Holocene environments of Bermuda

Analysis of sediments from lake and marsh basins on Bermuda for palynomorphs, charcoal and inorganic particles allows reconstruction of the paleoenvironmental history of vegetation, fire and dust storm frequency and evaluation of the interplay between oceanic and atmospheric influences. Proximity to the Gulf Stream and seasonal shifts of the Bermuda-Azores High are responsible for the present climate on Bermuda, characterized by decreased summer rainfall and increased atmospheric temperatures. Both North Atlantic Oscillation and El Niño-Southern Oscillation (ENSO) affect the rainfall patterns on Bermuda and enhance the interannual to interdecadal variability.; Analysis of seasonal atmospheric deposition of palynomorphs, charcoal and inorganic particles provides the background to interpret the paleoenvironmental record. Palynomorph deposition is higher in summer than winter, and related to this, seasonality of flowering and high rainfall. Palynomorphs are almost exclusively derived locally, with long-distance pollen (Picea, Pinus and Quercus) being rare. Deposition of inorganic particles is bi-seasonal. The higher deposition of large particles (>50 μm), occurs in winter, apparently related to dust influx from North America, whereas lower deposition of smaller particles (<10 μm) occurs in summer and might be related to African sources. Analysis of three years of dust deposition in one of the atmospheric traps shows a seasonality pattern resembling NAO variability.; Accumulation of organic sediments in Devonshire Marsh was able to keep up with sea level rise in the Holocene. Marsh sediments preserve a record of vegetation change for the last 4000 years B.P. Proportional changes between Myrica cerifera and Sabal bermudana indicate periods of relatively higher (Myrica) and lower (Sabal) water levels. These changes can be related to fluctuations in sea surface temperatures and possible changes in production of North Atlantic Deep Water reconstructed from paleoceanographic records from the Bermuda rise.; The record of fires reconstructed from the charcoal particles preserved in the organic sediments of Devonshire Marsh shows that all major fires are associated with colonization and are attributed to antropogenic influences. The largest fire in the marsh took place in 1616, with a second major fire in 1914. Other fire events occurred in the late 1940s–early 1950s, 1957, 1971 and 1996.; So far only large (size) noncarbonate mineral grains have been analyzed in sediment records from Bermuda. Mineralogic analysis of these particles in Lover's Lake and Warwick Pond sediments and comparison with bird stomach contents attribute the high amounts of these particles prior to 500 yBP to transport by avian vectors related to migration patterns.