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The MWP at the Tivoli North Bay of New York's Hudson Estuary
Sritairat, S., Peteet, D.M., Kenna, T.C., Sambrotto, R., Kurdyla, D. and Guilderson, T. 2012. A history of vegetation sediment and nutrient dynamics at Tivoli North Bay, Hudson Estuary, New York. Estuarine, Coastal and Shelf Science 102-103: 24-35.

The authors write that "the mid-Hudson region contains freshwater peatland archives that have not been investigated," and they therefore state that "there is a need to identify this base-line information to assess past anthropogenic activities and climatic patterns in relation to projected shifts in climate and vegetation in the Mid-Hudson Valley region," which they indicate is an important resource for over 10 million people.

What was done
Sritairat et al. explored, as they describe it, "how climate and human impacts have influenced plant ecology, invasive species expansion, habitat loss, carbon storage, and nutrient dynamics over the past millennium based on the multiproxy analysis of sediment cores using palynology, macrofossil, sedimentological, and geochemical analyses," while working with marsh sediment cores obtained at the National Estuarine Research Reserve at Tivoli Bays on the Hudson Estuary, New York, USA.

What was learned
The six scientists first identified a pre-European settlement period (AD 826-1310) that had a "high percentage of Carya, a warmth-loving species (Fowells, 1965)," which finding, as they describe it, "supports an increase in temperature." In addition, at a depth dated to AD 1087 72, they found a charcoal maximum, referring to it as "a feature that is also found in other Hudson river marsh cores at Piermont (Pederson et al., 2005) and Iona (Peteet et al., 2006)," which represents, in their words, "the warm, dry Medieval Warm Period (MWP)," which they further state is "likely a result of a regional Hudson Valley MWP recorded on a larger spatial scale in other parts of North America and the globe."

What it means
Acknowledging that "while there is a debate if the MWP is a global phenomenon as the warming is not synchronized at all sites around the globe," Sritairat et al. write that "many paleoclimatic records suggest widespread climatic anomalies, such as parts of Europe (Mangini et al., 2005), Tasmania (Cook et al., 1991), Asia (Yang et al., 2002), and Africa (Alin and Cohen, 2003) during the same time period." And so it is that the case for the existence of a global MWP continues to grow as demonstrated by our regular reporting of a new study that testifies of the MWP's occurrence at a new and different location.

Alin, S.R. and Cohen, A.S. 2003. Lake-level history of Lake Tanganyika, East Africa, for the past 2500 years based on ostracode-inferred water-depth reconstruction. Palaeogeography, Palaeoclimatology, Palaeoecology 199: 31-49.

Cook, E., Bird, T., Peterson, M., Barbetti, M., Buckley, B., D'Arrigo, R., Francey, R. and Tans, P. 1991. Climatic-change in Tasmania inferred from a 1089-year tree-ring chronology of Huon Pine. Science 253: 1266-1268.

Fowells, H.A. 1965. Silvics of Forest Trees of the United States. U.S. Department of Agriculture, Washington, DC, USA.

Mangini, A., Spotl, C. and Verdes, P. 2005. Reconstruction of temperature in the Central Alps during the past 2000 yr from a delta(18)O stalagmite record. Earth and Planetary Science Letters 235: 741-751.

Pederson, D.C., Peteet, D.M., Kurdyla, D. and Guilderson, T. 2005. Medieval warming, little ice age, and European impact on the environment during the last millennium in the lower Hudson valley, New York, USA. Quaternary Research 63: 238-249.

Peteet, D.M., Peteet, D., Pederson, D., Kurdyla, D. and Guilderson, T. 2006. Hudson River paleoecology from marshes. In: Hudson River Fishes and Their Environment. American Fisheries Society Monograph.

Yang, B., Braeuning, A., Johnson, K.R. and Shi, Y.F. 2002. General characteristics of temperature variation in China during the last two millennia. Geophysical Research Letters 29: 10.1029/2001GL104485.

Reviewed 3 October 2012