Dynamics of primary productivity in the northeastern Bay of Bengal over the last 26 000 years

At present, variations of primary productivity (PP) in the Bay of Bengal (BoB) are driven by salinity-related stratification, which is controlled by the Indian summer monsoon (ISM). The relationships between PP, precipitation, and more generally climate in the past are not clearly understood. Here, we present a new record of PP based on the examination of coccolithophore assemblages in a 26 000-year sedimentary series retrieved in the northeastern BoB (core MD77-176). We compare our PP records to published climate and monsoon records, as well as outputs from numerical experiments obtained with the Earth system model IPSL-CM5A-LR, including the marine biogeochemical component PISCES, and with the transient climate simulation TraCE-21. Our results show that PP was most probably controlled by nutrient contents and distribution within the upper water column, which were predominantly influenced by (i) regional river systems between 26 and 19 ka, i.e. when sea level was relatively low and climate was relatively dry, and (ii) salinity-related stratification over the last 19 kyr, i.e. when sea level rose and more humid conditions prevailed. During that period, salinity and stratification were directly related to monsoon precipitation dynamics, which were chiefly forced by both insolation and Atlantic meridional overturning circulation (AMOC) strength. During Heinrich Stadial 1 and the Younger Dryas, i.e. when the AMOC collapsed, weaker South Asian precipitation diminished stratification and enhanced PP. During Bølling–Allerød, i.e. when the AMOC recovered, stronger South Asian precipitation increased stratification and subdued PP. Similarly, the precipitation peak recorded around the middle–early Holocene is consistent with a stronger stratification that drives PP minima.

Incorporating a monetary variable into the Schelling model addresses the issue of a decreasing entropy trace

The Schelling model of segregation has been shown to have a simulation trace which decreases the entropy of its states as the aggregate number of residential agents surrounded by a threshold of equally labeled agents increases. This introduces a paradox which goes against the second law of thermodynamics that states how entropy must increase. In the efforts to bring principles of physics into the modeling of sociological phenomena this must be addressed. A modification of the model is introduced where a monetary variable is provided to the residential agents (sampled from reported income data), and a dynamic which acts upon this variable when an agent changes its location on the grid. The entropy of the simulation over the iterations is estimated in terms of the aggregate residential homogeneity and the aggregate income homogeneity. The dynamic on the monetary variable shows that it can increase the entropy of the states over the simulation. The path of the traces with both variables in the results show that the shape of the region of entropy is followed supporting that the decrease of entropy due to the residential clustering has a parallel and independent effect increasing the entropy via the monetary variable.

Dynamics of primary productivity in the northeastern Bay of Bengal over the last 26 000 years

At present, variations of primary productivity (PP) in the Bay of Bengal (BoB) are responding to salinity-related-stratification which is controlled by the Indian Summer Monsoon (ISM). The relationships between PP, ISM, and to a broader scale, North Atlantic climate rapid variability in the past, are not clearly understood. Here, we present a new record of PP based on the examination of coccolithophore assemblages in a 26 000 years sedimentary record, retrieved in the northeastern BoB (core MD77-176). Comparisons with published climate and monsoon records, as well as outputs from the transient climate simulation TraCE-21 and experiments run with the Earth System Model IPSL-CM5A-LR, including marine biogeochemical components, helped us interpret our PP records in the context of ISM and Atlantic Overturning Meridional Circulation (AMOC) changes. We demonstrate that PP is influenced by vertical stratification in the upper water column over the last 26 000 years (26 kyr BP). It is controlled by wind-driven mixing from 26 to 19 kyr BP, i.e., when dry climate conditions and reduced freshwater inputs occurred, and by salinity-related-stratification over the last 19 kyr BP (since the Last Glacial Maximum), i.e., when humid conditions prevailed. During the deglaciation, salinity and stratification are related to monsoon precipitation dynamics, which are chiefly forced by both, insolation and the strength of the AMOC. The collapse (recovery) of the AMOC during Heinrich Stadial 1 (Bølling Allerød) weakened (strengthened) ISM and diminished (increased) stratification, thus enhancing (subduing) productivity.

Training a Multilingual Sportscaster: Using Perceptual Context to Learn Language

We present a novel framework for learning to interpret and generate language using only perceptual context as supervision. We demonstrate its capabilities by developing a system that learns to sportscast simulated robot soccer games in both English and Korean without any language-specific prior knowledge. Training employs only ambiguous supervision consisting of a stream of descriptive textual comments and a sequence of events extracted from the simulation trace. The system simultaneously establishes correspondences between individual comments and the events that they describe while building a translation model that supports both parsing and generation. We also present a novel algorithm for learning which events are worth describing. Human evaluations of the generated commentaries indicate they are of reasonable quality and in some cases even on par with those produced by humans for our limited domain.