Thomas M Cronin

Thomas M Cronin
United States Geological Survey | USGS · Florence Bascom Geoscience Center

About

338
Publications
52,088
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11,341
Citations
Additional affiliations
January 2009 - June 2019
United States Geological Survey
Position
  • Senior Geologist

Publications

Publications (338)
Article
The Arctic Ocean has experienced orbital and millennial-scale climate oscillations over the last 500 kilo-annum (ka) involving massive changes in global sea level and components of the Arctic cryosphere, including sea-ice cover, land-based ice sheets and ice shelves. Although these climate events are only partially understood, micropaleontological...
Article
Poseidonamicus is one of the most intensively studied genera among marine fossil ostracods due to its common occurrence in the world deep oceans and its distinctive morphological features. Many studies using Poseidonamicus have contributed to our understanding in a wide range of research topics, from evolutionary developmental biology to paleoenvir...
Article
Full-text available
Salinity-driven density stratification of the upper Arctic Ocean isolates sea-ice cover and cold, nutrient-poor surface waters from underlying warmer, nutrient-rich waters. Recently, stratification has strengthened in the western Arctic but has weakened in the eastern Arctic; it is unknown if these trends will continue. Here we present foraminifera...
Article
Full-text available
The northern sector of the Greenland Ice Sheet is considered to be particularly susceptible to ice mass loss arising from increased glacier discharge in the coming decades. However, the past extent and dynamics of outlet glaciers in this region, and hence their vulnerability to climate change, are poorly documented. In the summer of 2019, the Swedi...
Article
We evaluate the potential utility of Mg/Ca in the ostracode genera Sarsicytheridea and Paracyprideis as a paleotemperature proxy for continental shelf and upper slope waters of the Arctic Ocean and adjacent seas. Using sediment core-top and surface sediment samples, shells of three species, S. bradii, S. punctillata, and P. pseudopunctillata, were...
Article
Full-text available
Ostracoda (bivalved Crustacea) comprise a significant part of the benthic meiofauna in the Pacific-Arctic region, including more than 50 species, many with identifiable ecological tolerances. These species hold potential as useful indicators of past and future ecosystem changes. In this study, we examined benthic ostracodes from nearly 300 surface...
Article
Full-text available
Stable oxygen isotope measurements on calcitic valves of benthic ostracodes (δ¹⁸Oost) from the northern Bering and Chukchi Seas were used to examine ecological and hydrographic processes governing ostracode and associated seawater δ¹⁸O values. Five cryophilic taxa were analyzed for δ¹⁸Oost values: Sarsicytheridea bradii; Paracyprideis pseudopunctil...
Article
Stable oxygen isotope measurements on calcitic valves of benthic ostracodes (δ¹⁸Oost) from the northern Bering and Chukchi Seas were used to examine ecological and hydrographic processes governing ostracode and associated seawater δ¹⁸O values. Five cryophilic taxa were analyzed for δ¹⁸Oost values: Sarsicytheridea bradii; Paracyprideis pseudopunctil...
Preprint
Full-text available
The northern sector of the Greenland ice sheet is considered to be particularly susceptible to ice mass loss arising from increased glacier discharge in the coming decades. However, the past extent and dynamics of outlet glaciers in this region, and hence their vulnerability to climate change, are poorly documented. In the summer of 2019, the Swedi...
Article
Full-text available
Two different biostratigraphic approaches are used to identify Marine Isotope Stage 11 (MIS 11) in Arctic Ocean sediments. On the Lomonosov Ridge, globally calibrated nannofossil bioevents constrain the age of sediments back to MIS 13 (Core LOMROG12-3PC). In the Amerasian Basin the unique occurrence of the planktonic foraminifer Turborotalita egeli...
Conference Paper
The U.S. Atlantic Coastal Plain (ACP) preserves a number of marine terraces associated with paleo-shoreline escarpments that record various Quaternary sea-level highstands. One of the most widely studied periods of the late Quaternary is Marine Isotope Stage (MIS) 5e (~125-115 ka), where the Greenland and Antarctic Ice Sheets likely experienced sig...
Article
Full-text available
The processes controlling advance and retreat of outlet glaciers in fjords draining the Greenland Ice Sheet remain poorly known, undermining assessments of their dynamics and associated sea-level rise in a warming climate. Mass loss of the Greenland Ice Sheet has increased six-fold over the last four decades, with discharge and melt from outlet gla...
Article
Full-text available
Aim: The latitudinal diversity gradient (LDG) is a consequence of evolutionary and ecological mechanisms acting over long history, and thus is best investigated with organisms that have rich fossil records. However, combined neontological-palaeontological investigations are mostly limited to large, shelled invertebrates, which keeps our mechanistic...
Article
Full-text available
Marine Isotope Stage 11 from ~424 to 374 ka experienced peak interglacial warmth and highest global sea level ~410–400 ka. MIS 11 has received extensive study on the causes of its long duration and warmer than Holocene climate, which is anomalous in the last half million years. However, a major geographic gap in MIS 11 proxy records exists in the A...
Article
We reconstructed the last 10,000 years of Holocene relative sea-level rise (RSLR) from sediment core records near Chesapeake Bay, eastern United States, including new marsh records from the Potomac and Rappahannock Rivers, Virginia. Results show mean RSLR rates of 2.6 mm yr ⁻¹ from 10 to 8 kilo-annum (ka) due to combined final ice-sheet melting dur...
Article
Full-text available
Turborotalita quinqueloba is a species of planktic foraminifera commonly found in the sub-polar North Atlantic along the pathway of Atlantic waters in the Nordic seas and sometimes even in the Arctic Ocean, although its occurrence there remains poorly understood. Existing data show that T. quinqueloba is scarce in Holocene sediments from the centra...
Article
Full-text available
The hazards posed by infrequent major floods to communities along the Susquehanna River and the ecological health of Chesapeake Bay remain largely unconstrained due to the short length of streamgage records. Here we develop a history of high-flow events on the Susquehanna River during the late Holocene from flood deposits contained in MD99-2209, a...
Article
Full-text available
Climate warming is expected to destabilize permafrost carbon (PF‐C) by thaw‐erosion and deepening of the seasonally‐thawed active layer, and thereby promote PF‐C mineralization to CO2 and CH4. A similar PF‐C remobilization might have contributed to the increase in atmospheric CO2 during deglacial warming after the last glacial maximum. Using carbon...
Article
Full-text available
We investigated the morphology, biostratigraphy, shell stable isotope composition and paleogeography of the common Arctic benthic foraminifera, Cassidulina teretis (Tappan 1951) (sometimes assigned to Islandiella (Nørvang 1958), for application to Quaternary paleoceanography. Cassidulina teretis, which has been studied by several generations of Arc...
Conference Paper
Submarine cave is a cryptic system that was believed to be immune to external climate change. However, our study in a submarine cave in Okinawa has found that the benthic cave ecosystem could be affected by intensified East Asian Winter Monsoon, based on the synchronicity of species diversity of ostracods, foraminifers and bivalves and the paleocli...
Article
Full-text available
Calcareous microfossil assemblages in late Holocene sediments from the western Arctic continental shelf provide an important baseline for evaluating the impacts of today’s changing Arctic oceanography. This study compares ¹⁴C-dated late Holocene microfaunal assemblages of sediment cores SWERUS-L2-2-PC1, 2-MC4 and 2-KL1 (57 mwd), which record the la...
Article
We explore the use of Mg/Ca ratios in six Arctic Ocean benthic foraminifera species as bottom water palaeothermometers and expand published Mg/Ca-temperature calibrations to the coldest bottom temperatures (<1 °C). Foraminifera were analyzed in surface sediments at 27 sites in the Chukchi Sea, East Siberian Sea, Laptev Sea, Lomonosov Ridge and Pete...
Article
Full-text available
The Arctic Ocean is presently experiencing changes in ocean temperature and sea ice extent that are unprecedented in the observational time period (satellite observations: 1979-Present). To provide context for the current changes, scientists turn to paleo records of past climate to document and study natural variability in the Arctic system. Paleoc...
Article
Full-text available
Late Quaternary paleoceanographic changes at the Lomonosov Ridge, central Arctic Ocean, were reconstructed from a multicore and gravity core recovered during the 2014 SWERUS-C3 Expedition. Ostracode assemblages dated by accelerator mass spectrometry (AMS) indicate changing sea-ice conditions and warm Atlantic Water (AW) inflow to the Arctic Ocean f...
Article
This study presents a synthesis of century-scale hydroclimate variations in North America for the Common Era (last 2000 years) using new age models of previously published multiple proxy-based paleoclimate data. This North American Hydroclimate Synthesis (NAHS) examines regional hydroclimate patterns and related environmental indicators, including...
Article
Full-text available
Arctic Ocean temperatures influence ecosystems, sea ice, species diversity, biogeochemical cycling, seafloor methane stability, deep-sea circulation, and CO2 cycling. Today's Arctic Ocean and surrounding regions are undergoing climatic changes often attributed to "Arctic amplification" - that is, amplified warming in Arctic regions due to sea-ice l...
Article
Full-text available
Ice sheets extending over parts of the East Siberian continental shelf have been proposed for the last glacial period and during the larger Pleistocene glaciations. The sparse data available over this sector of the Arctic Ocean have left the timing, extent and even existence of these ice sheets largely unresolved. Here we present new geophysical ma...
Article
Full-text available
Deglacial (12.8–10.7 ka) sea level history on the East Siberian continental shelf and upper continental slope was reconstructed using new geophysical records and sediment cores taken during Leg 2 of the 2014 SWERUS-C3 expedition. The focus of this study is two cores from Herald Canyon, piston core SWERUS-L2-4-PC1 (4-PC1) and multicore SWERUS-L2-4-M...
Article
Full-text available
The Bering Strait connects the Arctic and Pacific oceans and separates the North American and Asian landmasses. The presently shallow ( ∼ 53 m) strait was exposed during the sea level lowstand of the last glacial period, which permitted human migration across a land bridge today referred to as the Bering Land Bridge. Proxy studies (stable isotope c...
Article
Full-text available
The Bering Strait connects the Arctic and Pacific oceans and separates the North American and Asian landmasses. The presently shallow ( ĝ1/4 53 m) strait was exposed during the sea level lowstand of the last glacial period, which permitted human migration across a land bridge today referred to as the Bering Land Bridge. Proxy studies (stable isotop...
Article
Full-text available
Ice sheets extending over parts of the East Siberian continental shelf have been proposed during the last glacial period, and during the larger Pleistocene glaciations. The sparse data available over this sector of the Arctic Ocean has left the timing, extent and even existence of these ice sheets largely unresolved. Here we present new geophysical...
Article
Full-text available
The caldera-forming eruption of the Aniakchak volcano in the Aleutian Range on the Alaskan Peninsula at 3.6 cal kyr BP was one of the largest Holocene eruptions worldwide. The resulting ash is found as a visible sediment layer in several Alaskan sites and as a cryptotephra on Newfoundland and Greenland. This large geographic distribution, combined...
Article
Full-text available
Deglacial (12.8–10.7 ka) sea-level history on the East Siberian continental shelf/upper continental slope was reconstructed using new geophysical records and sediment cores taken during Leg 2 of the 2014 SWERUS-C3 expedition. The focus of this study is two cores from Herald Canyon, piston core SWERUS-L2-4-PC1 (4-PC) and multicore SWERUS-L2-4-MC1 (4...
Chapter
Sediments provide one of the best reservoirs of information of how aquatic ecosystems have been altered by natural (climate change) and human agents over time. This information is preserved in a variety of biogenic materials including macro- and microfossils, pollen and chemical proxies, which record ecological responses to past perturbations. Ches...
Article
Full-text available
The Bering Strait connects the Arctic and Pacific oceans and separates the North American and Asian land masses. The presently shallow (~ 53 m) strait was exposed during the sea-level lowstand of the last glacial period, which permitted human migration across a land bridge referred to as Beringia. Proxy studies (stabile isotope composition of foram...
Article
Full-text available
A new Arctic Ostracode Database-2015 (AOD-2015) provides census data for 96 species of benthic marine Ostracoda from 1340 modern surface sediments from the Arctic Ocean and subarctic seas. Ostracoda is a meiofaunal, Crustacea group that secretes a bivalved calcareous (CaCO3) shell commonly preserved in sediments. Arctic and subarctic ostracode spec...
Article
The caldera-forming eruption of the Aniakchak volcano in the Aleutian Range on the Alaskan Peninsula at 3.6 cal 15 ka BP, was one of the largest Holocene eruptions worldwide. The resulting ash is found as a visible sediment layer in several Alaskan sites and as a cryptotephra on Newfoundland and Greenland. This large geographic distribution combine...
Poster
Full-text available
Shallow marine biodiversity patterns are governed by complicated combinations of environmental factors, and our understanding on the controlling mechanisms remains limited. Here we used ostracodes as a model system to look for the controlling factors on biodiversity patterns in shallow marine environments in the western North Atlantic Ocean and Arc...
Article
Full-text available
The caldera-forming eruption of the Aniakchak volcano in the Aleutian Range on the Alaskan Peninsula at 3.6 cal ka BP, was one of the largest Holocene eruptions worldwide. The resulting ash is found as a visible sediment layer in several Alaskan sites and as a cryptotephra on Newfoundland and Greenland. This large geographic distribution combined w...
Conference Paper
Rapidly retreating sea-ice in the arctic is one of many indicators of climate change. Since it controls processes that have repercussions on a variety of geographical scales, understanding of related mechanisms is imperative. In order to add to this knowledge, the expedition PS87 to the Central Arctic Ocean was conducted in 2014 and this study is b...
Article
Microfaunal and geochemical proxies from marine sediment records from central Arctic Ocean (CAO) submarine ridges suggest a close relationship over the last 550 thousand years (kyr) between orbital-scale climatic oscillations, sea-ice cover, marine biological productivity and other parameters. Multiple paleoclimate proxies record glacial to intergl...
Conference Paper
Full-text available
Latitudinal species diversity gradients (LSDGs) are a major feature of various marine groups. However, the detailed shape of LSDG in each marine taxonomic group and the causes of the diversity patterns, notably climatic factors, are still controversial due to limited sampling of many taxa in the world’s oceans. We analyzed benthic podocopid ostraco...
Article
Full-text available
The hypothesis of a km-thick ice shelf covering the entire Arctic Ocean during peak glacial conditions was proposed nearly half a century ago. Floating ice shelves preserve few direct traces after their disappearance, making reconstructions difficult. Seafloor imprints of ice shelves should, however, exist where ice grounded along their flow paths....
Presentation
Emerged Quaternary paleo-shorelines and marine deposits provide a more direct way to reconstruct and analyze the magnitude of relative sea-level (RSL) variability than methods using oxygen isotope analyses of deep ocean benthic foraminifera. Building on established lithostratigraphy and a newly revised uranium-series chronology for the coastal mari...