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Creator Governance in Social Media Entertainment
This article addresses the platformization of cultural production by offering a creator-centric account of industrial and governance issues in social media entertainment (SME). SME is our term for the emerging industry of native online cultural producers together with the platforms, intermediaries, and fan communities operating interdependently, and disruptively, alongside legacy media industries and across global media cultures. The central concern of the article is that these creators are not recognized as stakeholders in current debates both academic and policy on platform governance. The relationship between the platform behemoths and individual creators may seem grossly disproportionate, but insights from network economics suggest a more supple account of power. The interests of creators are examined in the “top-down” context of the exercise of platform governance and efforts, by platforms and the state, to improve it. Those interests are also canvassed from the “bottom up”—how creators and creator advocacy are organizing and acting collectively to improve prospects for creators in this emerging industry.
Journal Article
Impact of Ekman Pumping on the Meridional Coherence of the AMOC
The effect of wind‐induced vertical velocity on the meridional coherence of Atlantic meridional overtuning circulation (AMOC) is examined using theory, observations, and a numerical model. Two cases are considered: (a) the AMOC computed in depth coordinates and (b) the AMOC computed in isopycnal coordinates. In depth space, the difference between the AMOC at different latitudes is largely explained by vertical transport across the 1000m$1000\\,\\mathrm{m}$depth surface induced by Ekman pumping. In density space, this difference is explained by Ekman‐driven heave of the neutral surface separating the upper and lower limbs. This adiabatic “sloshing” changes the relative volumes of the upper and lower AMOC limbs, obscuring the distribution and advection of the diapycnal transports which characterize the AMOC. Plain Language Summary The Atlantic meridional overturning circulation (AMOC) is classically viewed as a continuous “conveyor” transporting warm water northward in its upper limb and cold water southward in its lower limb. It is natural to assume, then, that fluctuations in the AMOC strength are synchronous across latitude. However, observations from the last decade have drawn this interpretation into question, as the subtropical and subpolar AMOC show no evidence of temporal coherence. Here, we demonstrate that much of this lack of coherence can be explained by vertical velocities induced by wind over the North Atlantic. Key Point Lack of meridional coherence in observed Atlantic meridional overtuning circulation can largely be explained by Ekman pumping
Journal Article
OVERTURNING IN THE SUBPOLAR NORTH ATLANTIC PROGRAM
For decades oceanographers have understood the Atlantic meridional overturning circulation (AMOC) to be primarily driven by changes in the production of deep-water formation in the subpolar and subarctic North Atlantic. Indeed, current Intergovernmental Panel on Climate Change (IPCC) projections of an AMOC slowdown in the twenty-first century based on climate models are attributed to the inhibition of deep convection in the North Atlantic. However, observational evidence for this linkage has been elusive: there has been no clear demonstration of AMOC variability in response to changes in deep-water formation. The motivation for understanding this linkage is compelling, since the overturning circulation has been shown to sequester heat and anthropogenic carbon in the deep ocean. Furthermore, AMOC variability is expected to impact this sequestration as well as have consequences for regional and global climates through its effect on the poleward transport of warm water. Motivated by the need for a mechanistic understanding of the AMOC, an international community has assembled an observing system, Overturning in the Subpolar North Atlantic Program (OSNAP), to provide a continuous record of the transbasin fluxes of heat, mass, and freshwater, and to link that record to convective activity and water mass transformation at high latitudes. OSNAP, in conjunction with the Rapid Climate Change–Meridional Overturning Circulation and Heatflux Array (RAPID–MOCHA) at 26°N and other observational elements, will provide a comprehensive measure of the three-dimensional AMOC and an understanding of what drives its variability. The OSNAP observing system was fully deployed in the summer of 2014, and the first OSNAP data products are expected in the fall of 2017.
Journal Article
Ocean circulation causes the largest freshening event for 120 years in eastern subpolar North Atlantic
The Atlantic Ocean overturning circulation is important to the climate system because it carries heat and carbon northward, and from the surface to the deep ocean. The high salinity of the subpolar North Atlantic is a prerequisite for overturning circulation, and strong freshening could herald a slowdown. We show that the eastern subpolar North Atlantic underwent extreme freshening during 2012 to 2016, with a magnitude never seen before in 120 years of measurements. The cause was unusual winter wind patterns driving major changes in ocean circulation, including slowing of the North Atlantic Current and diversion of Arctic freshwater from the western boundary into the eastern basins. We find that wind-driven routing of Arctic-origin freshwater intimately links conditions on the North West Atlantic shelf and slope region with the eastern subpolar basins. This reveals the importance of atmospheric forcing of intra-basin circulation in determining the salinity of the subpolar North Atlantic.
The Atlantic Ocean overturning circulation is important to the global climate system. Here the authors show that eastern subpolar North Atlantic underwent extreme freshening during 2012 to 2016, with a magnitude never seen before in 120 years of surface measurements.
Journal Article
Slowing of the Atlantic meridional overturning circulation at 25° N
Atlantic Ocean trends
The circulation across the 25° N latitude line in the Atlantic Ocean between Africa and the Bahamas has become the benchmark for estimating the Atlantic meridional overturning circulation, an important component of global ocean transport that carries warm upper waters into far northern latitudes via the Gulf Stream and returns cold deep waters south across the Equator. Its heat transport contributes to the moderate climate of maritime and continental Europe. A new hydrographic section across 25° N was taken in 2004, and comparison with measurements from 1957, 1981, 1992 and 1998 reveals a slowing of almost a third between 1957 and 2004. This means that more Gulf Stream waters are now recirculating southwards at mid-ocean depths, and that southward transport of cold lower North Atlantic Deep Water has halved. Some climate models suggest that the anthropogenic increase in atmospheric CO
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will result in a slowdown of the Atlantic overturning circulation, so this latest finding will add fuel to the debate on climate change.
The Atlantic meridional overturning circulation carries warm upper waters into far-northern latitudes and returns cold deep waters southward across the Equator
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. Its heat transport makes a substantial contribution to the moderate climate of maritime and continental Europe, and any slowdown in the overturning circulation would have profound implications for climate change. A transatlantic section along latitude 25° N has been used as a baseline for estimating the overturning circulation and associated heat transport
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. Here we analyse a new 25° N transatlantic section and compare it with four previous sections taken over the past five decades. The comparison suggests that the Atlantic meridional overturning circulation has slowed by about 30 per cent between 1957 and 2004. Whereas the northward transport in the Gulf Stream across 25° N has remained nearly constant, the slowing is evident both in a 50 per cent larger southward-moving mid-ocean recirculation of thermocline waters, and also in a 50 per cent decrease in the southward transport of lower North Atlantic Deep Water between 3,000 and 5,000 m in depth. In 2004, more of the northward Gulf Stream flow was recirculating back southward in the thermocline within the subtropical gyre, and less was returning southward at depth.
Journal Article
Larval behaviour, dispersal and population connectivity in the deep sea
Ecosystem connectivity is an essential consideration for marine spatial planning of competing interests in the deep sea. Immobile, adult communities are connected through freely floating larvae, depending on new recruits for their health and to adapt to external pressures. We hypothesize that the vertical swimming ability of deep-sea larvae, before they permanently settle at the bottom, is one way larvae can control dispersal. We test this hypothesis with more than
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simulated particles with a range of active swimming behaviours embedded within the currents of a high-resolution ocean model. Despite much stronger horizontal ocean currents, vertical swimming of simulated larvae can have an order of magnitude impact on dispersal. These strong relationships between larval dispersal, pathways, and active swimming demonstrate that lack of data on larval behaviour traits is a serious impediment to modelling deep-sea ecosystem connectivity; this uncertainty greatly limits our ability to develop ecologically coherent marine protected area networks.
Journal Article
Characterizing the Interannual Variability of North Atlantic Subpolar Overturning
Variability of the Atlantic Meridional Overturning Circulation (MOC) has drawn extensive attention due to its impact on the global redistribution of heat and freshwater. Here we present the latest time series (2014–2022) of the Overturning in the Subpolar North Atlantic Program and characterize MOC interannual variability. We find that any single boundary current captures ∼30% of subpolar MOC interannual variability. However, to fully resolve MOC variability, a wide swath across the eastern subpolar basin is needed; in the Labrador Sea both boundaries are needed. Through a volume budget analysis for the subpolar basins' lower limbs, we estimate the magnitude of unresolved processes (e.g., diapycnal mixing) required to close the mean budget (∼2 Sv). We find that in the eastern subpolar basin surface‐forced transformation variability is linked to lower limb volume variability, which translates to MOC changes within the same year. In contrast, this linkage is weak in the Labrador Sea.
Journal Article
Atlantic Meridional Overturning Circulation: Observed Transport and Variability
The Atlantic Meridional Overturning Circulation (AMOC) extends from the Southern Ocean to the northern North Atlantic, transporting heat northwards throughout the South and North Atlantic, and sinking carbon and nutrients into the deep ocean. Climate models indicate that changes to the AMOC both herald and drive climate shifts. Intensive trans-basin AMOC observational systems have been put in place to continuously monitor meridional volume transport variability, and in some cases, heat, freshwater and carbon transport. These observational programs have been used to diagnose the magnitude and origins of transport variability, and to investigate impacts of variability on essential climate variables such as sea surface temperature, ocean heat content and coastal sea level. AMOC observing approaches vary between the different systems, ranging from trans-basin arrays (OSNAP, RAPID 26 N, 11 S, SAMBA 34.5 N) to arrays concentrating on western boundaries (e.g., RAPID WAVE, MOVE 16 N). In this paper, we outline the different approaches (aims, strengths and limitations) and summarize the key results to date. We also discuss alternate approaches for capturing AMOC variability including direct estimates (e.g., using sea level, bottom pressure, and hydrography from Lagrangian floats), indirect estimates applying budgetary approaches, state estimates or ocean reanalyses, and proxies. Based on the existing observations and their results, and the potential of new observational and formal synthesis approaches, we make suggestions as to how to evaluate a comprehensive, future-proof observational network of the AMOC to deepen our understanding of the AMOC and its role in global climate.
Journal Article
Temporal Variability of the Atlantic Meridional Overturning Circulation at 26.5°N
The vigor of Atlantic meridional overturning circulation (MOC) is thought to be vulnerable to global warming, but its short-term temporal variability is unknown so changes inferred from sparse observations on the decadal time scale of recent climate change are uncertain. We combine continuous measurements of the MOC (beginning in 2004) using the purposefully designed transatlantic Rapid Climate Change array of moored instruments deployed along 26.5°N, with time series of Gulf Stream transport and surface-layer Ekman transport to quantify its intra-annual variability. The year-long average overturning is 18.7 ± 5.6 sverdrups (Sv) (range: 4.0 to 34.9 Sv, where 1 Sv = a flow of ocean water of 10⁶ cubic meters per second). Interannual changes in the overturning can be monitored with a resolution of 1.5 Sv.
Journal Article