New Fossil Fish Discoveries and "Deep Time" Climate Change in the Canadian Arctic

December 5, 2017

By Michael D. Gottfried, Michigan State University

Despite the escalating impacts of climate change, today’s Canadian Arctic is still an "Icehouse" world marked by polar conditions. During the immensely long span of Earth’s existence, however, this has not always been the case. The fossil record and other sources of data for studying ancient climates show that the Arctic was far more temperate 50 million years ago during the early Eocene Epoch in Earth’s geologic history, an interval that marked the time of maximum global warmth after the extinction of the dinosaurs 65 million years ago. This "Greenhouse" interval is referred to by researchers as the Early Eocene Climate Optimum (EECO). The dramatically different Arctic of the EECO is demonstrated by the presence of crocodilians, lizards, early primates, hippo-like mammals, tapirs, and lush temperate rainforests at the same Arctic latitudes where polar bears live today. Summers were mild and wet, with temperatures reaching ~25°C, and winters very likely remained at or above freezing during the EECO at high Arctic sites approaching 80°N.

In our new study in Arctic Science, my co-author Jaelyn Eberle (University of Colorado) and I report on the latest fossil data from the still-unfolding story of the Arctic Eocene Greenhouse. Our study is based on recent discoveries from field research on northern Banks Island, on the western edge of the Canadian Arctic northeast of Inuvik (Northwest Territories). Banks Island preserves a marine-influenced record of Eocene life, which complements the better-known fossils from Ellesmere Island on the eastern side of the Canadian Arctic where a rich diversity of Eocene animals and plants reflect more terrestrial conditions. 

The Canadian Arctic islands. Inset: Eocene fossil sites on Banks Island are along the Eames River in Aulavik National Park (Gottfried and Eberle 2017)

Our report focuses on expanding the record of fossil fishes from Banks Island. Surprisingly, we discovered approximately 100 slender sharply pointed teeth that belong to the extinct genus Eutrichiurides, a relative of the mackerels. Eutrichiurides is otherwise known from a variety of significantly lower latitude sites in the United States, Europe, Africa, and India, indicating that these fish were capable of dispersing widely and much further north than previously recognized.

 
Teeth of Eutrichiurides from the Eocene of Banks Island. Scale bar = 5 mm. Inset shows a close-up of the characteristic expanded tip on these teeth (Gottfried and Eberle 2017)

We also described fossil scales of the bowfin Amia, a relatively primitive fish that is widely distributed today in North American freshwater environments but does not reach the Arctic. Particularly striking is that one of the distinctive scales is very large and suggests that the Eocene Arctic Amia reached a length of close to 1.5 m, nearly half a meter larger than the maximum size of living bowfins. We assume that like their living relatives both Eutrichiurides and Amia were active predators in the Canadian Arctic Eocene ocean, chasing down their prey in a nearly landlocked sea that was far less salty than today’s Arctic Ocean. They shared this environment with large numbers of sand-tiger sharks along with stingrays, other bony fishes including pikes and gars, and crocodilians as was reported in an earlier paper.

 
Large lateral line scale of Eocene Amia from Banks Island, anterior to the right. Scale bar = 1 cm 
(Gottfried and Eberle 2017)

The 50 million-year-old fossil record from the Canadian Arctic during an interval of very mild conditions is of broader interest because it can potentially help us predict the future impacts of climate change in high-latitude environments. If efforts to slow the pace and reduce the impact of climate change on the Arctic ecosystem are not successful, the polar environment of the future may end up more closely resembling the temperate Eocene Greenhouse than the Icehouse conditions we see there today. It is thought provoking that these potentially very dramatic changes are happening within a human historical timescale, as opposed to "deep time" environmental changes that have occurred on a geological timescale spanning millions of years of Earth’s history.

Field research on Banks Island 

Reaching the fossil sites on Banks Island involved flying via helicopter from Sachs Harbour, the small community at the southern end of Banks Island reachable by air from Inuvik, to our campsite near the Eames River in Aulavik National Park at the northern end of the island. Our field area in Aulavik (the least-visited national park in Canada) is home to a very large population of muskox, who were frequently around our camp, and a small pack of curious but nonthreatening Arctic wolves—far more bothersome than the wolves were the millions of voracious mosquitoes!

Our June 2012 campsite in Aulavik National Park with our Canadian Helicopters transport leaving after we set up camp (Michael Gottfried)

Collecting the fossils meant hiking for several kilometers from our camp each day to one or more fossil sites and crawling along the very loosely consolidated Eocene-age sandy layers of sediment looking for teeth, scales, and bones that had weathered out and were laying on the surface. We also used fine mesh screens to sieve for very small specimens. The terrain on northern Banks Island is primarily lowland tundra cut through by river valleys, with patches of dwarf willow, sedges and grasses, and low boggy areas and small lakes. The summer 2012 expedition that I participated in took place right over the solstice, so we had 24 hours of full daylightan interesting experience, but to be honest not always welcome when you have (as I did) a light yellow tent, which at times felt like being inside a light bulb. Any inconvenience, however, either from mosquitoes or the Midnight Sun, was easy to tolerate given how privileged we were to be doing field research in the unique and beautiful environment on Banks Island.

Acknowledgments 

The 2012 Banks Island Eocene team was led by Jaelyn Eberle and also included J. Howard Hutchison (now retired from the University of California-Berkeley) and Brian Schubert, a paleobotanist based at the University of Louisiana-Lafayette. Thanks go to all those who have participated in Canadian Arctic field expeditions, the Canadian Museum of Nature where the specimens are curated and housed, the community of Sachs Harbour for their friendly welcome, and for logistical support the Parks Canada Western Field Unit, Polar Continental Shelf Program (Natural Resources Canada), Aurora Institute, and Canadian Helicopters. The primary source of funding for this research was through a grant to Jaelyn Eberle from the U.S. National Science Foundation, and I would also like to thank Michigan State University for supporting my participation in this research.
 
Eocene fossil locality in Aulavik National Park on Banks Island—specimens were collected on the surface of the dark reddish-colored loosely consolidated sandy horizons (Michael Gottfried)


 

Dr. Michael D. Gottfried
 is in the Department of Earth and Environmental Sciences at Michigan State University and Curator of Vertebrate Paleontology at the MSU Museum. He has conducted field-based research on fossil vertebrates from the Arctic, Antarctica, New Zealand, Madagascar, East Africa, and the United States. His research on the evolutionary history of Great White Sharks led to involvement both on- and off-camera in several documentary films for the National Geographic Channel, Discovery Channel, and Australian and German television. He teaches paleontology, glacial geology and climate change, and large non-majors science classes; has organized and led student study abroad programs to Antarctica and Iceland; and also serves as a lecturer and guide on ship-based expeditions to Antarctica, the Arctic, and the Russian Far East.

Filed Under: Science News Arctic Science

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