Since the early twentieth century, the amplitudes of tidal constituents in the Gulf of Maine and Bay of Fundy display clear secular trends that are among the largest anywhere observed for a regional body of water. The M2amplitude at Eastport, Maine, increased at a rate of 14.1 ± 1.2 cm per century until it temporarily dropped during 1980–1990, apparently in response to changes in the wider North Atlantic. Annual tidal analyses indicate M2reached an all‐time high amplitude last year (2018). Here we report new estimates of tides derived from nineteenth century water‐level measurements found in the U.S. National Archives. Results from Eastport, Portland, and Pulpit Harbor (tied to Bar Harbor) do
Declining tropical cyclone frequency under global warming
Abstract Assessing the role of anthropogenic warming from temporally inhomogeneous historical data in the presence of large natural variability is difficult and has caused conflicting conclusions on detection and attribution of tropical cyclone (TC) trends. Here, using a reconstructed long-term proxy of annual TC numbers together with high-resolution climate model experiments, we show robust declining trends in the annual number of TCs at global and regional scales during the twentieth century. The Twentieth Century Reanalysis (20CR) dataset is used for reconstruction because, compared with other reanalyses, it assimilates only sea-level pressure fields rather than utilize all available observations in the troposphere, making it less sensitive to temporal inhomogeneities in the observations. It can also capture TC signatures from the pre-satellite era reasonably well. The declining trends found are consistent with the twentieth century weakening of the Hadley and Walker circulations, which make conditions for TC formation less favourable.
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- Award ID(s):
- 2043142
- NSF-PAR ID:
- 10399136
- Date Published:
- Journal Name:
- Nature Climate Change
- Volume:
- 12
- Issue:
- 7
- ISSN:
- 1758-678X
- Page Range / eLocation ID:
- 655 to 661
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract not follow the twentieth century trends and indicate that the Gulf of Maine tide changes commenced sometime in the late nineteenth or early twentieth centuries, coincident with a transition to modern rates of sea‐level rise as observed at Boston and Portland. General agreement is that sea level rise alone is insufficient to cause the twentieth‐century tide changes. A role for ocean stratification is suggested by the long‐term warming of Gulf of Maine waters; archival water temperatures at Boston, Portland, and Eastport show increases of ∼2 °C since the 1880s. In addition, a changing seasonal dependence in M2amplitudes is reflected in a changing seasonal dependence in water temperatures. The observations suggest that models seeking to reproduce Gulf of Maine tides must consider both sea level rise and long‐term changes in stratification. -
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1038/s41558-022-01388-4
