Sérgio H. Faria

Towards a continuous population model for natural language vowel shift.

The Great English Vowel Shift of 16th-19th centuries and the current Northern Cities Vowel Shift are two examples of collective language processes characterized by regular phonetic changes, that is, gradual changes in vowel pronunciation over time. Here we develop a structured population approach to modeling such regular changes in the vowel systems of natural languages, taking into account learning patterns and effects such as social trends. We treat vowel pronunciation as a continuous variable in vowel space and allow for a continuous dependence of vowel pronunciation in time and age of the speaker. The theory of mixtures with continuous diversity provides a framework for the model, which extends the McKendrick-von Foerster equation to populations with age and phonetic structures. We develop the general balance equations for such populations and propose explicit expressions for the factors that impact the evolution of the vowel pronunciation distribution. For illustration, we present two examples of numerical simulations. In the first one we study a stationary solution corresponding to a state of phonetic equilibrium, in which speakers of all ages share a similar phonetic profile. We characterize the variance of the phonetic distribution in terms of a parameter measuring a ratio of phonetic attraction to dispersion. In the second example we show how vowel shift occurs upon starting with an initial condition consisting of a majority pronunciation that is affected by an immigrant minority with a different vowel pronunciation distribution. The approach developed here for vowel systems may be applied also to other learning situations and other time-dependent processes of cognition in self-interacting populations, like opinions or perceptions.

Mitigation implications of an ice‐free summer in the Arctic Ocean

The rapid loss of sea ice in the Arctic is one of the most striking manifestations of climate change. As sea ice melts, more open water is exposed to solar radiation, absorbing heat and generating a sea-ice–albedo feedback that reinforces Arctic warming. Recent studies stress the significance of this feedback mechanism and suggest that ice-free summer conditions in the Arctic Ocean may occur faster than previously expected, even under low-emissions pathways. Here we use an integrated assessment model to explore the implications of a potentially rapid sea-ice-loss process. We consider a scenario leading to a full month free of sea ice in September 2050, followed by three potential trajectories afterward: partial recovery, stabilization, and continued loss of sea ice. We analyze how these scenarios affect the efforts to keep global temperature increase below 2°C. Our results show that sea-ice melting in the Arctic requires more stringent mitigation efforts globally. We find that global CO2 emissions would need to reach zero levels 5–15 years earlier and that the carbon budget would need to be reduced by 20%–51% to offset this additional source of warming. The extra mitigation effort would imply an 18%–59% higher mitigation cost to society. Our results also show that to achieve the 1.5°C target in the presence of ice-free summers negative emissions would be needed. This study highlights the need for a better understanding of how the rapid changes observed in the Arctic may impact our society.

The EDML Drilling Site

To become a polar explorer in the early 20th century was an exciting call for many, but vocation for just a few properly gifted. The occupation required not only intrepidity and exceptional physical condition, but also talent to convince potential sponsors of the predictability of unpredictable expeditions and nerves to withstand the perpetual fight against time.

Antarctica and EPICA

In German, an ice sheet of the type covering Antarctica is usually called an Eisschild or Eispanzer, which can loosely be translated as an “ice shield” or “ice armour”, respectively.

Multiscale Structure of the EDML Core

As explained in Sects. 2.1 and 2.3, whenever a snow layer is formed and buried by subsequent snow falls, a new portion of the ice-sheet stratigraphy and climate record begins to take shape.

EDML Line-Scan Images

As explained in Sect. 4.4, an ice-core line-scanner (LS) is a device for recording the visual stratigraphy of ice cores in high-resolution (≈ 0.1 mm/pixel) digital images. In the case of the EDML Deep Ice Core, the LS device scans polished ice slabs cut lengthwise from every full metre of the EDML core, according to the cutting plan shown in Fig. 4.10.