Seasonality and stable isotopes in planktonic foraminifera off Cape Cod, Massachusetts

Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 20 (2005): PA4011, doi:10.1029/2005PA001150.Monthly samples of stratified plankton tows taken from the slope waters off Cape Cod nearly 25 years ago are used to describe the seasonal succession of planktonic foraminifera and their oxygen isotope ratios. The 15°C seasonal cycle of sea surface temperature (SST) accounts for a diverse mixture of tropical to subpolar species. Summer samples include various Globigerinoides and Neogloboquadrina dutertrei, whereas winter and early spring species include Globigerina bulloides and Neogloboquadrina pachyderma (dextral). Globorotalia inflata lives all year but at varying water depths. Compared with the fauna in 1960–1961 (described by R. Cifelli), our samples seem warmer. Because sea surface salinity varies little during the year, δ18O is mostly a function of SST. Throughout the year, there are always species present with δ18O close to the calculated isotopic equilibrium of carbonate with surface seawater. This raises the possibility that seasonality can be estimated directly from the range of δ18O in a sediment sample provided that the δ18O-salinity relationship is the same as today.Funding was provided by NSF grant OCE-0117149

The Reinvention of Vouchers for a Color-Blind Era:A Racial Orders Account

Historically, vouchers, which provide a sum of money to parents for private education, were tools of racist oppression; but in recent decades some advocates claim them as “the civil rights issue of our time.” This article brings an analytic-historical perspective rooted in racial orders to understand how education vouchers have been reincarnated and reinvented since the Jim Crow era. Combining original primary research with statistical analysis, we identify multiple concurrent and consecutive transformations in voucher politics in three arenas of racial policy alliance contestation: expansion of color-blind policy designs, growing legal and political support from a conservative alliance, and a smorgasbord of voucher rationales rooted in color-blind framing. This approach demonstrates that education vouchers have never been racially neutral but served key roles with respect to prevailing racial hierarchies and contests

Western Atlantic Intertropical Convergence Zone variability over the last full glacial cycle

Pptn. changes in the western tropical Atlantic over the past 180,000 years are reconstructed using the stable carbon and deuterium isotopic compns. of higher plant leaf waxes preserved in Cariaco Basin sediments. Results indicate that less (more) pptn. fell over northern South America during stadial (interstadial) periods relative to today. Moreover, this trend is highly modulated by precessionally driven oscillations in Nov. insolation, such that dry events concurrent with periods of increased solar heating were less arid than those occurring when that heating was diminished (and visa versa). Together, these findings suggest that the duration of the seasonal displacement of the Intertropical Convergence Zone (ITCZ) was modified in response to changes in both the high latitude North Atlantic (presumably due to variations in the rate of meridional overturning circulation) and tropical insolation during the last glacial cycle, thus establishing an important link between seasonality and abrupt climate change