Paige Newby

700 yr sedimentary record of intense hurricane landfalls in southern New England

Five intense (category 3 or greater) hurricanes occurring in 1635, 1638, 1815, 1869, and 1938 have made landfall on the New England coast since European settlement. Historical records indicate that four of these hurricanes (1635, 1638, 1815, and 1938) and hurricane Carol, a strong category 2 storm in 1954, produced significant storm surges (>3 m) in southern Rhode Island. Storm surges of this magnitude can overtop barrier islands, removing sediments from the beach and nearshore environment and depositing overwash fans across back-barrier marshes, lakes, and lagoons. In a regime of rising sea level, accumulation of marsh, lake, or lagoon sediments on top of overwash deposits will preserve a record of overwash deposition. We examined the record of overwash deposition at Succotash salt marsh in East Matunuck, Rhode Island, and tested the correlation with historical records of intense storms. Aerial photographs taken after hurricanes in 1954 and 1938 show overwash fans deposited at the site. Analysis of 14 sediment cores from the back-barrier marsh confirmed the presence of these fans and revealed that 4 additional large-scale overwash fans were deposited within the marsh sediments. The four overwash fans deposited since the early seventeenth century at Succotash Marsh matches the historical record of significant hurricane-induced storm surge. These fans were most likely deposited by hurricanes in 1954, 1938, 1815, and either 1638 or 1635. Radiocarbon dating of two prehistoric overwash fans indicated that these were deposited between A.D. 1295– 1407 and 1404–1446 and probably represent intense hurricane strikes. In the past 700 yr, at least 7 intense hurricanes struck the southern Rhode Island coast and produced a storm surge that overtopped the barrier at Succotash Marsh.

EVIDENCE FOR THE CLOSE CLIMATIC CONTROL OF NEW ENGLAND VEGETATION HISTORY

Sediments from lakes in the northeastern United States (“New England”) document climatic changes over the past 15 000 years that may, in turn, explain the long- term history of regional forest development. A rise in New England temperatures ∼14 600 yr BP (calendar years before present) coincided with the initial increase in spruce (Picea spp.) populations after deglaciation. Later temperature fluctuations correlated with changes in spruce forest composition until 11 600 yr BP, when evidence for a shift to warm, dry conditions agrees with the replacement of spruce by pine (Pinus spp.) populations. Raised lake levels indicate increased moisture availability by 8200 yr BP when mesic hemlock (Tsuga canadensis) and beech (Fagus grandifolia) populations replaced the dry-tolerant pines. Cooler-than-modern temperatures, however, persisted until 6000 yr BP and appear to have limited the expansion of hickory (Carya spp.) populations. Similarly, moisture- dependent chestnut (Castanea dentata) populations did not inc...

Parallel climate and vegetation responses to the early Holocene collapse of the Laurentide Ice Sheet

Parallel changes in lake-level and pollen data show that the rapid decline of the Laurentide Ice Sheet (LIS) between 10,000 and 8000 cal yr BP triggered a step-like change in North American climates: from an ice-sheet-and-insolation-dominated climate to a climate primarily controlled by insolation. Maps of the lake-level data from across eastern North America show a reorganization of climate patterns that the pollen data independently match. Raised lake-levels and expanded populations of moist-tolerant southern pines (Pinus) document that summer monsoons intensified in the southeastern United States between 9000 and 8000 cal yr BP. Simultaneously, low lake-levels and an eastward expansion of the prairie illustrate an increase in mid-continental aridity. After the Hudson Bay ice dome collapsed around 8200 cal yr BP, lake-levels rose in New England, as populations of mesic plant taxa, such as beech (Fagus) and hemlock (Tsuga), replaced those of dry-tolerant northern pines (Pinus). Available moisture increased there after a related century-scale period of colder-than-previous conditions around 8200 cal yr BP, which is also recorded in the pollen data. The comparison between pollen and lake-level data confirms that vegetations dynamics reflect climatic patterns on the millennial-scale.

A Record of Late‐Quaternary Moisture‐Balance Change and Vegetation Response from the White Mountains, New Hampshire

Abstract Changes in regional moisture availability over time affect hydrologic systems, such as lakes, and ecological processes, such as plant growth and reproduction. Long-term changes in moisture balance may help to explain broadscale changes in forest composition during the Quaternary period. In this article, Holocene lake-level changes and fossil pollen from Echo Lake, New Hampshire, are documented and the relationship between moisture-balance fluctuations and vegetation change in northern New England over the past 12,000 years is examined. Ground-penetrating radar profiles and five sediment cores provide evidence for two periods of low water levels at ca. 11,000–8,000 cal yr BP and at ca. 5,000–2,000 cal yr BP, respectively. During the first interval of low water level, dry-tolerant white pine (Pinus strobus) became common in the surrounding watershed. By ca. 8,000 cal yr BP, when the water level rose, hemlock (Tsuga), beech (Fagus), and birch (Betula), which prefer high soil-moisture levels, had increased in abundance. The second period of low water levels coincided with a decline in hemlock populations that has been widely attributed to a pathogen outbreak. The correlation between lake-level and vegetation change suggests that moisture availability, in addition to temperature, helps to shape vegetation dynamics by directly affecting plant populations and by influencing plant-pathogen and other ecological interactions.

Centennial‐to‐millennial hydrologic trends and variability along the North Atlantic Coast, USA, during the Holocene

Geophysical and sedimentary records from five lakes in Massachusetts reveal regionally coherent hydrologic variability during the Holocene. All of the lakes have risen since ~9.0 ka, but multicentury droughts after 5.6 ka repeatedly lowered their water levels. Quantified water level histories from the three best-studied lakes share >70% of their reconstructed variance. Four prominent low-water phases at 4.9–4.6, 4.2–3.9, 2.9–2.1, and 1.3–1.2 ka were synchronous across coastal lakes, even after accounting for age uncertainties. The droughts also affected sites up to ~200 km inland, but water level changes at 5.6–4.9 ka appear out of phase between inland and coastal lakes. During the enhanced multicentury variability after ~5.6 ka, droughts coincided with cooling in Greenland and may indicate circulation changes across the North Atlantic region. Overall, the records demonstrate that current water levels are exceptionally high and confirm the sensitivity of water resources in the northeast U.S. to climate change.