Hurricanes And Nor’easters in the late Holecene – Evidence For Large Natural Variability

We have been alerted by Ken Haapala of the Science and Environmental Policy Project to an interestng paper on paleo-climate which documents a large natural variation in the occurrence of hurricanes and nor’easters along the coast of North Carolina.

It is

Mallinson, D.J., Smith, C.W., Mahan, S., Culver, S.J. and McDowell, K. 2011. Barrier island response to late Holocene climate events, North Carolina, USA. Quaternary Research 76: 46-57

The abstract reads [highlight added]

The Outer Banks barrier islands of North Carolina, USA, contain a geologic record of inlet activity that extends from ca. 2200 cal yr BP to the present, and can be used as a proxy for storm activity. Optically stimulated luminescence (OSL) dating (26 samples) of inlet-fill and flood tide delta deposits, recognized in cores and geophysical data, provides the basis for understanding the chronology of storm impacts and comparison to other paleoclimate proxy data. OSL ages of historical inlet fill compare favorably to historical documentation of inlet activity, providing confidence in the technique. Comparison suggests that the Medieval Warm Period (MWP) and Little Ice Age (LIA) were both characterized by elevated storm conditions as indicated by much greater inlet activity relative to today. Given present understanding of atmospheric circulation patterns and sea-surface temperatures during the MWP and LIA, we suggest that increased inlet activity during the MWP responded to intensified hurricane impacts, while elevated inlet activity during the LIA was in response to increased nor’easter activity. A general decrease in storminess at mid-latitudes in the North Atlantic over the last 300 yr has allowed the system to evolve into a more continuous barrier with few inlets.

The conclusion reads

This study demonstrates that OSL is a viable tool for dating subtidal to intertidal barrier island inlet and flood-tide delta facies, and can provide valuable insight into barrier evolution and coastal response to varying climate conditions. Ages of inlet facies along the North Carolina Outer Banks indicate a period of large-scale inlet activity concentrated between Rodanthe and Ocracoke during the MWP, which we attribute to hurricane impacts, and a later period of elevated inlet activity during the Little Ice Age, which we attribute to an increase in nor’easter activity.Closure of most of these inlets occurred over the last 300 yr, probably reflecting more stable climate conditions, fewer storm impacts (both hurricane and nor’easter), and a decrease in the average wind intensity and wave energy field in the mid-latitudes of the North Atlantic.

This study suggests that we have been in a period of reduced storminess along the coast of North Carolina than is typical of the longer time period. It also illustrates the difficulty of extracting a human caused climate change component to this large natural variability.

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