic carbon (DOC) degradation in a warming ocean. Combining independent estimates from laboratory experiments, oceanographic cruises and a global ocean DOC cycling model, we assess the relationship between DOC decay constants and seawater temperatures. Our results show that the apparent activation energy of DOC decay (Ea) increases by 3-fold from the labile (lifetime of days) and semi-labile (lifetime of months) to the semi-refractory (lifetime of decades) DOC pools, with only minor differences between the world’s largest ocean basins. This translates into increasing temperature coefficients (Q10) from 1.7–1.8 to 4–8, showing that the generalised assumption of a constant Q10 of ~2 for biological rates is not universally applicable for the microbial degradation of DOC in the ocean. Therefore, rising ocean temperatures will preferentially impact the microbial degradation of the more recalcitrant and larger of the three studied pools. Assuming a uniform 1oC warming scenario throughout the ocean, our model predicts a global decrease of the DOC reservoir by 7 ± 1 Pg C. This represents a 15% reduction of the semi-labile + semi-refractory DOC pools.

A large predatory reef fish species moderates feeding and activity patterns in response to seasonal and latitudinal temperature variation

Climate-driven increases in ocean temperatures are expected to affect the metabolic requirements of marine species substantially. To mitigate the impacts of increasing temperatures in the short-term, it may be necessary for ectothermic organisms to alter their foraging behaviour and activity. Herein, we investigate seasonal variation in foraging behaviour and activity of latitudinally distinct populations of a large coral reef predator, the common coral trout, Plectropomus leopardus, from the Great Barrier Reef, Australia. P. leopardus exhibited increased foraging frequency in summer versus winter time, irrespective of latitude, however, foraging frequency substantially declined at water temperatures >30 °C. Foraging frequency also decreased with body size but there was no interaction with temperature. Activity patterns were directly correlated with water temperature; during summer, the low-latitude population of P. leopardus spent up to 62% of their time inactive, compared with 43% for the high-latitude population. The impact of water temperature on activity patterns was greatest for larger individuals. These results show that P. leopardus moderate their foraging behaviour and activity according to changes in ambient temperatures. It seems likely that increasing ocean temperatures may impose significant constraints on the capacity of large-bodied fishes to obtain sufficient prey resources while simultaneously conserving energy.

기후변화가 대형선망 고등어 어업의 최적탄소배출량에 미치는 영향분석

The purpose of this paper is to estimate the optimal <TEX>$CO_2$</TEX> emission in the maximum economic yield (MEY), maximum sustainable yield (MSY), and open access (OA) using a bioeconomic model. The results are as follows; in the case of <TEX>$E_{MEY}$</TEX>, <TEX>$E_{MSY}$</TEX>, and <TEX>$E_{OA}$</TEX> levels, <TEX>$CO_2$</TEX> emissions are estimated at <TEX>$150,704,746CO_2/kg$</TEX>, <TEX>$352,211,193CO_2/kg$</TEX>, and <TEX>$301,409,492CO_2/kg$</TEX> respectively. We show that the <TEX>$E_{MEY}$</TEX> is more efficient than the other levels. That is, the level of <TEX>$E_{MEY}$</TEX> signifies the optimal economic fishing usage as the most economically efficient usage for large purse seine fishery catching mackerel species. The emission of <TEX>$CO_2$</TEX> in <TEX>$E_{MEY}$</TEX> is the lowest level. Also, the impacts of climate changes such as ocean temperature increase, ocean acidification, and the combined impact thereof show that the biomass of mackerel decreases.

Small ocean temperature increases elicit stage-dependent changes in DNA methylation and gene expression in a fish, the European sea bass

In natural fish populations, temperature increases can result in shifts in important phenotypic traits. DNA methylation is an epigenetic mechanism mediating phenotypic changes. However, whether temperature increases of the magnitude predicted by the latest global warming models can affect DNA methylation is unknown. Here, we exposed European sea bass to moderate temperature increases in different periods within the first two months of age. We show that increases of even 2 °C in larvae significantly changed global DNA methylation and the expression of ecologically-relevant genes related to DNA methylation, stress response, muscle and organ formation, while 4 °C had no effect on juveniles. Furthermore, DNA methylation changes were more marked in larvae previously acclimated to a different temperature. The expression of most genes was also affected by temperature in the larvae but not in juveniles. In conclusion, this work constitutes the first study of DNA methylation in fish showing that temperature increases of the magnitude predicted by the latest global warming models result in stage-dependent alterations in global DNA methylation and gene expression levels. This study, therefore, provides insights on the possible consequences of climate change in fish mediated by genome-wide epigenetic modifications.

Trends in summer bottom-water temperatures on the northern Gulf of Mexico continental shelf from 1985 to 2015

We quantified trends in the 1985 to 2015 summer bottom-water temperature on the northern Gulf of Mexico (nGOM) continental shelf for data collected at 88 stations with depths ranging from 3 to 63 m. The analysis was supplemented with monthly data collected from 1963 to 1965 in the same area. The seasonal summer peak in average bottom-water temperature varied concurrently with air temperature, but with a 2- to 5-month lag. The summer bottom-water temperature declined gradually with depth from 30 oC at stations closest to the shore, to 20 oC at the offshore edge of the study area, and increased an average 0.051 oC y-1 between1963 and 2015. The bottom-water warming in summer for all stations was 1.9 times faster compared to the rise in local summer air temperatures, and 6.4 times faster than the concurrent increase in annual global ocean sea surface temperatures. The annual rise in average summer bottom-water temperatures on the subtropical nGOM continental shelf is comparable to the few published temperature trend estimates from colder environments. These recent changes in the heat storage on the nGOM continental shelf will affect oxygen and carbon cycling, spatial distribution of fish and shrimp, and overall species diversity.

Facing the future: Conservation as a precursor for building coastal territorial cohesion and resilience

Abstract On a global scale, most of the coastal zones in the world are undergoing rapid and accelerating changes. This coastal syndrome combines two major trends: one linked to the growth of coastal populations, habitat, transport and industrial infrastructures (assets); the other linked to the influence of climate change and its effects in terms of sea‐level rise, increased frequency of extreme weather events, acidification and increase in ocean surface temperature, both affecting the health of coastal ecosystems. This situation is also reflected in the increase in coastal engineering solutions, which have significant impacts on coastal hydrodynamics and natural ecosystems. This extremely dynamic context calls for an evolution in conservation and spatial planning strategies in order to better anticipate changes that may affect not only the sustainability of both the distribution and health of natural ecosystems, but also the relevance of conservation efforts. Marine and coastal protected areas help preserve ecological services, and reduce the risks faced by coastal communities. Therefore, it can be argued that the effectiveness of these conservation units will depend on the ability, (i) to take into account their territorial context, and also (ii) to base the management decisions on a prospective and sufficiently anticipated (future‐oriented) approach. MPA management must be proactive to cope with such rapid changes. The Nexus approach, promoted by the IUCN Commission on Ecosystem Management ‐ coastal ecosystem group (CEM/CEG), places marine and coastal spatial planning as a key integrative element linking conservation, adaptation to climate change and coastal risk reduction, and as a part of no‐regret adaptation strategies. This paper highlights the main factors that characterize current coastal dynamics, and then briefly presents three future‐oriented pilot operations, implemented in Western Africa at different scales. These operations illustrate how MPAs must become structuring elements for the organization and development of coastal territories if they are to contribute to the resilience of coastal systems and to ensure their own long‐term sustainability.

Marine growth patterns of southern British Columbia chum salmon explained by interactions between density-dependent competition and changing climate

Thirty-nine years of scale growth measurements from Big Qualicum River chum salmon (Oncorhynchus keta) in southern British Columbia demonstrated that competition and climate variation affect marine growth and age-at-maturity. A longitudinal study design that accounted for correlation among individuals revealed growth at all ages was reduced when the biomass of North American chum, sockeye (Oncorhynchus nerka), and pink salmon (Oncorhynchus gorbuscha) was high. When North Pacific Gyre Oscillation (NPGO) was positive, indicating increased primary productivity, predicted growth increased. Climate variation influenced competition effects. For instance, density-dependent competition effects increased when NPGO became more positive and Pacific Decadal Oscillation became more negative (indicating cool conditions), causing the greatest range in predicted scale size. Chum salmon are likely to exhibit continued reduction in growth at age due to increased ocean temperatures driven by climate change and high aggregate salmon biomass that includes hatchery releases. If evidence of biomass and climate effects presented here are common among Pacific salmon populations, reduction of hatchery releases should be considered.

Potential influence of a marine heatwave on range extensions of tropical fishes in the eastern Indian Ocean—Invaluable contributions from amateur observers

Global changes to fish distributions are expected to continue in coming decades with predicted increases in ocean temperatures and the frequency of extreme climatic events. In the eastern Indian Ocean during the 2010/11 summer, sea surface temperatures 4–5 °C above average and an unseasonal, anomalously strong, Leeuwin Current (LC) triggered a “marine heatwave” along the west coast of Australia, with elevated water temperatures persisting for a further two years. Peak LC flows in summer/autumn transported pelagic early life history stages of summer-spawning coastal subtropical and tropical fishes southwards. This study examined whether the heatwave enabled the arrival, persistence and reproduction of such species in waters ≥∼32°S using a range of available datasets. Juveniles of Chaetodon assarius, Trachinotus botla, T. baillonii, Polydactylus plebeius, Psammoperca waigiensis and Siganus sp. recruited into nearshore waters at ≥∼32°S in 2011. Polydactylus plebeius survived until the summer of 2012/13. Trachinotus spp., P. waigiensis and Siganus sp. survived over consecutive winters, with Siganus sp. establishing a self-recruiting, breeding population two years later. A return to more typical summer water temperatures by 2013/14 was associated with an apparent recruitment failure of Siganus sp. This is a rare example of a tropical vagrant surviving to breed in temperate regions. Confirmation of range extension beyond existing limits of this and other tropical species will be primarily dependent on either continuous or intermittent recruitment from this recently established southern breeding population. Commercial fisheries catch and effort data were of limited use in this study because they were not designed to record small catches of unusual and/or non-target species. In contrast, fisheries-independent recruitment surveys recorded tropical juveniles and validated amateur observations provided important information on unusual species. The study confirmed the emerging contribution of ‘citizen scientists’ working with researchers to document climate related impacts in the marine environment.

Assessing the ecosystem-level consequences of a small-scale artisanal kelp fishery within the context of climate-change.

Coastal communities worldwide rely on small-scale artisanal fisheries as a means of increasing food security and alleviating poverty. Even small-scale fishing activities, however, are prone to resource depletion and environmental degradation, which can erode livelihoods in the long run. Thus, there is a pressing need to identify viable and resilient artisanal fisheries, and generate knowledge to support management within the context of a rapidly changing climate. We examined the ecosystem-level consequences of an artisanal kelp fishery (Macrocystis pyrifera), finding small-scale harvest of this highly productive species poses minimal impacts on kelp recovery rates, survival, and biomass dynamics, and abundances of associated commercial and culturally important fish species. These results suggest that small-scale harvest poses minimal trade-offs for the other economic benefits provided by these ecosystems, and their inherent, spiritual, and cultural value to humans. However, we detected a negative impact of warmer seawater temperatures on kelp recovery rates following harvest, indicating that the viability of harvest, even at small scales, may be threatened by future increases in global ocean temperature. This suggests that negative impacts of artisanal fisheries may be more likely to arise in the context of a warming climate, further highlighting the widespread effects of global climate change on coastal fisheries and livelihoods.

Impact of the GeoMIP G1 sunshade geoengineering experiment on the Atlantic meridional overturning circulation

We analyze the multi-earth system model responses of ocean temperatures and the Atlantic Meridional Overturning Circulation (AMOC) under an idealized solar radiation management scenario (G1) from the Geoengineering Model Intercomparison Project. All models simulate warming of the northern North Atlantic relative to no geoengineering, despite geoengineering substantially offsetting the increases in mean global ocean temperatures. Increases in the temperature of the North Atlantic Ocean at the surface (∼0.25 K) and at a depth of 500 m (∼0.10 K) are mainly due to a 10 Wm−2 reduction of total heat flux from ocean to atmosphere. Although the AMOC is slightly reduced under the solar dimming scenario, G1, relative to piControl, it is about 37% stronger than under abrupt4 × CO2. The reduction of the AMOC under G1 is mainly a response to the heat flux change at the northern North Atlantic rather than to changes in the water flux and the wind stress. The AMOC transfers heat from tropics to high latitudes, helping to warm the high latitudes, and its strength is maintained under solar dimming rather than weakened by greenhouse gas forcing acting alone. Hence the relative reduction in high latitude ocean temperatures provided by solar radiation geoengineering, would tend to be counteracted by the correspondingly active AMOC circulation which furthermore transports warm surface waters towards the Greenland ice sheet, warming Arctic sea ice and permafrost.

Limited capacity for developmental thermal acclimation in three tropical wrasses

For effective conservation and management of marine systems, it is essential that we understand the biological impacts of and capacity for acclimation to increased ocean temperatures. This study investigated for the first time the effects of developing in projected warmer ocean conditions in the tropical wrasse species: Halichoeres melanurus, Halichoeres miniatus and Thalassoma amblycephalum. New recruits were reared for 11 weeks in control (29 °C) and +2 °C (31 °C) temperature treatments, consistent with predicted increases in sea surface temperature by 2100. A broad range of key attributes and performance parameters was tested, including aerobic metabolism, swimming ability, burst escape performance and physical condition. Response latency of burst performance was the only performance parameter in which evidence of beneficial thermal developmental acclimation was found, observed only in H. melanurus. Generally, development in the +2 °C treatment came at a significant cost to all species, resulting in reduced growth and physical condition, as well as metabolic and swimming performance relative to controls. Development in +2 °C conditions exacerbated the effects of warming on aerobic metabolism and swimming ability, compared to short-term warming effects. Burst escape performance parameters were only mildly affected by development at +2 °C, with non-locomotor performance (response latency) showing greater thermal sensitivity than locomotor performance parameters. These results indicate that the effects of future climate change on tropical wrasses would be underestimated with short-term testing. This study highlights the importance of holistic, longer-term developmental experimental approaches, with warming found to yield significant, species-specific responses in all parameters tested.

The most primitive metazoan animals, the placozoans, show high sensitivity to increasing ocean temperatures and acidities.

The increase in atmospheric carbon dioxide (CO2) leads to rising temperatures and acidification in the oceans, which directly or indirectly affects all marine organisms, from bacteria to animals. We here ask whether the simplest—and possibly also the oldest—metazoan animals, the placozoans, are particularly sensitive to ocean warming and acidification. Placozoans are found in all warm and temperate oceans and are soft‐bodied, microscopic invertebrates lacking any calcified structures, organs, or symmetry. We here show that placozoans respond highly sensitive to temperature and acidity stress. The data reveal differential responses in different placozoan lineages and encourage efforts to develop placozoans as a potential biomarker system.

New and historical records of the ocean sunfish Mola mola in Icelandic waters.

The ocean sunfish Mola mola is considered to be globally distributed in both temperate and tropical waters, but there are many gaps in the knowledge of this species' distribution. A total of 31 records of M. mola from Icelandic waters, dating from 1845 to 2014, are presented and georeferenced. An increase in the number of records at the beginning of this century and particularly in 2012, is suggested to be a consequence of both an increase in ocean temperature on the Icelandic shelf and changes in large scale temperature variations in the North Atlantic Ocean.

No effect of high pCO2 on juvenile blue crab, Callinectes sapidus, growth and consumption despite positive responses to concurrent warming

Future climate scenarios predict increases in both ocean temperature and dissolved carbon dioxide (pCO2) over the next century. Calcifying invertebrates, which depend on specific conditions of temperature and carbonate chemistry for many processes, may be especially affected by these changes. In our study, juvenile blue crab, Callinectes sapidus, were exposed to one of four temperature/pCO2 treatments (ambient/low, ambient/high, high/low, and high/high) for two complete molts. Our study is the first to examine the effect of multiple climate stressors on blue crab and therefore basic responses, including the growth per molt (GPM), inter-molt period (IMP), and food consumption, were quantified. GPM was not affected by either increased temperature or pCO2. Although increased pCO2 did not significantly influence the duration of crab IMP, crabs in warm water had significantly shorter IMP (10.6 ± 3.1 days (± SD)) than crabs in ambient water (12.5 ± 2.8 days). Increased pCO2 did not significantly affect the amount of food crabs consumed, but crabs in warm water ate significantly more food than those in ambient water. These data suggest that the impact of warming outweighs the impact of acidification in juvenile blue crab. The effects of these changes on more complex physiological parameters such as metabolism and carapace chemistry remain to be examined. Additionally, quantifying the changes to the Chesapeake Bay food web that may occur due to the observed increase in crab growth and consumption is important to ensure sustainability of this resource in the face of future climatic changes.

A preliminary acoustic survey of echolocating marine mammals in the Bering Sea

As the Arctic seas rapidly change with increased ocean temperatures and decreased sea ice extent, traditional Arctic marine mammal distributions will be altered, and non-traditionally Arctic species may shift poleward. Arctic species typically include sperm, bowhead, humpback, right, gray, fin, and blue whales; odontocetes, specifically killer and beluga whales; and several pinnipeds species. Their acoustic presence has been documented because they produce relatively low-frequency sounds that are detectable by many common, remotely-deployed recording platforms. Until recently, however, recording constraints of power and storage limited higher sampling rates and prevented the detection of many high-frequency-producing species in the Arctic seas. Such species likely include Baird’s, Cuvier’s, and Stejneger’s beaked whales, as well as Northern right whale and Pacific white-sided dolphins. Using one of the first long-term data sets to record relatively high frequencies in the Bering Sea, signal types similar ...

A change in coral extension rates and stable isotopes after El Niño-induced coral bleaching and regional stress events.

Coral reefs are biologically diverse ecosystems threatened with effective collapse under rapid climate change, in particular by recent increases in ocean temperatures. Coral bleaching has occurred during major El Niño warming events, at times leading to the die-off of entire coral reefs. Here we present records of stable isotopic composition, Sr/Ca ratios and extension rate (1940–2004) in coral aragonite from a northern Venezuelan site, where reefs were strongly impacted by bleaching following the 1997–98 El Niño. We assess the impact of past warming events on coral extension rates and geochemical proxies. A marked decrease in coral (Pseudodiploria strigosa) extension rates coincides with a baseline shift to more negative values in oxygen and carbon isotopic composition after 1997–98, while a neighboring coral (Siderastrea siderea) recovered to pre-bleaching extension rates simultaneously. However, other stressors, besides high temperature, might also have influenced coral physiology and geochemistry. Coastal Venezuelan reefs were exposed to a series of extreme environmental fluctuations since the mid-1990s, i.e. upwelling, extreme rainfall and sediment input from landslides. This work provides important new data on the potential impacts of multiple regional stress events on coral isotopic compositions and raises questions about the long-term influence on coral-based paleoclimate reconstructions.

Projected changes of Antarctic krill habitat by the end of the 21st century

AbstractClimate change is rapidly shaping the living environment of the most abundant keystone species of the Antarctic marine food web, Antarctic krill. Projected future changes for the krill habitat include a sustained increase in ocean temperature and changes in sea ice and chlorophyll a. Here we investigate how these factors affect the early life history of krill and identify the regions around Antarctica where the impact will be greatest. Our tool is a temperature‐dependent krill growth model forced by data from comprehensive greenhouse warming simulations. We find that by the year 2100 localized regions along the western Weddell Sea, isolated areas of the Indian Antarctic , and the Amundsen/Bellingshausen Sea will support successful spawning habitats for krill. The failure of potentially successful spawning will have a strong impact on the already declining adult populations with consequences for the Antarctic marine food web, having both ecological and commercial ramifications.