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Continuous high-resolution marine sediment records that preserve environmental conditions during the late Holocene (the last 3000 years) are unusual in dynamic environments of the Arctic continental shelf. This study utilizes several proxies of ocean conditions in a unique sediment record, which provides valuable insight into late Holocene oceanographic changes on the Mackenzie Shelf, Beaufort Sea

map of ocean circulation in Chukchi and Beaufort Seas with geographic names
Schematic ocean current circulation of Chukchi and Beaufort Seas and geographic names. Sediments in this study formed a composite record from three core sites: HLY1302 MC29, GGC30 and JPC32 (69.97°N, 137.24°W, denoted by the (magenta circle) on the Mackenzie shelf in 60 m water depth. The green arrows denote the main pathway of Pacific-origin water exiting Chukchi Sea shelf and contributing to the Chukchi Slope Current to the west and Beaufort Shelfbreak Jet to the east. The blue arrow represents the Shelf Current in the vicinity of Mackenzie Canyon. The Beaufort Gyre (yellow arrow) situates in the Canada Basin. The bathymetry (in meters) is from The International Bathymetric Chart of the Arctic Ocean (IBCAO) v3 (Jakobsson et al. 2012). Figure 1. in Gemery et al., 2023, Micropaleontology v. 69, no. 3

The Arctic Ocean is experiencing increasing warming, freshwater influx, river discharge and declining sea ice. These recent changes impact biological systems and marine species.  Disentangling the effects of anthropogenic activities from natural climate variability using sediment records in the Arctic is important to understand and better prepare for future change.

Understanding the Arctic’s response to past climate changes prior to instrumental observations is difficult because of the limited spatial and temporal resolution of proxy records. A new study by USGS researchers and collaborators uses continuous and well-preserved records of benthic ostracode and foraminifera faunal assemblages, shell isotope geochemistry, and biogenic silica to create a multi-proxy record of paleoenvironmental change on the Mackenzie Continental Shelf in the Beaufort Sea during the last 2000 years.

The record suggests warmer ocean temperatures during the Medieval Climate Anomaly (~800-1200 CE), and variable, colder conditions between the years ~1250 to 1900. Proxies in the most recent sediments of the record (~1950-1990) document large changes in productivity (silica), microfossil (foraminifera and ostracode) faunal abundance, distribution, and δ18O that suggest rapid changes in water mass properties.

The combined proxies analyzed in this record offer a detailed temporal record of the last 2000 years, from the Beaufort Sea, a critical part of the changing Arctic Ocean. Without the reconstruction of past environmental changes and processes that control them, future alterations in components of the Earth system cannot be reliably predicted. Additionally, paleoenvironmental reconstructions that capture the present state offer a contemporary baseline that can be used to detect and monitor ongoing and future ocean change.


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