Annual Review of Marine Science最新文献

Releases of anthropogenic radionuclides from European nuclear fuel reprocessing plants enter the surface circulation of the high-latitude North Atlantic and are transported northward into the Arctic Ocean and southward from the Nordic Seas into the deep North Atlantic, thereby providing tracers of water circulation, mixing, ventilation, and deep-water formation. Early tracer studies focused on ¹³⁷Cs, which revealed some of the first significant insights into the Arctic Ocean circulation, while more recent work has benefited from advances in accelerator mass spectrometry to enable the measurement of the conservative, long-lived radionuclide tracers ¹²⁹I and ²³⁶U. The latest studies of these tracers, supported by simulations using the North Atlantic-Arctic Ocean-Sea Ice Model (NAOSIM) and enhanced by the use of transit time distributions to more precisely accommodate mixing, have provided a rich inventory of transport data for circulation in the Arctic and North Atlantic Oceans that are of great importance to global thermohaline circulation and climate.

The world's eastern boundary upwelling systems (EBUSs) contribute disproportionately to global ocean productivity and provide critical ecosystem services to human society. The impact of climate change on EBUSs and the ecosystems they support is thus a subject of considerable interest. Here, we review hypotheses of climate-driven change in the physics, biogeochemistry, and ecology of EBUSs; describe observed changes over recent decades; and present projected changes over the twenty-first century. Similarities in historical and projected change among EBUSs include a trend toward upwelling intensification in poleward regions, mitigatedwarming in near-coastal regions where upwelling intensifies, and enhanced water-column stratification and a shoaling mixed layer. However, there remains significant uncertainty in how EBUSs will evolve with climate change, particularly in how the sometimes competing changes in upwelling intensity, source-water chemistry, and stratification will affect productivity and ecosystem structure. We summarize the commonalities and differences in historical and projected change in EBUSs and conclude with an assessment of key remaining uncertainties and questions. Future studies will need to address these questions to better understand, project, and adapt to climate-driven changes in EBUSs.

I am a child of Sputnik, the satellite launched by the Soviet Union in 1957. That event created opportunities for me to escape the horrors of apartheid by emigrating from South Africa to the United States. There, fortuitously, I was given excellent opportunities to explore how an interplay between the waves and currents influences climate variability, from interannual El Niño events to millennial ice ages. During my career, I also witnessed intriguing facets of the interactions between the profoundly different worlds of science and of human affairs. Up to 1957, El Niño was welcomed as a blessing, but by 1982 it had become a curse-not because it changed, but because our human activities are making us vulnerable to natural climate variability. We have learned to cope admirably with the occasional failures of the Indian monsoons; the resultant famines are not as calamitous as they once were. What guidance does that limited success provide for a response to global warming, a climate change we humans are inducing? This article briefly summarizes how my career as a geoscientist brought me to the conclusion that a strategy to promote responsible stewardship of planet Earth should be based on love rather than fear. We can only love what we know, so warnings of imminent gloom and doom should be complemented with efforts to make everyone aware of the wonders of our amazing planet-the only one in the universe known to be habitable.

The regular movements of waves and tides are obvious representations of the oceans' rhythmicity. But the rhythms of marine life span across ecological niches and timescales, including short (in the range of hours) and long (in the range of days and months) periods. These rhythms regulate the physiology and behavior of individuals, as well as their interactions with each other and with the environment. This review highlights examples of rhythmicity in marine animals and algae that represent important groups of marine life across different habitats. The examples cover ecologically highly relevant species and a growing number of laboratory model systems that are used to disentangle key mechanistic principles. The review introduces fundamental concepts of chronobiology, such as the distinction between rhythmic and endogenous oscillator-driven processes. It also addresses the relevance of studying diverse rhythms and oscillators, as well as their interconnection, for making better predictions of how species will respond to environmental perturbations, including climate change. As the review aims to address scientists from the diverse fields of marine biology, ecology, and molecular chronobiology, all of which have their own scientific terms, we provide definitions of key terms throughout the article.

The Deepwater Horizon oil spill in the Gulf of Mexico in 2010 was the largest in US history, covering more than 1,000 km of shorelines and causing losses that exceeded $50 billion. While oil transformation processes are understood at the laboratory scale, the extent of the Deepwater Horizon spill made it challenging to integrate these processes in the field. This review tracks the Deepwater Horizon oil during its journey from the Mississippi Canyon block 252 (MC252) wellhead, first discussing the formation of the oil and gas plume and the ensuing oil droplet size distribution, then focusing on the behavior of the oil on the water surface with and without waves. It then reports on massive drifter experiments in the Gulf of Mexico and the impact of the Mississippi River on the oil transport. Finally, it concludes by addressing the formation of oil-particle aggregates. Although physical processes lend themselves to numerical modeling, we attempted to elucidate them without using advanced modeling, as our goal is to enhance communication among scientists, engineers, and other entities interested in oil spills.

Understanding the nature of organic matter flux in the ocean remains a major goal of oceanography because it impacts some of the most important processes in the ocean. Sinking particles are important for carbon dioxide removal from the atmosphere and its movement to the deep ocean. They also feed life below the ocean's productive surface and sustain life in the deep sea, in addition to depositing organic matter on the seafloor. However, the magnitude of all of these processes is dependent on the transformation of sinking particles during their journey through the water column. This review focuses on the movement of organic matter from the surface ocean to the deep sea via the biological carbon pump and examines the processes that prevent this downward movement-namely, attenuation via microbial colonization and zooplankton feeding. It also discusses how the depth-specific interactions among microbes, zooplankton, and aggregates determine carbon export as well as nutrient recycling, which in turn impact ocean production and Earth's climate.

Ocean carbon dioxide removal (OCDR) is rapidly attracting interest, as climate change is putting ecosystems at risk and endangering human communities globally. Due to the centrality of the ocean in the global carbon cycle, augmenting the carbon sequestration capacity of the ocean could be a powerful mechanism for the removal of legacy excess emissions. However, OCDR requires careful assessment due to the unique biophysical characteristics of the ocean and its centrality in the Earth system and many social systems. Using a sociotechnical system lens, this review identifies the sets of considerations that need to be included within robust assessments for OCDR decision-making. Specifically, it lays out the state of technical assessments of OCDR approaches along with key financial concerns, social issues (including public perceptions), and the underlying ethical debates and concerns that would need to be addressed if OCDR were to be deployed as a carbon dioxide removal strategy.

The Arctic Ocean's Beaufort Gyre is a dominant feature of the Arctic system, a prominent indicator of climate change, and possibly a control factor for high-latitude climate. The state of knowledge of the wind-driven Beaufort Gyre is reviewed here, including its forcing, relationship to sea-ice cover, source waters, circulation, and energetics. Recent decades have seen pronounced change in all elements of the Beaufort Gyre system. Sea-ice losses have accompanied an intensification of the gyre circulation and increasing heat and freshwater content. Present understanding of these changes is evaluated, and time series of heat and freshwater content are updated to include the most recent observations.

Nitrogen is a major limiting element for biological productivity, and thus understanding past variations in nitrogen cycling is central to understanding past and future ocean biogeochemical cycling, global climate cycles, and biodiversity. Organic nitrogen encapsulated in fossil biominerals is generally protected from alteration, making it an important archive of the marine nitrogen cycle on seasonal to million-year timescales. The isotopic composition of fossil-bound nitrogen reflects variations in the large-scale nitrogen inventory, local sources and processing, and ecological and physiological traits of organisms. The ability to measure trace amounts of fossil-bound nitrogen has expanded with recent method developments. In this article, we review the foundations and ground truthing for three important fossil-bound proxy types: diatoms, foraminifera, and corals. We highlight their utility with examples of high-resolution evidence for anthropogenic inputs of nitrogen to the oceans, glacial-interglacial-scale assessments of nitrogen inventory change, and evidence for enhanced CO₂ drawdown in the high-latitude ocean. Future directions include expanded method development, characterization of ecological and physiological variation, and exploration of extended timescales to push reconstructions further back in Earth's history.

Exchange of material across the nearshore region, extending from the shoreline to a few kilometers offshore, determines the concentrations of pathogens and nutrients near the coast and the transport of larvae, whose cross-shore positions influence dispersal and recruitment. Here, we describe a framework for estimating the relative importance of cross-shore exchange mechanisms, including winds, Stokes drift, rip currents, internal waves, and diurnal heating and cooling. For each mechanism, we define an exchange velocity as a function of environmental conditions. The exchange velocity applies for organisms that keep a particular depth due to swimming or buoyancy. A related exchange diffusivity quantifies horizontal spreading of particles without enough vertical swimming speed or buoyancy to counteract turbulent velocities. This framework provides a way to determinewhich processes are important for cross-shore exchange for a particular study site, time period, and particle behavior.