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The Late Quaternary Northwest Pacific : Palaeoenvironmental Change and Development of Regional Marine Chronostratigraphy
The Northwest (NW) Pacific contains a significant, but poorly constrained and poorly understood ice-rafted debris (IRD) belt extending from the subarctic to the mid-latitudes. While these deposits point to substantial glacial ice in the Kamchatka-Koryak region during the last glacial period, the timing and dynamics of glacial change are not well constrained. This thesis updates the Late Quaternary marine core record with a high resolution and multi-faceted study of environmental change. The thesis begins with a review of the state of knowledge relating to Late Quaternary glacial and climatic change in the NW Pacific. I present a high resolution, ~175 kyr study of site ODP 1207A (37.79ºN, 162.75ºE), encompassing IRD, 14C dating, benthic δ18O, tephrochronology and planktic foraminifera counts. The southern limit of ice-rafting is revealed to be further south than previously thought. This discovery, in conjunction with a new high resolution age model reveals new information about the scale and timing of large magnitude ice-rafting events from NE Siberia. Ice-rafting does not show synchronicity with other major Northern Hemisphere ice sheets. A second IRD analysis is presented for DSDP 580 (41.37ºN, 153.59ºE) where icebergs are known to have reached. I present an updated age model for DSDP 580 derived from both pre-existing age tie points and new tephrochronological data. Together, these new IRD records reveal periods of widespread glacial collapse and possible synchronous collapse of NE Siberian glacial ice ~40 ka BP. Chapter 6 presents a comprehensive analysis of XRF core scanning data of Late Quaternary sections of nine North Pacific cores. This analysis extracts palaeoenvironmental signals from element intensities and log ratios, which identify episodes of palaeoproductivity change and terrigenous input. The palaeoproductivity indicators Ba and Ca are used to identify inter-core stratigraphic tie-points at multiple N Pacific sites, particularly around the last deglaciation. Chapter 7 presents the results and analysis of coupled climate-iceberg model experiments, which explores the most likely source points for icebergs into the N Pacific. The model experiments are important indicators of IRD provenance and provide a foundation for future geochemical provenance studies.
Dissertation
In the heart of the canyon
A rafting trip through the Grand Canyon changes the lives of everyone on board, including a jaded guide; a septuagenarian couple who know they will never make this trip again; and a teenager and her mother, who will face the most daunting journey of all.
Book
Boil line
\"In this high-interest novel for young readers, Nate investigates the death of a river-rafting guide.\"-- Provided by publisher.
Book
Centennial-scale variations in the carbon cycle enhanced by high obliquity
Centennial-scale increases of atmospheric carbon dioxide, known as carbon dioxide jumps, are identified during deglacial, glacial and interglacial periods and linked to the Northern Hemisphere abrupt climate variations. However, the limited number of identified carbon dioxide jumps prevents investigating the role of orbital background conditions on the different components of the global carbon cycle that may lead to such rapid atmospheric carbon dioxide releases. Here we present a high-resolution carbon dioxide record measured on an Antarctic ice core between 260,000 and 190,000 years ago, which reveals seven additional carbon dioxide Jumps. Eighteen of the 22 jumps identified over the past 500,000 years occurred under a context of high obliquity. Simulations performed with an Earth system model of intermediate complexity point towards both the Southern Ocean and the continental biosphere as the two main carbon sources during carbon dioxide jumps connected to Heinrich ice rafting events. Notably, the continental biosphere appears as the obliquity-dependent carbon dioxide source for these abrupt events. We demonstrate that the orbital-scale external forcing directly impacts past abrupt atmospheric carbon dioxide changes.
Centennial-scale releases of atmospheric CO
2
occurred during periods of high obliquity over the past 500,000, suggesting a link between external forcing and atmospheric CO
2
variations, according to a record from an Antarctic ice core.
Journal Article
Elmer and the whales
When Elmer the patchwork elephant and his cousin Wilbur decide to go whale-watching, as their grandfather Eldo did at their age, their journey becomes far more of an adventure than they anticipated.
Book
The raftsmen
\"A dramatic retelling of four adventurers who crossed the North Atlantic on a raft, featuring archival photography, film stills taken aboard the raft, news reports, contemporary interviews and original illustrations.\"-- Provided by publisher.
Book