CAFA Publications

Author(s): McClenachan L, SB Scyphers, JH Grabowski

Project PI: Scyphers
DOI: https://doi.org/10.1007/s13280-019-01156-3

The ability of resource-dependent communities to adapt to climate change depends in part on their perceptions and prioritization of specific climate-related threats. In the Maine lobster fishery, which is highly vulnerable to warming water associated with climate change, we found a strong majority (84%) of fishers viewed warming water as a threat, but rank its impacts lower than other drivers of change (e.g., pollution). Two-thirds believed they will be personally affected by warming waters, but only half had plans to adapt. Those with adaptation plans demonstrated fundamentally different views of human agency in this system, observing greater anthropogenic threats, but also a greater ability to control the fishery through their own actions on the water and fisheries management processes. Lack of adaptation planning was linked to the view that warming waters result from natural cycles, and the expectation that technological advancements will help buffer the industry from warming waters.

Author(s): Nishikawa, H, EN Curchitser, J Fiechter, KA Rose, K Hedstrom

Project PI: Jacox
DOI: https://doi.org/10.1186/s40645-019-0257-2

The influence of the well-known 1976–1977 regime shift on the Northern anchovy (Engraulis mordax) and the Pacific sardine (Sardinops caeruleus) populations in the California Current System (CCS) is investigated using a climate-to-fishery model. This model consists of four coupled submodels (regional ocean circulation model; Eulerian nutrient-phytoplankton-zooplankton-detritus model; individual-based full life cycle anchovy and sardine model; agent-based fishery model). Analysis of a historical simulation (1958–1990) showed that survival fraction of age-0 anchovy was lower just after 1977, while survival fraction of age-0 sardine was relatively unaffected by the regime shift. The age-0 survival of both species was influenced by the growth in the larval stage. Simulated zooplankton densities in the historical simulation shifted from high to low in 1976–1977 in the CCS, with the shift being most drastic in winter in the coastal area. The model also shows that anchovy larvae feed extensively from winter to early spring in the coastal area, while sardine larvae were mainly distributed in the offshore area. The differential seasonal and spatial responses of zooplankton in the simulation caused anchovy survival to be more sensitive than sardine to the 1976–1977 regime shift. The model-generated zooplankton shift was a result of reduced phytoplankton production due to lowered nutrient concentrations after 1977 due to the weakening of both the coastal upwelling and mixed layer shoaling, which reduced the vertical nutrient flux from the bottom layer to the surface layer.

Author(s): Jacox, M.G., Alexander, M.A., Bograd, S.J. et al

Project PI: Jacox
DOI: https://doi.org/10.1038/s41586-020-2534-z

Marine heatwaves (MHWs)—discrete but prolonged periods of anomalously warm ocean temperatures—can drastically alter ocean ecosystems, with profound ecological and socioeconomic impacts1,2,3,4,5,6,7,8. Considerable effort has been directed at understanding the patterns, drivers and trends of MHWs globally9,10,11. Typically, MHWs are characterized on the basis of their intensity and persistence at a given location—an approach that is particularly relevant for corals and other sessile organisms that must endure increased temperatures. However, many ecologically and commercially important marine species respond to environmental disruptions by relocating to favourable habitats, and dramatic range shifts of mobile marine species are among the conspicuous impacts of MHWs1,4,12,13. Whereas spatial temperature shifts have been studied extensively in the context of long-term warming trends14,15,16,17,18, they are unaccounted for in existing global MHW analyses. Here we introduce thermal displacement as a metric that characterizes MHWs by the spatial shifts of surface temperature contours, instead of by local temperature anomalies, and use an observation-based global sea surface temperature dataset to calculate thermal displacements for all MHWs from 1982 to 2019. We show that thermal displacements during MHWs vary from tens to thousands of kilometres across the world’s oceans and do not correlate spatially with MHW intensity. Furthermore, short-term thermal displacements during MHWs are of comparable magnitude to century-scale shifts inferred from warming trends18, although their global spatial patterns are very different. These results expand our understanding of MHWs and their potential impacts on marine species, revealing which regions are most susceptible to thermal displacement, and how such shifts may change under projected ocean warming. The findings also highlight the need for marine resource management to account for MHW-driven spatial shifts, which are of comparable scale to those associated with long-term climate change and are already happening.

Author(s): Alexander, M. A., S. Shin, J. D. Scott, E. Curchitser, C. Stock

Project PI: Jacox
DOI: https://doi.org/10.1175/JCLI-D-19-0117.1

ROMS, a high-resolution regional ocean model, was used to study how climate change may affect the northwestern Atlantic Ocean. A control (CTRL) simulation was conducted for the recent past (1976–2005), and simulations with additional forcing at the surface and lateral boundaries, obtained from three different global climate models (GCMs) using the RCP8.5 scenario, were conducted to represent the future (2070–99). The climate change response was obtained from the difference between the CTRL and each of the three future simulations. All three ROMS simulations indicated large increases in sea surface temperatures (SSTs) over most of the domain except off the eastern U.S. seaboard resulting from weakening of the Gulf Stream. There are also substantial intermodel differences in the response, including a southward shift of the Gulf Stream in one simulation and a slight northward shift in the other two, with corresponding changes in eddy activity. The depth of maximum warming varied among the three simulations, resulting in differences in the bottom temperature response in coastal regions, including the Gulf of Maine and the West Florida Shelf. The surface salinity decreased in the northern part of the domain and increased in the south in all three experiments, although the freshening extended much farther south in one ROMS simulation relative to the other two, and also relative to the GCM that provided the large-scale forcing. Thus, while high resolution allows for a better representation of currents and bathymetry, the response to climate change can vary considerably depending on the large-scale forcing.

Author(s): Smith, J. A., Muhling, B., Sweeney, J., Tommasi, D., Pozo Buil, M., Fiechter, J., & Jacox, M. G.

Project PI: Jacox
DOI: https://doi.org/10.1111/fog.12529

Many fish species are shifting spatial distributions in response to climate change, but projecting these shifts and measuring their impact at fine scales are challenging. We present a simulation that projects change in fishery landings due to spatial distribution shifts, by combining regional ocean and biogeochemical models (forced by three earth system models, ESMs: GFDL-ESM2M, HadGEM2-ES, IPSL-CM5A-MR), correlative models for species distribution and port-level landings, and a simulation framework which provides realistic values for species abundance and fishery conditions using an historical “reference period”. We demonstrate this approach for the northern subpopulation of Pacific sardine, an iconic commercial species for the U.S. West Coast. We found a northward shift in sardine landings (based on the northern subpopulation's habitat suitability), with projected declines at southern ports (20%–50% decline by 2080) and an increase (up to 50%) or no change at northern ports, and this was consistent across the three ESMs. Total sardine landings were more uncertain, with HadGEM2 indicating a 20% decline from 2000 to 15 levels by 2070 (a rate of 170 mt/y), IPSL a 10% increase (115 mt/y), and GFDL an 15% increase by the year ~2050 followed by a sharp decrease. The ESMs also differed in their projected change to the timing of the fishing season and frequency of fishery closures. Our simulation also identified key constraints on future landings that can be targeted by more tactical assessment; these included the seasonality of quota allocation and the abundance of other species in the catch portfolio.

Author(s): Smith, JA, et al

Project PI: Jacox
DOI: https://doi.org/10.1111/fog.12529

Many fish species are shifting spatial distributions in response to climate change, but projecting these shifts and measuring their impact at fine scales are challenging. We present a simulation that projects change in fishery landings due to spatial distribution shifts, by combining regional ocean and biogeochemical models (forced by three earth system models, ESMs: GFDL-ESM2M, HadGEM2-ES, IPSL-CM5A-MR), correlative models for species distribution and port-level landings, and a simulation framework which provides realistic values for species abundance and fishery conditions using an historical “reference period”. We demonstrate this approach for the northern subpopulation of Pacific sardine, an iconic commercial species for the U.S. West Coast. We found a northward shift in sardine landings (based on the northern subpopulation's habitat suitability), with projected declines at southern ports (20%–50% decline by 2080) and an increase (up to 50%) or no change at northern ports, and this was consistent across the three ESMs. Total sardine landings were more uncertain, with HadGEM2 indicating a 20% decline from 2000 to 15 levels by 2070 (a rate of 170 mt/y), IPSL a 10% increase (115 mt/y), and GFDL an 15% increase by the year ~2050 followed by a sharp decrease. The ESMs also differed in their projected change to the timing of the fishing season and frequency of fishery closures. Our simulation also identified key constraints on future landings that can be targeted by more tactical assessment; these included the seasonality of quota allocation and the abundance of other species in the catch portfolio.

Author(s): Slesinger, E., Saba, G., Young, R., Andres, A., Saba, V., Phelan, B., Rosendale, J., Wieczorek, D., Seibel, B.

Project PI: Saba
DOI: https://doi.org/10.1371/journal.pone.0244002

Over the last decade, ocean temperature on the U.S. Northeast Continental Shelf (U.S. NES) has warmed faster than the global average and is associated with observed distribution changes of the northern stock of black sea bass (Centropristis striata). Mechanistic models based on physiological responses to environmental conditions can improve future habitat suitability projections. We measured maximum, standard metabolic rate, and hypoxia tolerance (Scrit) of the northern adult black sea bass stock to assess performance across the known temperature range of the species. Two methods, chase and swim-flume, were employed to obtain maximum metabolic rate to examine whether the methods varied, and if so, the impact on absolute aerobic scope. A subset of individuals was held at 30˚C for one month (30chronic˚C) prior to experiments to test acclimation potential. Absolute aerobic scope (maximum–standard metabolic rate) reached a maximum of 367.21 mgO2 kg-1 hr-1 at 24.4˚C while Scrit continued to increase in proportion to standard metabolic rate up to 30˚C. The 30chronic˚C group exhibited a significantly lower maximum metabolic rate and absolute aerobic scope in relation to the short-term acclimated group, but standard metabolic rate or Scrit were not affected. This suggests a decline in performance of oxygen demand processes (e.g. muscle contraction) beyond 24˚C despite maintenance of oxygen supply. The Metabolic Index, calculated from Scrit as an estimate of potential aerobic scope, closely matched the measured factorial aerobic scope (maximum / standard metabolic rate) and declined with increasing temperature to a minimum below 3. This may represent a critical threshold value for the species. With temperatures on the U.S. NES projected to increase above 24˚C in the next 80-years in the southern portion of the northern stock’s range, it is likely black sea bass range will continue to shift poleward as the ocean continues to warm.

Author(s): Zang, Z., Ji, R., Feng, Z., Chen, C., Li, S., Davis, C.S.

Project PI: Ji/David/Rubao
DOI: https://doi.org/10.1093/icesjms/fsab102

The signal of phytoplankton responses to climate-related forcing can be obscured by the heterogeneity of shelf seascapes, making them difficult to detect from fragmented observations. In this study, a physical–biological model was applied to the Northwest Atlantic Shelf to capture the seasonality of phytoplankton. The difference in phytoplankton seasonality between the Mid-Atlantic Bight (MAB) and the Gulf of Maine (GoM) is a result of the interplay between nutrients and temperature: In the MAB, relatively high temperature in the cold season and longer oligotrophic environment in the warm season contribute to an earlier winter bloom and a later fall bloom; in the GoM, low temperature and strong mixing limit phytoplankton growth from late fall to early spring, resulting in a later spring bloom and an earlier fall bloom. Although the temperature difference between the GoM and the MAB might decrease in the future, stratification and surface nutrient regimes in these two regions will remain different owing to distinct thermohaline structures and deep-water intrusion. The spatial heterogeneity of phytoplankton dynamics affects pelagic and benthic production through connections with zooplankton and benthic–pelagic coupling.

Author(s): McClenachan L, M Marra, N Record, J Grabowski, B Neal, SB Scyphers.

Project PI: Scyphers
DOI: https://doi.org/10.1111/faf.12400

Climate-driven warming has both social and ecological effects on marine fisheries. While recent changes due to anthropogenic global warming have been documented, similar basin-wide changes have occurred in the past due to natural temperature fluctuations. Here, we document the effects of rapidly changing water temperatures along the United States’ east coast using observations from fisheries newspapers during a warming phase (1945–1951) and subsequent cooling phase (1952–1960) of the Atlantic Multidecadal Oscillation, which we compared to similar recent observations of warming waters (1998–2017). Historical warming and cooling events affected the abundance of species targeted by fishing, the prevalence of novel and invasive species, and physical access to targeted species. Fishing communities viewed historical cooling waters twice as negatively as they did warming waters (72% vs. 35% of observations). Colder waters were associated with a decrease in fishing opportunity due to storminess, while warming waters were associated with the potential for new fisheries. In contrast, recent warming waters were viewed as strongly negative by fishing communities (72% of observations), associated with disease, reductions in abundances of target species, and shifts in distributions across jurisdictional lines. This increasing perception that warming negatively affects local fisheries may be due to an overall reduction of opportunity in fisheries over the past half century, an awareness of the relative severity of warming today, larger changes in American culture, or a combination of these factors. Negative perceptions of recent warming waters’ effects on fisheries suggest that fishing communities are currently finding the prospect of climate adaptation difficult.

Author(s): Kang, D., E.N. Curchitser and A. Rosati

Project PI: Curchister
DOI: https://doi.org/10.1175/JPO-D-15-0235.1

The seasonal variability of the mean kinetic energy (MKE) and eddy kinetic energy (EKE) of the Gulf Stream (GS) is examined using high-resolution regional ocean model simulations. A set of three numerical experiments with different surface wind and buoyancy forcing is analyzed to investigate the mechanisms governing the seasonal cycle of upper ocean energetics. In the GS along-coast region, MKE has a significant seasonal cycle that peaks in summer, while EKE has two comparable peaks in May and September near the surface; the May peak decays rapidly with depth. In the off-coast region, MKE has a weak seasonal cycle that peaks in summer, while EKE has a dominant peak in May and a secondary peak in September near the surface. The May peak also decays with depth leaving the September peak as the only seasonal signal below 100 m. An analysis of the three numerical experiments suggests that the seasonal variability in the local wind forcing significantly impacts the September peak of the along-coast EKE through a local-flow barotropic instability process. Alternatively, the seasonal buoyancy forcing primarily impacts the flow baroclinic instability and is consequently related to the May peak of the upper ocean EKE in both regions. The analysis results indicate that the seasonal cycle of the along-coast MKE is influenced by both local energy generation by wind and the advection of energy from upstream regions. Finally, the MKE cycle and the September peak of EKE in the off-coast region are mainly affected by advection of energy from remote regions, giving rise to correlations with the seasonal cycle of remote winds.