Land-Sea Linkages in the Arctic

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The Arctic is undergoing historically unprecedented changes in weather, sea ice, temperature and ecosystems.  These changes have led to greater coastal erosion, greater export of freshwater, and changes to marine and terrestrial ecosystems, habitats, and productivity, among other trends. Meanwhile, many believe the Arctic “amplifies” large climate changes during both warm periods and ice ages and Arctic sea-ice cover even affects weather in heavily populated mid-latitude regions.  The causes of Arctic amplification are poorly understood.  Because instrumental records extend back only a few decades and climate varies on annual, decadal and longer time scales, the causes of ongoing Arctic climate change remain unclear. Thus, there is a growing need to combine instrumental and geologic records to understand how the Arctic Ocean and adjacent land masses have been influenced by a range of natural and anthropogenic factors. We are investigating the history of the Arctic Ocean, adjacent seas and land areas during the last 500,000 years to understand past sea ice history during periods of climate warming and to determine impacts on ecosystems and species.

Our Research: We are investigating the history of the Arctic Ocean and adjacent seas and land areas during the last 500,000 years. During this time, climate varied from ice ages with large ice sheets (glacial periods) to warmer conditions (interglacial periods), with shorter-term fluctuations also occurring. Warm climate intervals such as the early Holocene (~5,000-11,500 years ago), the Last Interglacial Period (~ 125,000-130,000 years ago), and Marine Oxygen Isotope Stage 11 (~400,000 to 450,000 years ago) are of particular interest as they may be comparable to warmer conditions in the future.

Why this Research is ImportantClimate and sea ice models did not predict the recent decline in sea ice and do not adequately predict the future of Arctic Ocean sea ice cover. In addition, instrumental records of temperature, precipitation, and sea-ice extent and thickness are available only for approximately the past century and only since 1979 for sea-ice satellite data. This time period is too short to document the causes of observed trends in sea ice and other related Arctic features. Paleoclimate records in Arctic Ocean sediments improve the understanding and modeling of patterns and causes of Arctic climate change. They also shed light on possible future climate change and the impacts of Arctic sea ice on mid-latitude weather. This research informs decision makers on issues related to ecosystems, endangered species, energy policy, national security, and transportation.

Paleoclimate reconstructions from the Arctic already suggest that recent atmospheric warming has reversed the regional climatic trends of the last few millennia. During recent decades, Arctic temperatures have increased while annual and seasonal Arctic Ocean sea ice cover has decreased. This has led to greater coastal erosion, greater export of freshwater, and changes in marine ecosystems, habitats, and productivity among other trends. Of particular concern is the decrease in Arctic sea ice extent and thickness since 1979, especially during summer months, which has outpaced the rates predicted by climate models. Because instrumental records extend back only a few decades and large interannual and decadal variability exists, the causes of ongoing Arctic climate change remain unclear. In addition, atmospheric carbon dioxide concentrations are approaching levels not seen in 3 million years. Thus, there is a growing need to understand how the Arctic Ocean responds to climate change caused by both natural and anthropogenic factors.

Objective(s)Major goals are to understand past Arctic sea ice history during past periods of climate warming and to determine impacts on ecosystems and species.

MethodsUSGS researchers, collaborating with scientists in the United States, Sweden, Germany and elsewhere, are collecting evidence from sediment cores in the Arctic Ocean and adjacent seas and land masses. The cores are used to determine how Arctic systems were affected by changing climate in the past and to help predict future changes. Scientists use different proxy methods to reconstruct past patterns in Arctic sea ice, ocean temperature, and bottom and surface ocean circulation. Reconstruction of sea ice history over the last 500,000 years uses evidence from sediment cores and surface sediment samples. The samples are collected from Arctic continental shelves, abyssal plains, the Yermak Plateau, the Morris Jesup Rise, and the Alpha, Lomonosov, and Mendeleev Ridges (see map). Benthic organisms (which live on the ocean floor) are influenced by bottom water temperatures and patterns of ocean circulation. In addition to controlling which species are present, water temperatures also affect the chemistry of their shells. To reconstruct patterns of past water temperature and circulation, analyses of the ratio of Mg/Ca in ostracode shells are combined with analyses of species composition. Records of ocean and land temperature during the last 12,000 years (Holocene) are being studied in Alaska and the Beaufort-Chukchi Sea region and compared to recent ocean warming in that region. The focus is currently on sites in the Northwind Ridge and Chukchi Sea region north of Alaska to improve understanding of Arctic Ocean temperature and circulation during past warm intervals.

Researchers deploying gravity corer off boat in Chukchi Sea.

Deployment of a gravity corer aboard USCGC Healy during an expedition to the Chukchi Sea. 

(Credit: Laura Gemery, USGS. Public domain.)