Scott
James D.
Scott
James D.
No Thumbnail Available
Search Results
Now showing
1 - 4 of 4
-
ArticleProjecting ocean acidification impacts for the Gulf of Maine to 2050: new tools and expectations(University of California Press, 2021-05-13) Siedlecki, Samantha A. ; Salisbury, Joseph E. ; Gledhill, Dwight K. ; Bastidas, Carolina ; Meseck, Shannon L. ; McGarry, Kelly ; Hunt, Christopher W. ; Alexander, Michael A. ; Lavoie, Diane ; Wang, Zhaohui Aleck ; Scott, James D. ; Brady, Damian C. ; Mlsna, Ivy ; Azetsu-Scott, Kumiko ; Liberti, Catherine M. ; Melrose, D. Christopher ; White, Meredith M. ; Pershing, Andrew J. ; Vandemark, Douglas ; Townsend, David W. ; Chen, Changsheng ; Mook, Bill ; Morrison, J. RuairidhOcean acidification (OA) is increasing predictably in the global ocean as rising levels of atmospheric carbon dioxide lead to higher oceanic concentrations of inorganic carbon. The Gulf of Maine (GOM) is a seasonally varying region of confluence for many processes that further affect the carbonate system including freshwater influences and high productivity, particularly near the coast where local processes impart a strong influence. Two main regions within the GOM currently experience carbonate conditions that are suboptimal for many organisms—the nearshore and subsurface deep shelf. OA trends over the past 15 years have been masked in the GOM by recent warming and changes to the regional circulation that locally supply more Gulf Stream waters. The region is home to many commercially important shellfish that are vulnerable to OA conditions, as well as to the human populations whose dependence on shellfish species in the fishery has continued to increase over the past decade. Through a review of the sensitivity of the regional marine ecosystem inhabitants, we identified a critical threshold of 1.5 for the aragonite saturation state (Ωa). A combination of regional high-resolution simulations that include coastal processes were used to project OA conditions for the GOM into 2050. By 2050, the Ωa declines everywhere in the GOM with most pronounced impacts near the coast, in subsurface waters, and associated with freshening. Under the RCP 8.5 projected climate scenario, the entire GOM will experience conditions below the critical Ωa threshold of 1.5 for most of the year by 2050. Despite these declines, the projected warming in the GOM imparts a partial compensatory effect to Ωa by elevating saturation states considerably above what would result from acidification alone and preserving some important fisheries locations, including much of Georges Bank, above the critical threshold.
-
ArticleENSO and Pacific decadal variability in the Community Climate System Model Version 4(American Meteorological Society, 2012-04-15) Deser, Clara ; Phillips, Adam S. ; Tomas, Robert A. ; Okumura, Yuko M. ; Alexander, Michael A. ; Capotondi, Antonietta ; Scott, James D. ; Kwon, Young-Oh ; Ohba, MasamichiThis study presents an overview of the El Niño–Southern Oscillation (ENSO) phenomenon and Pacific decadal variability (PDV) simulated in a multicentury preindustrial control integration of the NCAR Community Climate System Model version 4 (CCSM4) at nominal 1° latitude–longitude resolution. Several aspects of ENSO are improved in CCSM4 compared to its predecessor CCSM3, including the lengthened period (3–6 yr), the larger range of amplitude and frequency of events, and the longer duration of La Niña compared to El Niño. However, the overall magnitude of ENSO in CCSM4 is overestimated by ~30%. The simulated ENSO exhibits characteristics consistent with the delayed/recharge oscillator paradigm, including correspondence between the lengthened period and increased latitudinal width of the anomalous equatorial zonal wind stress. Global seasonal atmospheric teleconnections with accompanying impacts on precipitation and temperature are generally well simulated, although the wintertime deepening of the Aleutian low erroneously persists into spring. The vertical structure of the upper-ocean temperature response to ENSO in the north and south Pacific displays a realistic seasonal evolution, with notable asymmetries between warm and cold events. The model shows evidence of atmospheric circulation precursors over the North Pacific associated with the “seasonal footprinting mechanism,” similar to observations. Simulated PDV exhibits a significant spectral peak around 15 yr, with generally realistic spatial pattern and magnitude. However, PDV linkages between the tropics and extratropics are weaker than observed.
-
ArticleENSO’s impact on the gap wind regions of the eastern tropical Pacific Ocean(American Meteorological Society, 2012-05-15) Alexander, Michael A. ; Seo, Hyodae ; Xie, Shang-Ping ; Scott, James D.The recently released NCEP Climate Forecast System Reanalysis (CFSR) is used to examine the response to ENSO in the northeast tropical Pacific Ocean (NETP) during 1979–2009. The normally cool Pacific sea surface temperatures (SSTs) associated with wind jets through the gaps in the Central American mountains at Tehuantepec, Papagayo, and Panama are substantially warmer (colder) than the surrounding ocean during El Niño (La Niña) events. Ocean dynamics generate the ENSO-related SST anomalies in the gap wind regions as the surface fluxes damp the SSTs anomalies, while the Ekman heat transport is generally in quadrature with the anomalies. The ENSO-driven warming is associated with large-scale deepening of the thermocline; with the cold thermocline water at greater depths during El Niño in the NETP, it is less likely to be vertically mixed to the surface, particularly in the gap wind regions where the thermocline is normally very close to the surface. The thermocline deepening is enhanced to the south of the Costa Rica Dome in the Papagayo region, which contributes to the local ENSO-driven SST anomalies. The NETP thermocline changes are due to coastal Kelvin waves that initiate westward-propagating Rossby waves, and possibly ocean eddies, rather than by local Ekman pumping. These findings were confirmed with regional ocean model experiments: only integrations that included interannually varying ocean boundary conditions were able to simulate the thermocline deepening and localized warming in the NETP during El Niño events; the simulation with variable surface fluxes, but boundary conditions that repeated the seasonal cycle, did not.
-
ArticleWidespread habitat loss and redistribution of marine top predators in a changing ocean(American Association for the Advancement of Science, 2023-08-09) Braun, Camrin D. ; Lezama-Ochoa, Nerea ; Farchadi, Nima ; Arostegui, Martin C. ; Alexander, Michael ; Allyn, Andrew ; Bograd, Steven J. ; Brodie, Stephanie ; Crear, Daniel P. ; Curtis, Tobey H. ; Hazen, Elliott L. ; Kerney, Alex ; Mills, Katherine E. ; Pugh, Dylan ; Scott, James D. ; Welch, Heather ; Young-Morse, Riley ; Lewison, Rebecca L.The Northwest Atlantic Ocean and Gulf of Mexico are among the fastest warming ocean regions, a trend that is expected to continue through this century with far-reaching implications for marine ecosystems. We examine the distribution of 12 highly migratory top predator species using predictive models and project expected habitat changes using downscaled climate models. Our models predict widespread losses of suitable habitat for most species, concurrent with substantial northward displacement of core habitats >500 km. These changes include up to >70% loss of suitable habitat area for some commercially and ecologically important species. We also identify predicted hot spots of multi-species habitat loss focused offshore of the U.S. Southeast and Mid-Atlantic coasts. For several species, the predicted changes are already underway, which are likely to have substantial impacts on the efficacy of static regulatory frameworks used to manage highly migratory species. The ongoing and projected effects of climate change highlight the urgent need to adaptively and proactively manage dynamic marine ecosystems.