Climate Change, Ocean Acidification, and Ocean Warming

Sea-ice response to climate change in the Bering Sea during the Mid-Pleistocene Transition

Worne S, Stroynowski Z, Kender S, Swann GEA. Sea-ice response to climate change in the Bering Sea during the Mid-Pleistocene Transition. Quaternary Science Reviews [Internet]. 2021 ;259:106918. Available from: https://www.sciencedirect.com/science/article/pii/S0277379121001256?dgcid=raven_sd_search_email
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Sea-ice is believed to be an important control on climatic changes through the Mid-Pleistocene Transition (MPT; 0.6–1.2 Ma). However, the low resolution/short timescale of existing reconstructions prevents a full evaluation of these dynamics. Here, diatom assemblages from the Bering Sea are used to investigate sea-ice evolution on millennial timescales. We find that sea-ice was primarily controlled by ice-sheet/sea level fluctuations that modulated warm water flow into the Bering Sea. Facilitated by an amplified Walker circulation, sea-ice expansion began at ∼1.05 Ma with a step-increase during the 900 kyr event. Maximal pack ice was simultaneous with glacial maxima, suggesting sea-ice was responding to, rather than modulating ice-sheet dynamics, as proposed by the sea-ice switch hypothesis. Significant pack ice, coupled with Bering Strait closure at 0.9 Ma, indicates that brine rejection played an integral role in the glacial expansion/deglacial collapse of intermediate waters during the MPT, regulating subarctic ocean-atmospheric exchanges of CO2.

Key climate change stressors of marine ecosystems along the path of the East African coastal current

Jacobs ZL, Yool A, Jebri F, Srokosz M, van Gennip S, Kelly SJ, Roberts M, Sauer W, Queirós AM, Osuka KE, et al. Key climate change stressors of marine ecosystems along the path of the East African coastal current. Ocean & Coastal Management [Internet]. 2021 ;208:105627. Available from: https://www.sciencedirect.com/science/article/pii/S0964569121001125?dgcid=raven_sd_search_email
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

For the countries bordering the tropical Western Indian Ocean (TWIO), living marine resources are vital for food security. However, this region has largely escaped the attention of studies investigating potential impacts of future climate change on the marine environment. Understanding how marine ecosystems in coastal East Africa may respond to various climatic stressors is vital for the development of conservation and other ocean management policies that can help to adapt to climate change impacts on natural and associated human systems. Here, we use a high-resolution (1/4°) ocean model, run under a high emission scenario (RCP 8.5) until the end of the 21st century, to identify key regionally important climate change stressors over the East African Coastal Current (EACC) that flows along the coasts of Kenya and Tanzania. We also discuss these stressors in the context of projections from lower resolution CMIP5 models. Our results indicate that the main drivers of dynamics and the associated ecosystem response in the TWIO are different between the two monsoon seasons. Our high resolution model projects weakening of the Northeast monsoon (December–February) winds and slight strengthening of the Southeast monsoon (May–September) winds throughout the course of the 21st century, consistent with CMIP5 models. The projected shallower mixed layers and weaker upwelling during the Northeast Monsoon considerably reduce the availability of surface nutrients and primary production. Meanwhile, primary production during the Southeast monsoon is projected to be relatively stable until the end of the century. In parallel, a widespread warming of up to 5 °C is projected year-round with extreme events such as marine heatwaves becoming more intense and prolonged, with the first year-long event projected to occur as early as the 2030s. This extreme warming will have significant consequences for both marine ecosystems and the coastal populations dependent on these marine resources. These region-specific stressors highlight the importance of dynamic ocean features such as the upwelling systems associated with key ocean currents. This indicates the need to develop and implement a regional system that monitors the anomalous behaviour of such regionally important features. Additionally, this study draws attention to the importance of investment in decadal prediction methods, including high resolution modelling, that can provide information at time and space scales that are more directly relevant to regional management and policy making.

Key climate change stressors of marine ecosystems along the path of the East African coastal current

Jacobs ZL, Yool A, Jebri F, Srokosz M, van Gennip S, Kelly SJ, Roberts M, Sauer W, Queirós AM, Osuka KE, et al. Key climate change stressors of marine ecosystems along the path of the East African coastal current. Ocean & Coastal Management [Internet]. 2021 ;208:105627. Available from: https://www.sciencedirect.com/science/article/pii/S0964569121001125?dgcid=raven_sd_search_email
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

For the countries bordering the tropical Western Indian Ocean (TWIO), living marine resources are vital for food security. However, this region has largely escaped the attention of studies investigating potential impacts of future climate change on the marine environment. Understanding how marine ecosystems in coastal East Africa may respond to various climatic stressors is vital for the development of conservation and other ocean management policies that can help to adapt to climate change impacts on natural and associated human systems. Here, we use a high-resolution (1/4°) ocean model, run under a high emission scenario (RCP 8.5) until the end of the 21st century, to identify key regionally important climate change stressors over the East African Coastal Current (EACC) that flows along the coasts of Kenya and Tanzania. We also discuss these stressors in the context of projections from lower resolution CMIP5 models. Our results indicate that the main drivers of dynamics and the associated ecosystem response in the TWIO are different between the two monsoon seasons. Our high resolution model projects weakening of the Northeast monsoon (December–February) winds and slight strengthening of the Southeast monsoon (May–September) winds throughout the course of the 21st century, consistent with CMIP5 models. The projected shallower mixed layers and weaker upwelling during the Northeast Monsoon considerably reduce the availability of surface nutrients and primary production. Meanwhile, primary production during the Southeast monsoon is projected to be relatively stable until the end of the century. In parallel, a widespread warming of up to 5 °C is projected year-round with extreme events such as marine heatwaves becoming more intense and prolonged, with the first year-long event projected to occur as early as the 2030s. This extreme warming will have significant consequences for both marine ecosystems and the coastal populations dependent on these marine resources. These region-specific stressors highlight the importance of dynamic ocean features such as the upwelling systems associated with key ocean currents. This indicates the need to develop and implement a regional system that monitors the anomalous behaviour of such regionally important features. Additionally, this study draws attention to the importance of investment in decadal prediction methods, including high resolution modelling, that can provide information at time and space scales that are more directly relevant to regional management and policy making.

Disentangling the Influence of Three Major Threats on the Demography of an Albatross Community

Cleeland JB, Pardo D, Raymond B, Tuck GN, McMahon CR, Phillips RA, Alderman R, Lea M-A, Hindell MA. Disentangling the Influence of Three Major Threats on the Demography of an Albatross Community. Frontiers in Marine Science [Internet]. 2021 ;8. Available from: https://www.frontiersin.org/articles/10.3389/fmars.2021.578144/full?utm_source=F-AAE&utm_medium=EMLF&utm_campaign=MRK_1585058_45_Marine_20210325_arts_A
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Climate change, fisheries and invasive species represent three pervasive threats to seabirds, globally. Understanding the relative influence and compounding nature of marine and terrestrial threats on the demography of seabird communities is vital for evidence-based conservation. Using 20 years of capture-mark-recapture data from four sympatric species of albatross (black-browed Thalassarche melanophris, gray-headed T. chrysostoma, light-mantled Phoebetria palpebrata and wandering Diomedea exulans) at subantarctic Macquarie Island, we quantified the temporal variability in survival, breeding probability and success. In three species (excluding the wandering albatross because of their small population), we also assessed the influence of fisheries, oceanographic and terrestrial change on these rates. The Southern Annular Mode (SAM) explained 20.87–29.38% of the temporal variability in survival in all three species and 22.72–28.60% in breeding success for black-browed and gray-headed albatross, with positive SAM events related to higher success. The El Niño Southern Oscillation (ENSO) Index explained 21.14–44.04% of the variability in survival, with higher survival rates following La Niña events. For black-browed albatrosses, effort in south-west Atlantic longline fisheries had a negative relationship with survival and explained 22.75–32.21% of the variability. Whereas increased effort in New Zealand trawl fisheries were related to increases in survival, explaining 21.26–28.29 % of variability. The inclusion of terrestrial covariates, reflecting extreme rainfall events and rabbit-driven habitat degradation, explained greater variability in trends breeding probability than oceanographic or fisheries covariates for all three species. These results indicate managing drivers of demographic trends that are most easily controlled, such as fisheries and habitat degradation, will be a viable option for some species (e.g., black-browed albatross) but less effective for others (e.g., light-mantled albatross). Our results illustrate the need to integrate fisheries, oceanographic and terrestrial processes when assessing demographic variability and formulating the appropriate management response.

Coastlines, Coastal Cities, and Climate Change: A Perspective on Urgent Research Needs in the United States

Sandifer PA, Scott GI. Coastlines, Coastal Cities, and Climate Change: A Perspective on Urgent Research Needs in the United States. Frontiers in Marine Science [Internet]. 2021 ;8. Available from: https://www.frontiersin.org/articles/10.3389/fmars.2021.631986/full?utm_source=F-AAE&utm_medium=EMLF&utm_campaign=MRK_1585058_45_Marine_20210325_arts_A
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

This paper builds upon Friedman et al. (2020) and other reviews and statements but provides an explicit focus on research needed to improve the resilience and survivability of coastal communities as they face existential threats from climate change. It does not attempt a prescriptive analysis of potential research emphases, but instead recommends some key research areas that we believe will help provide a solid foundation for community adaptation. Our perspective is based on our experiences over a combined nearly 95 years of work in research, management, and policy, much of it related to coastal environments and their communities, rather than expert deliberation within a large group or a systematic review. We present a list of 25 research priorities binned into 12 categories and targeted to leaders of coastal communities, interested researchers, funders, students, and the public. These priorities are intended to help start more discussion of research needs with and within communities, and help focus attention of researchers on actions that have potential to identify critical decision points and make positive differences for communities. We conclude that priority research should be undertaken with urgency and a much greater level of trans- and interdisciplinarity and community-participatory approaches than yet seen.

Effects of sea ice and wind speed on phytoplankton spring bloom in central and southern Baltic Sea

Pärn O, Lessin G, Stips A. Effects of sea ice and wind speed on phytoplankton spring bloom in central and southern Baltic Sea Anil AChandrashe. PLOS ONE [Internet]. 2021 ;16(3):e0242637. Available from: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0242637
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

In this study, the effects of sea ice and wind speed on the timing and composition of phytoplankton spring bloom in the central and southern Baltic Sea are investigated by a hydrodynamic–biogeochemical model and observational data. The modelling experiment compared the results of a reference run in the presence of sea ice with those of a run in the absence of sea ice, which confirmed that ecological conditions differed significantly for both the scenarios. It has been found that diatoms dominate the phytoplankton biomass in the absence of sea ice, whereas dinoflagellates dominate the biomass in the presence of thin sea ice. The study concludes that under moderate ice conditions (representing the last few decades), dinoflagellates dominate the spring bloom phytoplankton biomass in the Baltic Sea, whereas diatoms will be dominant in the future as a result of climate change i.e. in the absence of sea ice.

Climate Change Impacts on Atlantic Oceanic Island Tuna Fisheries

Townhill BL, Couce E, Bell J, Reeves S, Yates O. Climate Change Impacts on Atlantic Oceanic Island Tuna Fisheries. Frontiers in Marine Science [Internet]. 2021 ;8. Available from: https://www.frontiersin.org/articles/10.3389/fmars.2021.634280/full?utm_source=F-AAE&utm_medium=EMLF&utm_campaign=MRK_1571277_45_Marine_20210309_arts_A
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Climate change is already affecting the distributions of marine fish, and future change is expected to have a particularly large impact on small islands that are reliant on the sea for much of their income. This study aims to develop an understanding of how climate change may affect the distribution of commercially important tuna in the waters around the United Kingdom’s Overseas Territories in the South Atlantic. The future suitable habitat of southern bluefin, albacore, bigeye, yellowfin and skipjack tunas were modelled under two future climate change scenarios. Of all the tunas, the waters of Tristan da Cunha are the most suitable for southern bluefin, and overall, the environmental conditions will remain so in the future. Tristan da Cunha is not projected to become more suitable for any of the other tuna species in the future. For the other tuna species, Ascension Island and Saint Helena will become more suitable in the future, particularly so for skipjack tuna around Ascension Island, as the temperature and salinity conditions change in these areas. Large marine protected areas have been designated around the territories, with those in Ascension and Tristan da Cunha closed to tuna fishing. Although these areas are small relative to the whole Atlantic, these model projections could be useful in understanding whether this protection will benefit tuna populations into the future, particularly where there is high site fidelity.

Characterizing Marine Heatwaves in the Kerguelen Plateau Region

Su Z, Pilo GS, Corney S, Holbrook NJ, Mori M, Ziegler P. Characterizing Marine Heatwaves in the Kerguelen Plateau Region. Frontiers in Marine Science [Internet]. 2021 ;7. Available from: https://www.frontiersin.org/articles/10.3389/fmars.2020.531297/full?utm_source=F-AAE&utm_medium=EMLF&utm_campaign=MRK_1571277_45_Marine_20210309_arts_A
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Marine heatwaves (MHWs) are prolonged extreme oceanic warm water events. Globally, the frequency and intensity of MHWs have been increasing in recent years, and it is expected that this trend is reflected in the Kerguelen Plateau region. MHWs can negatively impact the structure of marine biodiversity, marine ecosystems, and commercial fisheries. Considering that the KP is a hot-spot for marine biodiversity, characterizing MHWs and their drivers for this region is important, but has not been performed. Here, we characterize MHWs in the KP region between January 1994 and December 2016 using a combination of remotely sensed observations and output from a publicly available model hindcast simulation. We describe a strong MHW event that starts during the 2011/2012 austral summer and persists through winter, dissipating in late 2012. During the winter months, the anomalous temperature signal deepens from the surface to a depth of at least 150 m. We show that downwelling-favorable winds occur in the region during these months. At the end of 2012, as the MHW dissipates, upwelling-favorable winds prevail. We also show that the ocean temperature on the KP is significantly correlated with key modes of climate variability. Over the KP, temperature at both the ocean surface and at a depth of 150 m correlates significantly with the Indian Ocean Dipole. To the south of the KP, temperature variations are significantly correlated with the El Niño Southern Oscillation, and to both the north and south of the KP, with the Southern Annular Mode. These results suggest there may be potential predictability in ocean temperatures, and their extremes, in the KP region. Strong MHWs, like the event in 2012, may be detrimental to the unique ecosystem of this region, including economically relevant species, such as the Patagonian Toothfish.

Bottom Trawling Threatens Future Climate Refugia of Rhodoliths Globally

Fragkopoulou E, Serrão EA, Horta PA, Koerich G, Assis J. Bottom Trawling Threatens Future Climate Refugia of Rhodoliths Globally. Frontiers in Marine Science [Internet]. 2021 ;7. Available from: https://www.frontiersin.org/articles/10.3389/fmars.2020.594537/full?utm_source=F-AAE&utm_medium=EMLF&utm_campaign=MRK_1571277_45_Marine_20210309_arts_A
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Climate driven range shifts are driving the redistribution of marine species and threatening the functioning and stability of marine ecosystems. For species that are the structural basis of marine ecosystems, such effects can be magnified into drastic loss of ecosystem functioning and resilience. Rhodoliths are unattached calcareous red algae that provide key complex three-dimensional habitats for highly diverse biological communities. These globally distributed biodiversity hotspots are increasingly threatened by ongoing environmental changes, mainly ocean acidification and warming, with wide negative impacts anticipated in the years to come. These are superimposed upon major local stressors caused by direct destructive impacts, such as bottom trawling, which act synergistically in the deterioration of the rhodolith ecosystem health and function. Anticipating the potential impacts of future environmental changes on the rhodolith biome may inform timely mitigation strategies integrating local effects of bottom trawling over vulnerable areas at global scales. This study aimed to identify future climate refugia, as regions where persistence is predicted under contrasting climate scenarios, and to analyze their trawling threat levels. This was approached by developing species distribution models with ecologically relevant environmental predictors, combined with the development of a global bottom trawling intensity index to identify heavily fished regions overlaying rhodoliths. Our results revealed the importance of light, thermal stress and pH driving the global distribution of rhodoliths. Future projections showed poleward expansions and contractions of suitable habitats at lower latitudes, structuring cryptic depth refugia, particularly evident under the more severe warming scenario RCP 8.5. Our results suggest that if management and conservation measures are not taken, bottom trawling may directly threaten the persistence of key rhodolith refugia. Since rhodoliths have slow growth rates, high sensitivity and ecological importance, understanding how their current and future distribution might be susceptible to bottom trawling pressure, may contribute to determine the fate of both the species and their associated communities.

Modeling the impact of climate change on mussel aquaculture in a coastal upwelling system: A critical assessment

Fuentes-Santos I, Labarta U, Fernández-Reiriz MJosé, Kay S, Hjøllo SSætre, X. Alvarez-Salgado A. Modeling the impact of climate change on mussel aquaculture in a coastal upwelling system: A critical assessment. Science of The Total Environment [Internet]. 2021 ;775:145020. Available from: https://www.sciencedirect.com/science/article/pii/S0048969721000863?dgcid=raven_sd_search_email
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Forecasting of climate change impacts on marine aquaculture production has become a major research task, which requires taking into account the biases and uncertainties arising from ocean climate models in coastal areas, as well as considering culture management strategies. Focusing on the suspended mussel culture in the NW Iberian coastal upwelling system, we simulated current and future mussel growth by means of a multistructural net production Dynamic Energy Budget (DEB) model. We considered two scenarios and three ocean climate models to account for climate uncertainty, and applied a bias correction to the climate models in coastal areas. Our results show that the predicted impact of climate change on mussel growth is low compared with the role of the seeding time. However, the response of mussels varied across climate models, ranging from a minor growth decline to a moderate growth increase. Therefore, this work confirms that an accurate forecasting of climate change impacts on shellfish aquaculture should take into account the variability linked to both management strategies and climate uncertainty.

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