Browsing by Author "Skrzypek, G"

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    Evidence for extreme floods in arid subtropical northwest Australia during the Little Ice Age chronozone (CE 1400-1850).
    (Elsevier, 2016-07-15) Rouillard, A; Skrzypek, G; Turney, CSM; Dorgramaci, S; Hua, Q; Zawadzki, A; Reeves, JM; Greenwood, P; O’Donnell, AJ; Grierson, PF
    Here we report a ∼2000-year sediment sequence from the Fortescue Marsh (Martuyitha) in the eastern Pilbara region, which we have used to investigate changing hydroclimatic conditions in the arid subtropics of northwest Australia. The Pilbara is located at the intersection of the tropical Indian and Pacific Oceans and its modern rainfall regime is strongly influenced by tropical cyclones, the Intertropical Convergence Zone (ITCZ) and the Indo-Pacific Warm Pool. We identified four distinct periods within the record. The most recent period (P1: CE ∼1990–present) reveals hydroclimatic conditions over recent decades that are the most persistently wet of potentially the last ∼2000 years. During the previous centuries (P2: ∼CE 1600–1990), the Fortescue Marsh was overall drier but likely punctuated by a number of extreme floods, which are defined here as extraordinary, strongly episodic floods in drylands generated by rainfall events of high volume and intensity. The occurrence of extreme floods during this period, which encompasses the Little Ice Age (LIA; CE 1400–1850), is coherent with other southern tropical datasets along the ITCZ over the last 2000 years, suggesting synchronous hydroclimatic changes across the region. This extreme flood period was preceded by several hundred years (P3: ∼CE 700–1600) of less vigorous but more regular flows. The earliest period of the sediment record (P4: ∼CE 100–700) was the most arid, with sedimentary and preservation processes driven by prolonged drought. Our results highlight the importance of developing paleoclimate records from the tropical and sub-tropical arid zone, providing a long-term baseline of hydrological conditions in areas with limited historical observations. © 2016 Elsevier Ltd.
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    Identifying nitrogen limitations to organic sediments accumulation in various vegetation types of arctic tundra (Hornsund, Svalbard)
    (American Geophysical Union, 2015-12-15) Skrzypek, G; Wojtuń, B; Hua, Q; Richter, R; Jakubas, D; Wojczulanis–Jakubas, K; Samecka–Cymerman, A
    Arctic and subarctic regions play important roles in the global carbon balance. However, nitrogen (N) deficiency is a major constraint for organic carbon sequestration in the High Arctic. Hence, the identification of the relative contributions from different N-sources is critical for understanding the constraints that limit tundra growth. The stable nitrogen composition of the three main N-sources and numerous plants were analyzed in ten tundra types in the Fuglebekken catchment (Hornsund Fjord, Svalbard, 77°N 15°E). The percentage of the total tundra N-pool provided by seabirds’ feces (colonially breeding, planktivorous Alle alle), ranged from 0–21% in Patterned-ground tundra to 100% in Ornithocoprophilous tundra. The total N-pool utilized by tundra plants in the studied catchment was built in 36% by birds, 38% by atmospheric deposition, and 26% by N2-fixation. The results clearly show that N-pool in the tundra is significantly supplemented by nesting seabirds. Thus, if they experienced substantial negative environmental pressure associated with climate change, it would adversely influence the tundra N-budget [1]. The growth rates and the sediment thickness (<15 cm) in different tundra types varied considerably but the tundra age was similar, <450 cal BP. The only exception was Ornithocoprophilous tundra with very diverse ages ranging from 235 to 2300 cal BP and thickness up to 110cm. The growth rates for this tundra (62 cm core, 18 AMS 14C dates) were high (1.5-3.0 mm/yr) between 1568 and 1804 AD and then substantially declined for the period between 1804 and 1929 AD (0.2 mm/yr). These findings deliver an additional argument, that the organic matter accumulation is driven not only directly by climatic conditions but also by birds’ contribution to the tundra N-pool. © 2014, American Geophysical Union.
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    Variation in bird’s originating nitrogen availability limits high arctic tundra development over last 2000 year (Hornsund, Svalbard)
    (European Geosciences Union, 2016-04-20) Skrzypek, G; Wojtún, B; Hua, Q; Richter, D; Jakubas, D; Wojczulanis–Jakubas, K; Samecka–Cymerman, A
    Arctic and subarctic regions play important roles in the global carbon balance. However, nitrogen (N) defi-ciency is a major constraint for organic carbon sequestration in the High Arctic. Hence, the identification of therelative contributions from different N-sources is critical for understanding the constraints that limit tundra growth.The stable nitrogen composition of the three main N-sources and numerous plants were analyzed in tentundra types (including those influenced by seabirds) in the Fuglebekken catchment (Hornsund, Svalbard, 77◦N15◦E). The percentage of the total tundra N-pool provided by seabirds’ feces (from planktivorous coloniallybreeding little auks Alle alle), ranged from 0–21% in Patterned-ground tundra to 100% in Ornithocoprophiloustundra. The total N-pool utilized by tundra plants in the studied catchment originated from birds (36%),atmospheric deposition (38%), and N2-fixation (26%). The results clearly show that N-pool in the tundra issignificantly supplemented by nesting seabirds. Thus, if they experienced climate change induced substantialnegative environmental pressure, it would adversely influence the tundra N-budget (Skrzypek et al. 2015).The growth rates and the sediment thickness (<15cm) in different tundra types varied considerably but thetundra age was similar in the whole area, <450 cal BP. The only exception was Ornithocoprophilous bird-N richtundra with very diverse ages ranging from 235 to 2300 cal BP and thickness up to 110 cm. The growth rates forthis tundra (62 cm core, 18 AMS 14C dates) were high (1.5-3.0 mm/yr) between 1568 and 1804 AD and thensubstantially declined for the period between 1804 and 1929 AD (0.2 mm/yr). These findings deliver an additionalargument, that the organic matter accumulation is driven not only directly by climatic conditions but also by birds’contribution to the tundra N-pool. © 2016 Author(s)