Pacific-2100: Extreme warm events of the past as a guide for Earth’s future

Science Center Objects

Projections for AD 2100 suggest warming of +1-4°C in the North Pacific Ocean, which will result in widespread transformations throughout the marine environment and western North America. Many of these changes are beyond the predictive capabilities of current climate models. To better address this future uncertainty, our team is developing a geological framework using past warm intervals as analogues for future conditions. This project focuses on reconstructing past North Pacific and western North America environmental and ecosystem conditions using micropaleontology and geochemistry methods that highlight key warm intervals of both the recent past (Medieval Climate Anomaly, Holocene Thermal Maximum, the abrupt Bølling-Allerød event), as well as warm intervals in deep-time (Pleistocene Last Interglacial and the Mid-Pliocene Warm Period). These data will 1) support local and regional efforts to anticipate patterns and impacts of future change and 2) provide a valuable resource for climate modeling community to improve regional climate projections.

Statement of Problem:

Model projections of Earth’s AD 2100 climate depict a warmer world, with increases in ocean temperatures, changes in continental hydrologic cycles, and altered marine and terrestrial ecosystems. Current observations of extreme heat in the Northeast Pacific Ocean (+1-4°C above baseline), as well as drought and widespread forest fires throughout western North America, underscore how devastating these climate impacts may be in the future. Although climate models can provide insight into future conditions they are somewhat limited, particularly in illuminating phenomena such as ocean hypoxia, lake eutrophication, harmful algal blooms (HAB), etc. The paleoclimate record can help fill this gap as a detailed account of environmental conditions during past extreme warm intervals (“hyperthermals”) that serve as analogues for projected AD 2100 conditions and better inform society of potential risk.

           

Why this Research is Important

Paleoclimatology has long been recognized by national and international research communities as a key tool in understanding and addressing societal climate impacts. Our research supports numerous research priorities and strategy documents including the Future Earth Strategic Research Agenda 2014, National Research Council Report Sea Change 2015-2025 Decadal Survey of Ocean Sciences, National Global Change Research Plan 2012-2021, USGS Circular 1309: Facing Tomorrow’s Challenges, and the 2019 USGS Land Change Science Mission Area Guidance. This project highlights the importance of employing micropaleontology methods to improve understanding of patterns and drivers of change and impacts on ecosystems. Our research also provides vital insights into past cycles of high-frequency climate forcing driven by Pacific variability (El Nino - Southern Oscillation and the Pacific Decadal Oscillation). Further, this research will contribute to a better understanding of the California Current System’s upwelling history during past hyperthermals and its interplay with continental North American hydroclimate.

 

Objective(s):

Our research group combines classical micropaleontology (diatoms, silicoflagellates, and foraminifera) with cutting-edge scanning technology and geochemical methods to reconstruct paleoclimate records from marine and terrestrial environments. These protocols allow us to study past changes in ecology and ecosystem function, as well as variations in environmental conditions. Considering hyperthermals of the Holocene, Pleistocene, and Pliocene as analogues for Pacific Ocean conditions in AD 2100, the over-arching research objectives for this project are to:

1.  Determine the patterns of Pacific Ocean sea surface temperature (SST) across time and space, and place within a global framework.

2.  Examine Pacific Ocean conditions that have resulted in altered marine ecosystems.

3.  Develop a network of paleoclimate sites from continental western North America to test Pacific Ocean-North America climate teleconnections.

 

Methods:

Our team will generate records of Pacific Ocean and western North America environmental conditions during past hyperthermals from marine and terrestrial systems using sedimentary and biological archives. These sample types offer time resolution spanning from seasons to millennia and beyond, thus encompassing several key periods of past enhanced warmth. Specific hyperthermal targets include the Medieval Climate Anomaly (MCA; AD 800-1200), early/middle Holocene Thermal Maximum (HTM; 6,000 - 10,000 years ago), the abrupt Bølling-Allerød deglacial event (B-A; 14,000 years ago), the Last Interglacial (LIG; ~125,000 years ago), and the mid-Pliocene Warm Period (MPWP; ~3 million years ago). Results from these hyperthermals will be compared to one another, as well as to modern instrument observations where conditions allow. These data will ultimately place both current and projected AD 2100 conditions in the context of past hyperthermals. The specific approach for each project objective follows:

Objective 1: Address related research questions through the set-up of an alkenone biomarker SST proxy lab in collaboration with the USGS Pacific Coastal and Marine Science Center. By combining these results with multi-proxy assessments of depositional environments and plankton paleoecology, as well as collaborations with climate modeling experts, our group team will fully explore the impact of Pacific Ocean SST changes during hyperthermals.

Objective 2: Apply our team’s expertise in marine sediment proxies to examine the record of hyperthermals in the North Pacific from a variety of settings, including the CCS upwelling that has profound impacts on both the US West Coast marine ecosystem and western North America climate. These studies will be extended into the high-latitude waters of the Gulf of Alaska and the Bering Sea with a specific application of diatom micropaleontology methods to examine the geological history of marine HABs.

Objective 3: Analyze lakes and other terrestrial climate records to examine far-field impacts driven by the Pacific through comparisons with marine records. A centerpiece of this effort will be investigations at the Hagerman Fossil Beds (HAFO), a poorly studied lacustrine deposit (Lake Idaho) rich in diatoms and macroscopic fossils that contains terrestrial evidence of the Middle Pliocene Warm Period (~3 Ma), which is the most recent hyperthermal with CO2 concentrations that approach current levels (>400 ppm).