Using Paleoecological Proxies to Determine Holocene Environmental Change: A Case Study at Onaero Beach, North Taranaki

<p>A multi-proxy paleoecological and sedimentological record for the last ~8.3kyr is extracted from a 2.1m coastal seacliff at Onaero Beach, North Taranaki. This record is used to infer both local environmental changes including shoreline, coastal conditions, as well as regional changes in atmospheric circulation and climate wetness. Analysis of diatom and pollen populations, particle size, and loss on ignition provide the raw data from which inferences regarding salinity and vegetation are made. Changes are tied to a chronology determined through radiocarbon ages and tephrochronology. Key objectives of this study are: (1) To characterize changes in salinity and relative shoreline position at Onaero Beach (2) To characterise changes in vegetation and relate these changes to overall state of the climate through the Holocene (3) Compare the results of this study with others from New Zealand and the wider south pacific to investigate how the Onaero Beach section fits in both a regional and global context. Diatom analysis of the Onaero section revealed the dominance of brackish to marine species which suddenly at 7.3ka after which time diatom assemblages were dominated by fresh and salt intolerant species. The marine to freshwater transition represents a transition from a brackish to freshwater coastal lagoon. Pollen analysis of the Onaero Beach section indicates the region was dominated by podocarp forest. The increasing dominance of Dacrydium and decline in other podocarps suggests an increase in overall climate wetness. The disappearance of pollen in conjunction with the deposition of tephra at ~4.15ka is not conclusive proof of, but certainly fits with, the idea of a significant climatic event occurring at ~4.2ka resulting in a reversal of the current prevailing wind direction and supports the case for a formal Middle/Late Holocene boundary at this time.</p>

Using Paleoecological Proxies to Determine Holocene Environmental Change: A Case Study at Onaero Beach, North Taranaki

<p>A multi-proxy paleoecological and sedimentological record for the last ~8.3kyr is extracted from a 2.1m coastal seacliff at Onaero Beach, North Taranaki. This record is used to infer both local environmental changes including shoreline, coastal conditions, as well as regional changes in atmospheric circulation and climate wetness. Analysis of diatom and pollen populations, particle size, and loss on ignition provide the raw data from which inferences regarding salinity and vegetation are made. Changes are tied to a chronology determined through radiocarbon ages and tephrochronology. Key objectives of this study are: (1) To characterize changes in salinity and relative shoreline position at Onaero Beach (2) To characterise changes in vegetation and relate these changes to overall state of the climate through the Holocene (3) Compare the results of this study with others from New Zealand and the wider south pacific to investigate how the Onaero Beach section fits in both a regional and global context. Diatom analysis of the Onaero section revealed the dominance of brackish to marine species which suddenly at 7.3ka after which time diatom assemblages were dominated by fresh and salt intolerant species. The marine to freshwater transition represents a transition from a brackish to freshwater coastal lagoon. Pollen analysis of the Onaero Beach section indicates the region was dominated by podocarp forest. The increasing dominance of Dacrydium and decline in other podocarps suggests an increase in overall climate wetness. The disappearance of pollen in conjunction with the deposition of tephra at ~4.15ka is not conclusive proof of, but certainly fits with, the idea of a significant climatic event occurring at ~4.2ka resulting in a reversal of the current prevailing wind direction and supports the case for a formal Middle/Late Holocene boundary at this time.</p>

Landings of Acetes spp. in the east coast of Sabah in the past 30 years (1990-2019)

The genus Acetes is a minor planktonic crustacean group, known by locals as ‘Udang Geragau’, ‘Udang Baring’ or ‘Bubok’ in different parts of Malaysia. The main objective of this research is to study the impact of climatic events on Acetes spp. landings at the East Coast of Sabah waters (Kudat and Tawau) in the past 30 years (1990-2019). Landing data on Acetes was obtained from the Fisheries Department of Sabah, Malaysia while the climatic data were provided by Malaysian Meteorological Department. One-way ANOVA analyses were conducted on the mean temperature, relative humidity, rainfall and the annual landings of Acetes spp. Pearson’s correlation test was later performed to measure relationship between the annual Acetes spp. landings and the variables as mentioned above. The results of correlation tests revealed that two variables (mean temperature and relative humidity) were having weak negative correlations with the annual landings in Kudat. Mean annual rainfall showed weak positive correlation with the Acetes landings in Tawau. The present study showed that changes in climatic event does influence the annual landings of Acetes spp. in the East Coast of Sabah.

Evaluating The Temporal Relationship Between Climatic and Demographic Events Using Radiocarbon Data: A Case-Study From The Chulmun Period, Korea

We investigate the relationship between climatic and demographic events in Korea during the Chulmun period (10,000–3,500 cal. BP) by analyzing paleoenvironmental proxies and 14C dates. We focus on testing whether a cooling climate, and its potential impact on millet productivity around 4,500 cal. BP triggered the population decline observed in the archaeological record. We employ a Bayesian approach that measures the temporal relationship between climatic events and change-points in the rate of growth in human population as inferred by radiocarbon density. Our results do not support the climate-induced population decline hypothesis for three reasons. First, we could not determine that the cooling climatic event necessarily preceded the reversal point in population growth rate as inferred by the radiocarbon record. Second, we did not find evidence showing a significant reduction of millet-associated dates occurring during the cooling climate. Third, we detected a spatially differentiated pattern of decline in inland and coastal regions, indicating that the cooling climate did not impact all populations equally. We highlighted the long tradition of mobility-based subsistence strategy in the coastal region as a potential factor contributing to the spatial differences.

Detecting transience in slow evolution landscapes using cosmogenic nuclides and high resolution morphometry

&lt;p&gt;Transient evolution and adjustment to changing tectonic and climatic boundary conditions is an essential attribute of landscapes. We present a new approach to detect and quantify transience in slow erosion landscapes over 100 ka timescales. We compare curvature and cosmogenic nuclides measurements (&lt;sup&gt;10&lt;/sup&gt;Be and &lt;sup&gt;26&lt;/sup&gt;Al) at hilltop sites with predictions of hillslope diffusion theory, in the slowly evolving quartzitic Serra do Cip&amp;#243; range in SE Brazil, and we observe a distinctive signature of an acceleration of denudation. The timing of this increase cannot be unequivocally associated with a single climatic event but is consistent with climatically-modulated important fluctuations in precipitation and erosion in this area during Middle and Late Pleistocene.&lt;/p&gt;