RECONSTRUCTING PAST STORMINESS IN HALIFAX HARBOUR THROUGH GRAIN-SIZE ANALYSIS OF MARINE SEDIMENT CORES

Abstract

The Intergovernmental Panel on Climate Change (ICPP, Trenberth, 2007) predicts that extra tropical storm tracks will move pole-ward and have higher precipitation rates and larger wind speeds at the end of the 21st century. Because of this, understanding patterns of past storminess in the Atlantic Canadian region has become increasingly important in order to improve the accuracy of modeling and predicting storms in the area. In light of the very short modern instrumental record of storminess in Eastern Canada, ‘a long-term proxy based record of storminess, extending back into the Holocene would provide both a basis for the evaluation of trends in past storminess and a firmer foundation for future predictions’ (p. 1, Clarke & Rendell 2009) In this study, sediment cores from the Northwest Arm and Purcell’s Cove in Halifax Harbour, Nova Scotia were examined for changes in sortable silt (SS) downcore using disaggregated inorganic grain-size (DIGS) analysis. An age model was created using a previously published sedimentation rate estimate in conjunction with existing Mercury (Hg) from one of the cores. Evidence from past studies indicates that grain-size measurements, and specifically SS in marine cores can be used to indicate past storminess on storm-dominated shelves. The results from this study indicate increased storminess in Halifax Harbour during the Little Ice Age (LIA, 1400-1700 CE). Other periods of increased storminess were also visible in the sediment record at ~1835-1885 CE, ~510-910 CE and ~10 CE. Future work should include more dating to increase the accuracy of the age model as well as increased temporal resolution.