Penguin Dynamics And Its Influencing Factors In Antarctic Typical Regions Over The Past Two Millennia

At the top of the Southern Ocean food chain,penguins are typical marine life in the Antarctica.They breed in ice-free areas and prey on the Southern Ocean,so they are very sensitive to terrestrial and marine environmental changes.Penguin demographics,feeding behavior,and breeding habitats have important implications for Antarctic climate,environment,and marine ecosystems.In-depth study of the response patterns of penguin ecological history to climate change has important scientific value and help to understand and predict the impact of future climate change to Antarctic ecology.In this study we used ornithogenic sediment profiles as well as the penguin residues(penguin feathers,bones,etc.)as carriers,which are taken from modern and abandoned penguin colonies in the Ross Sea and the Antarctic Peninsula.By applying multidisciplinary research that combine elements,stable isotopes,biogeochemistry,paleoclimate,and atmospheric science,we inferred the historical changes of penguin populations,and focused on the spatial and temporal distribution pattern of penguin breeding habitats in both places since the late Holocene and their responses to large-scale climate variability and the driving mechanisms.1.Penguin dynamics and its driving mecthanisim during the Little Ice Age in Cape Bird,Ross IslandUsing ornithogenic sediments(CB2)at Cape Bird,Ross Island,Antarctica,we inferred relative population changes of Adelie penguins in the southern Ross Sea over the past 500 years,and observed an increase in penguin populations during the Little Ice Age(LIA;1500-1850 AD).We used cadmium content in ancient penguin guano as a proxy of ocean upwelling and identified a close linkage between penguin dynanmics and atmospheric circulation and oceanic conditions.During the cold priod of 1600-1825 AD,a deepened Amundscen Sea Low(ASL)led to stronger winds.intensified ocean upwelling,enlarged Ross Sea and McMurdo Sound polynyas,and thus higher food abundance and penguin populations.We propose a mechanism linking Antarctic marine ecology and atmospheric/oceanic dynamics which can help explain and predict responses of Antarctic high latitudes ecosystems to climate change.2.Penguin dynamics during the past two millennia in the Scott Coast,the southern Ross SeaGeochronological and elemental geochemical analyses were performed on sediment profiles(CRIK DII)that collected from Cape Ross and Dunlop Island in Scott Coast,the southern Ross Sea.The results show that piedmont glacier advanced at?2000 yr BP in the Ross Sea region(at least in the Cape Ross)and coincided with the climate records of the Neoglacial period in the Antarctic Peninsula and the East Antarctica.Therefore,it is possible to define the time of the Neoglacial in the Ross Sea,and provide supplement and argument for late Holocene climate change in this region.This late Holocene glaciers advancement have caused penguin colonies abandonment in most parts of the Scott Coast,but the penguin occupation on Dunlop Island has not been interrupted because of the terrain barrier,and currently this island is the only found penguin refuge in Scott Coast during the late Holocene.With the colonies abandoned in most part of the Scott Coast,penguins reoccupied other relatively suitable habitats in the Ross Sea.The migration route is roughly divided into three categories:northward to Cape Adare,southward to Ross Island,and to Terra Nova Bay area,and is closely related to sea ice,ocean currents,polynya,and katabatic winds.3.Penguin occupation and depositional environmental events in Cape Crozier,Ross IslandUsing ornithogenic sediment(CC2)that taken from Cape Crozier,Ross Island.we showed that Adlie penguins occupied on Cape Crozier around 1140 yr BP.reflecting the relatively warmer climate and declining sea ice at that time,corresponds to the Medieval Warm Period(MWP).Since then,the penguin population record has been interrupted due to a huge change in the sedimentary environment.Therefore,when using TOC and typical bio-elements to reconstruct penguin populations during the historical period.it should be comprehensive consideration of factors such as topography and climate change,and sample collection should be at flat terrain and within catchment.In addition,we pointed out that anomaly snowmelt or precipitation is the most likely causes for the instantaneous deposition events occurring during 800-600 yr BP in Cape Crozier.More high-resolution sediments,ice cores and other climate records are needed in the future to further study the driving mechanisms of these rapid climate change events.4.Enhanced westerlies likely drove the penguin migration around 1000 yr BP at Ardley Island,west Antarctic PeninsulaWe collected an ornithogenic sediment profile(Ql)and reconstructed penguins'occupation history in the eastern part of Ardley Island for the first time.Penguins inhabited the eastern part at least about 500 yr BP,and penguin populations significantly increased during the LIA.In the western part,penguins started to abandon the colonies since 1000 yr BP.This migration is likely driven by SAM's shift towards positive phase,which induces stronger westerly winds and consequently drive penguins to the more sheltered eastern side.At least at Ardley Island,temperature is not the only factor determining penguin colonies and populations;the island topography,wind and snow patterns,and large-scale climate forcing could play an important role as well.This study provides a new perspective for investigating atmospheric circulation and paleoecology in historical context and assessing the possible impact of future climate change on penguins breeding habitats;it is also of reference value for the safety of Penguin Ecological Reserve.