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Abstract. Paleoclimatic records provide valuable information about Holocene climate, revealing aspects of climate variability for a multitude of sites around the world. However, such data also possess limitations. Proxy networks are spatially uneven, seasonally biased, uncertain in time, and present a variety of challenges when used in concert to illustrate the complex variations of past climate. Paleoclimatic data assimilation provides one approach to reconstructing past climate that can account for the diversenature of proxy records while maintaining the physics-based covariancestructures simulated by climate models. Here, we use paleoclimate dataassimilation to create a spatially complete reconstruction of temperatureover the past 12 000 years using proxy data from the Temperature 12k database and output from transient climate model simulations. Following the last glacial period, the reconstruction shows Holocene temperatures warming to a peak near 6400 years ago followed by a slow cooling toward the present day, supporting a mid-Holocene which is at least as warm as the preindustrial. Sensitivity tests show that if proxies have an overlooked summer bias, some apparent mid-Holocene warmth could actually represent summer trends rather than annual mean trends. Regardless, the potential effects of proxy seasonal biases are insufficient to align the reconstructed global mean temperature with the warming trends seen in transient model simulations.
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Accounting for transient dynamics could improve the use of marine protected areas as a reference point for fisheries management
Biological reference points for fishery management depend on estimates of current stock status relative to unfished biomass (depletion). The ratio of fish density outside to inside a marine reserve, the density ratio, could serve as a proxy for depletion for data-poor management. However, transient dynamics associated with time lags in returning to the unfished state following reserve implementation make that proxy inaccurate on short time scales. We assessed density ratio management rules using an age-structured, spatially explicit model of four US west coast nearshore fishes following reserve implementation, with scenarios encompassing sampling error, recruitment variability, and uncertainty in natural mortality. In deterministic simulations, management incorporating time lags generally resulted in a higher mean and lower variability in biomass over 20 years, but lower mean yield compared to management that did not. However, when stochastic recruitment was included, differences among simulations due to stochasticity were much greater than any difference in performance between management strategies. Nonetheless, in certain cases, accounting for time lags could help avoid unwarranted increases in harvest effort after reserve implementation.
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- Award ID(s):
- 1904615
- PAR ID:
- 10468754
- Publisher / Repository:
- Canadian Journal of Fisheries and Aquatic Sciences
- Date Published:
- Journal Name:
- Canadian Journal of Fisheries and Aquatic Sciences
- Volume:
- 80
- Issue:
- 1
- ISSN:
- 0706-652X
- Page Range / eLocation ID:
- 85 to 104
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1139/cjfas-2022-0125
