Wallace
Elizabeth J.
Wallace
Elizabeth J.
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ArticleRevising evidence of hurricane strikes on Abaco Island (the Bahamas) over the last 700 years(Nature Research, 2020-10-06) Winkler, Tyler S. ; van Hengstum, Peter J. ; Donnelly, Jeffrey P. ; Wallace, Elizabeth J. ; Sullivan, Richard M. ; MacDonald, Dana ; Albury, Nancy A.The northern Bahamas have experienced more frequent intense-hurricane impacts than almost anywhere else in the Atlantic since 1850 CE. In 2019, category 5 (Saffir-Simpson scale) Hurricane Dorian demonstrated the destructive potential of these natural hazards. Problematically, determining whether high hurricane activity levels remained constant through time is difficult given the short observational record (< 170 years). We present a 700-year long, near-annually resolved stratigraphic record of hurricane passage near Thatchpoint Blue Hole (TPBH) on Abaco Island, The Bahamas. Using longer sediment cores (888 cm) and more reliable age-control, this study revises and temporally expands a previous study from TPBH that underestimated the sedimentation rate. TPBH records at least 13 ≥ category 2 hurricanes per century between 1500 to 1670 CE, which exceeds the 9 ≥ category 2 hurricanes per century within 50 km of TPBH since 1850 CE. The eastern United States also experienced frequent hurricanes from 1500 to 1670 CE, but frequency was depressed elsewhere in the Atlantic Ocean. This suggests that spatial heterogeneity in Atlantic hurricane activity since 1850 CE could have persisted throughout the last millennium. This heterogeneity is impacted by climatic and stochastic forcing, but additional high-resolution paleo-hurricane reconstructions are required to assess the mechanisms that impact regional variability.
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ArticleLabeling poststorm coastal imagery for machine learning: measurement of interrater agreement(American Geophysical Union, 2021-09-03) Goldstein, Evan B. ; Buscombe, Daniel ; Lazarus, Eli ; Mohanty, Somya D. ; Rafique, Shah Nafis ; Anarde, Katherine A. ; Ashton, Andrew D. ; Beuzen, Tomas ; Castagno, Katherine ; Cohn, Nicholas ; Conlin, Matthew P. ; Ellenson, Ashley ; Gillen, Megan N. ; Hovenga, Paige A. ; Over, Jin-Si ; Palermo, Rose V. ; Ratliff, Katherine M. ; Reeves, Ian R. B. ; Sanborn, Lily H. ; Straub, Jessamin A. ; Taylor, Luke A. ; Wallace, Elizabeth J. ; Warrick, Jonathan ; Wernette, Phillipe ; Williams, Hannah E.Classifying images using supervised machine learning (ML) relies on labeled training data—classes or text descriptions, for example, associated with each image. Data-driven models are only as good as the data used for training, and this points to the importance of high-quality labeled data for developing a ML model that has predictive skill. Labeling data is typically a time-consuming, manual process. Here, we investigate the process of labeling data, with a specific focus on coastal aerial imagery captured in the wake of hurricanes that affected the Atlantic and Gulf Coasts of the United States. The imagery data set is a rich observational record of storm impacts and coastal change, but the imagery requires labeling to render that information accessible. We created an online interface that served labelers a stream of images and a fixed set of questions. A total of 1,600 images were labeled by at least two or as many as seven coastal scientists. We used the resulting data set to investigate interrater agreement: the extent to which labelers labeled each image similarly. Interrater agreement scores, assessed with percent agreement and Krippendorff's alpha, are higher when the questions posed to labelers are relatively simple, when the labelers are provided with a user manual, and when images are smaller. Experiments in interrater agreement point toward the benefit of multiple labelers for understanding the uncertainty in labeling data for machine learning research.
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ArticleIntense hurricane activity over the past 1500 years at South Andros Island, the Bahamas(American Geophysical Union, 2019-10-19) Wallace, Elizabeth J. ; Donnelly, Jeffrey P. ; van Hengstum, Peter J. ; Wiman, Charlotte ; Sullivan, Richard M. ; Winkler, Tyler S. ; D'Entremont, Nicole ; Toomey, Michael R. ; Albury, Nancy A.Hurricanes cause substantial loss of life and resources in coastal areas. Unfortunately, historical hurricane records are too short and incomplete to capture hurricane‐climate interactions on multi‐decadal and longer timescales. Coarse‐grained, hurricane‐induced deposits preserved in blue holes in the Caribbean can provide records of past hurricane activity extending back thousands of years. Here we present a high resolution record of intense hurricane events over the past 1500 years from a blue hole on South Andros Island on the Great Bahama Bank. This record is corroborated by shorter reconstructions from cores collected at two nearby blue holes. The record contains coarse‐grained event deposits attributable to known historical hurricane strikes within age uncertainties. Over the past 1500 years, South Andros shows evidence of four active periods of hurricane activity. None of these active intervals occurred in the past 163 years. We suggest that Intertropical Convergence Zone position modulates hurricane activity on the island based on a correlation with Cariaco Basin titanium concentrations. An anomalous gap in activity on South Andros Island in the early 13th century corresponds to a period of increased volcanism. The patterns of hurricane activity reconstructed from South Andros Island closely match those from the northeastern Gulf of Mexico but are anti‐phased with records from New England. We suggest that either changes in local environmental conditions (e.g., SSTs) or a northeastward shift in storm tracks can account for the increased activity in the western North Atlantic when the Gulf of Mexico and southeastern Caribbean are less active.
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Article1,050 years of hurricane strikes on Long Island in the Bahamas(American Geophysical Union, 2016-02-16) Wallace, Elizabeth J. ; Donnelly, Jeffrey P. ; van Hengstum, Peter J. ; Winkler, Tyler S. ; McKeon, Kelly ; MacDonald, Dana ; D'Entremont, Nicole ; Sullivan, Richard M. ; Woodruff, Jonathan D. ; Hawkes, Andrea D. ; Maio, Christopher V.Sedimentary records of past hurricane activity indicate centennial-scale periods over the past millennium with elevated hurricane activity. The search for the underlying mechanism behind these active hurricane periods is confounded by regional variations in their timing. Here, we present a new high resolution paleohurricane record from The Bahamas with a synthesis of published North Atlantic records over the past millennium. We reconstruct hurricane strikes over the past 1,050 years in sediment cores from a blue hole on Long Island in The Bahamas. Coarse-grained deposits in these cores date to the close passage of seven hurricanes over the historical interval. We find that the intensity and angle of approach of these historical storms plays an important role in inducing storm surge near the site. Our new record indicates four active hurricane periods on Long Island that conflict with published records on neighboring islands (Andros and Abaco Island). We demonstrate these three islands do not sample the same storms despite their proximity, and we compile these reconstructions together to create the first regional compilation of annually resolved paleohurricane records in The Bahamas. Integrating our Bahamian compilation with compiled records from the U.S. coastline indicates basin-wide increased storminess during the Medieval Warm Period. Afterward, the hurricane patterns in our Bahamian compilation match those reconstructed along the U.S. East Coast but not in the northeastern Gulf of Mexico. This disconnect may result from shifts in local environmental conditions in the North Atlantic or shifts in hurricane populations from straight-moving to recurving storms over the past millennium.
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ArticleHistorically unprecedented Northern Gulf of Mexico hurricane activity from 650 to 1250 CE(Nature Research, 2020-11-05) Rodysill, Jessica R. ; Donnelly, Jeffrey P. ; Sullivan, Richard M. ; Lane, D. Philip ; Toomey, Michael R. ; Woodruff, Jonathan D. ; Hawkes, Andrea D. ; MacDonald, Dana ; D'Entremont, Nicole ; McKeon, Kelly ; Wallace, Elizabeth J. ; van Hengstum, Peter J.Hurricane Michael (2018) was the first Category 5 storm on record to make landfall on the Florida panhandle since at least 1851 CE (Common Era), and it resulted in the loss of 59 lives and $25 billion in damages across the southeastern U.S. This event placed a spotlight on recent intense (exceeding Category 4 or 5 on the Saffir-Simpson Hurricane Wind Scale) hurricane landfalls, prompting questions about the natural range in variability of hurricane activity that the instrumental record is too short to address. Of particular interest is determining whether the frequency of recent intense hurricane landfalls in the northern Gulf of Mexico (GOM) is within or outside the natural range of intense hurricane activity prior to 1851 CE. In this study, we identify intense hurricane landfalls in northwest Florida during the past 2000 years based on coarse anomaly event detection from two coastal lacustrine sediment archives. We identified a historically unprecedented period of heightened storm activity common to four Florida panhandle localities from 650 to 1250 CE and a shift to a relatively quiescent storm climate in the GOM spanning the past six centuries. Our study provides long-term context for events like Hurricane Michael and suggests that the observational period 1851 CE to present may underrepresent the natural range in landfalling hurricane activity.
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ThesisHigh resolution sedimentary archives of past millennium hurricane activity in the Bahama Archipelago(Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2020-09) Wallace, Elizabeth J.Little is known about how Atlantic hurricane activity changes on long timescales. This thesis uses proxy development and proxy-model integration to constrain the spatiotemporal variability in hurricane activity in the Bahama Archipelago over the past millennium. I present annually-resolved archives of storm activity derived from sediment cores from blue holes on three islands in the Bahama Archipelago: South Andros, Long Island, and Middle Caicos. Dramatic differences between these records suggest localized controls on the hurricane patterns observed by each island. Thus, compiling these records together more accurately captures regional variations in hurricane strikes. Integrating our new Bahama Archipelago compilation with compiled paleohurricane records from the U.S. coastline indicates shifting patterns of hurricane activity over the past millennium between the Gulf Coast and the Bahama Archipelago/New England. Finally, I address whether variability in hurricane strikes observed in Bahamian paleohurricane records is related to climate or random variability using hurricane model output. The signal observed in any individual record of paleohurricane activity from the Bahama Archipelago is driven more by random variability in hurricane tracks than by climate. This thesis lays the groundwork for creating high-resolution paleohurricane records from blue holes and using hurricane models to inform our interpretations of these records.
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ArticleMore Frequent Hurricane Passage Across the Bahamian Archipelago During the Little Ice Age(American Geophysical Union, 2023-11-21) Winkler, Tyler S. ; van Hengstum, Peter J. ; Donnelly, Jeffrey P. ; Wallace, Elizabeth Jane ; Albury, Nancy A. ; D'Entremont, Nicole ; Hawkes, Andrea D. ; Maio, Christopher V. ; Roberts, J. ; Sullivan, Richard M. ; Woodruff, Jonathan D.The year 2020 Common Era (CE) experienced the highest number of named tropical cyclones in the Atlantic Ocean since 1850 CE, but the short instrumental record makes it challenging to assess if this level of activity is statistically meaningful. Here, we present two near-annually resolved hurricane reconstructions from sediment archived in two blue holes located only 300 m apart on the northern margin of Grand Bahama. These two blue holes provide a replicated signal of hurricanes passing within a 50–100 km radius over the last 1,800 years, and the long-term reconstructions document multiple 50-to-150-year intervals when hurricane frequency was significantly higher than it has been over the last 100 years. These two records were first merged into a single stack, and then compiled with five other high-resolution reconstructions from across the Bahamian Archipelago to form a single 1500-year record of Bahamian hurricane frequency. This new Bahamian Compilation documents more hurricanes passing ∼75°W from 21°N to 26°N during the Little Ice Age (LIA; 1300–1850 CE) relative to the prior millennium and the last 170 years. The US Eastern Seaboard also experienced heightened hurricane activity during the LIA, whereas the Gulf of Mexico and Southern Caribbean were inactive. This suggests that despite a globally cooler climate, regional climate conditions during the LIA remained favorable for cyclogenesis and intensification along certain Atlantic hurricane pathways. Perhaps heightened Sahel rainfall during the LIA indicates an increase in African Easterly waves, which in turn possibly seeded more tropical cyclones in the Atlantic Main Development Region.
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ArticleIntegrating climatological‐hydrodynamic modeling and paleohurricane records to assess storm surge risk(American Geophysical Union, 2024-01-25) Begmohammadi, Amirhosein ; Blackshaw, Christine Y. ; Lin, Ning ; Gori, Avantika ; Wallace, Elizabeth J. ; Emanuel, Kerry A. ; Donnelly, Jeffrey P.Sediment cores from blue holes have emerged as a promising tool for extending the record of long-term tropical cyclone (TC) activity. However, interpreting this archive is challenging because storm surge depends on many parameters including TC intensity, track, and size. In this study, we use climatological-hydrodynamic modeling to interpret paleohurricane sediment records between 1851 and 2016 and assess the storm surge risk for Long Island in The Bahamas. As the historical TC data from 1988 to 2016 is too limited to estimate the surge risk for this area, we use historical event attribution in paleorecords paired with synthetic storm modeling to estimate TC parameters that are often lacking in earlier historical records (i.e., the radius of maximum wind for storms before 1988). We then reconstruct storm surges at the sediment site for a longer time period of 1851–2016 (the extent of hurricane Best Track records). The reconstructed surges are used to verify and bias-correct the climatological-hydrodynamic modeling results. The analysis reveals a significant risk for Long Island in The Bahamas, with an estimated 500-year stormtide of around 1.63 ± 0.26 m, slightly exceeding the largest recorded level at site between 1988 and 2015. Finally, we apply the bias-corrected climatological-hydrodynamic modeling to quantify the surge risk under two carbon emission scenarios. Due to sea level rise and TC climatology change, the 500-year stormtide would become 2.69 ± 0.50 and 3.29 ± 0.82 m for SSP2-4.5 and SSP5-8.5, respectively by the end of the 21st century.
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ArticleLast millennium hurricane activity linked to endogenous climate variability(Nature Research, 2024-01-27) Yang, Wenchang ; Wallace, Elizabeth J. ; Vecchi, Gabriel A. ; Donnelly, Jeffrey P. ; Emile-Geay, Julien ; Hakim, Gregory J. ; Horowitz, Larry W. ; Sullivan, Richard M. ; Tardif, Robert ; van Hengstum, Peter J. ; Winkler, Tyler S.Despite increased Atlantic hurricane risk, projected trends in hurricane frequency in the warming climate are still highly uncertain, mainly due to short instrumental record that limits our understanding of hurricane activity and its relationship to climate. Here we extend the record to the last millennium using two independent estimates: a reconstruction from sedimentary paleohurricane records and a statistical model of hurricane activity using sea surface temperatures (SSTs). We find statistically significant agreement between the two estimates and the late 20th century hurricane frequency is within the range seen over the past millennium. Numerical simulations using a hurricane-permitting climate model suggest that hurricane activity was likely driven by endogenous climate variability and linked to anomalous SSTs of warm Atlantic and cold Pacific. Volcanic eruptions can induce peaks in hurricane activity, but such peaks would likely be too weak to be detected in the proxy record due to large endogenous variability.