Paleo-oceanographic and -climatic reconstruction in the Southwest Pacific [ODP Site 1123] during MIS 11

<p>Marine Isotope Stage 11 [424 to 374 ka] is unique compared to most other recent Quaternary interglacial periods due to its duration and orbital geometry, both of which have previously been cited as evidence that MIS 11 may be a suitable analogue to project future climate. This study aims to evaluate this prolonged warm period at a key site in the sparsely studied Southwest Pacific Ocean at Ocean Drilling Program [ODP] 1123. This cored site, situated at 3290 m water depth on the northern flank of the Chatham Rise, straddles the northern limit of the modern Subtropical Front, 1100 km east of New Zealand, where sediments record strong subtropical and subpolar signals over interglacial to glacial cycles. Two species of planktonic foraminifera were analysed, Globigerinoides ruber and Globigerina bulloides [Gs. ruber and Gg. bulloides], for trace elements and size-normalised test weights [SNW; Gg. bulloides only] in order to reconstruct ocean temperature, chemistry, structure and circulation during MIS 11. Gg. bulloides was found to have anomalously low SNW [~50% compared to modern specimens] implying either [i] poor calcification environment due to low CO₃⁻² concentrations, or [ii] post-mortem alteration either in the deep water column or ocean floor environment. Traditional dissolution proxies for ODP 1123 do not indicate significant dissolution during MIS 11. Nevertheless, the inception of modern carbonate platforms and reefs at this time leads to the hypothesis that CO₃⁻² concentrations in the surface ocean were low due to a shifting in the locus of carbonate production, and this is a potential cause, amongst other possibilities, of the low SNW in Gg. bulloides. However, calcification in a low CO₃⁻² concentration ocean does not appear to have significantly affected the geochemical proxies utilised in this study [Mg/Ca-derived paleo-ocean temperatures, δ¹⁸O and micro-nutrients Mn/Ca and Zn/Ca ratios as water-mass tracers] based on comparison with a similar study on younger sediments in the same core. The temperature difference between Gs. ruber and Gg. bulloides is the same as the modern temperature difference at ODP 1123, implying that Gs.ruber was also not markedly affected by either low CO₃⁻² concentrations during calcification or post-mortem dissolution. Laser ablation inductively coupled plasma mass spectrometry is utalised to measure in situ trace element ratios [Mg, Al, Ca, Mn, Zn and Sr/Ca], and reconstruct the thermal structure of the ocean’s upper 200 m. The main findings are [i] a well stratified upper ocean in warm periods punctuated by well mixed waters in cooler and presumably windier conditions; [ii] an invigorated South Pacific Gyre during the prolonged MIS 11 interglacial, resulting in a greater inflow of subtropical water to ODP 1123 as evinced by Mn/Ca and Zn/Ca ratios and supported by elevated subtropical foramiferal assemblages; [iii] paleo-ocean temperatures that indicate the mean MIS 11 sea surface temperature optimum was ca. 2°C warmer than present; and [iv] a spike in productivity is identified by elevated Mn/Ca and Zn/Ca ratios at ca. 400 ka, coinciding with a spike in eutrophic species abundance, indicating a period of significantly enhanced subtropical water influence. Records from other New Zealand sites reveal MIS 11 as a prolonged [up to 40 kyr] interglacial period, following a rapid and pronounced 10°C warming from the MIS 12 glacial. Deglaciation occurred 13 kyr earlier than the global benthic record. This rise was punctuated by an Antarctic Cold Reversal-like cooling confirming episodic sub-polar influences at the site. Some differences between the orbital configurations of MIS 1 and 11, particularly at the precessional scale, coupled with apparently unusual ocean chemistry [e.g., low CO₃⁻²] during MIS 11, suggest that MIS 11 may not be an ideal analogue for the Holocene.</p>

Paleo-oceanographic and -climatic reconstruction in the Southwest Pacific [ODP Site 1123] during MIS 11

<p>Marine Isotope Stage 11 [424 to 374 ka] is unique compared to most other recent Quaternary interglacial periods due to its duration and orbital geometry, both of which have previously been cited as evidence that MIS 11 may be a suitable analogue to project future climate. This study aims to evaluate this prolonged warm period at a key site in the sparsely studied Southwest Pacific Ocean at Ocean Drilling Program [ODP] 1123. This cored site, situated at 3290 m water depth on the northern flank of the Chatham Rise, straddles the northern limit of the modern Subtropical Front, 1100 km east of New Zealand, where sediments record strong subtropical and subpolar signals over interglacial to glacial cycles. Two species of planktonic foraminifera were analysed, Globigerinoides ruber and Globigerina bulloides [Gs. ruber and Gg. bulloides], for trace elements and size-normalised test weights [SNW; Gg. bulloides only] in order to reconstruct ocean temperature, chemistry, structure and circulation during MIS 11. Gg. bulloides was found to have anomalously low SNW [~50% compared to modern specimens] implying either [i] poor calcification environment due to low CO₃⁻² concentrations, or [ii] post-mortem alteration either in the deep water column or ocean floor environment. Traditional dissolution proxies for ODP 1123 do not indicate significant dissolution during MIS 11. Nevertheless, the inception of modern carbonate platforms and reefs at this time leads to the hypothesis that CO₃⁻² concentrations in the surface ocean were low due to a shifting in the locus of carbonate production, and this is a potential cause, amongst other possibilities, of the low SNW in Gg. bulloides. However, calcification in a low CO₃⁻² concentration ocean does not appear to have significantly affected the geochemical proxies utilised in this study [Mg/Ca-derived paleo-ocean temperatures, δ¹⁸O and micro-nutrients Mn/Ca and Zn/Ca ratios as water-mass tracers] based on comparison with a similar study on younger sediments in the same core. The temperature difference between Gs. ruber and Gg. bulloides is the same as the modern temperature difference at ODP 1123, implying that Gs.ruber was also not markedly affected by either low CO₃⁻² concentrations during calcification or post-mortem dissolution. Laser ablation inductively coupled plasma mass spectrometry is utalised to measure in situ trace element ratios [Mg, Al, Ca, Mn, Zn and Sr/Ca], and reconstruct the thermal structure of the ocean’s upper 200 m. The main findings are [i] a well stratified upper ocean in warm periods punctuated by well mixed waters in cooler and presumably windier conditions; [ii] an invigorated South Pacific Gyre during the prolonged MIS 11 interglacial, resulting in a greater inflow of subtropical water to ODP 1123 as evinced by Mn/Ca and Zn/Ca ratios and supported by elevated subtropical foramiferal assemblages; [iii] paleo-ocean temperatures that indicate the mean MIS 11 sea surface temperature optimum was ca. 2°C warmer than present; and [iv] a spike in productivity is identified by elevated Mn/Ca and Zn/Ca ratios at ca. 400 ka, coinciding with a spike in eutrophic species abundance, indicating a period of significantly enhanced subtropical water influence. Records from other New Zealand sites reveal MIS 11 as a prolonged [up to 40 kyr] interglacial period, following a rapid and pronounced 10°C warming from the MIS 12 glacial. Deglaciation occurred 13 kyr earlier than the global benthic record. This rise was punctuated by an Antarctic Cold Reversal-like cooling confirming episodic sub-polar influences at the site. Some differences between the orbital configurations of MIS 1 and 11, particularly at the precessional scale, coupled with apparently unusual ocean chemistry [e.g., low CO₃⁻²] during MIS 11, suggest that MIS 11 may not be an ideal analogue for the Holocene.</p>

Pengaruh Musim Terhadap Distribusi Temperatur, Salinitas Dan Densitas Di Laut Halmahera

<p>Laut Halmahera merupakan salah satu perairan yang memiliki peranan penting bagi perkembangan iklim Indonesia. Wilayah perairan Laut Halmahera merupakan jalur ARLINDO yang menjadi bagian dari sirkulasi arus global. Penelitian ini bertujuan untuk mengkaji profil suhu, salinitas densitas dan diagram T-S di Laut Halmahera secara horizontal dan vertikal. Hasil penelitian menunjukkan bahwa profil horizontal dan vertikal di kedua musim tidak memberikan pengaruh yang signifikan, hal tersebut dapat disebabkan oleh pergerakan massa air <em>New Guinea</em> yang menyusur sepanjang pantai Papua Utara, kemudian masuk ke Laut Halmahera. Diagram T-Smenunjukkan arus yang bergerak di Laut Halmahera secara vertikal termasuk kategori SPSW atau <em>South Pacific Subtropical Water</em>, dibuktikan dengan nilai salinitas 34.7 PSU dan nilai suhu 14^oC pada kedalaman 500 m.</p>

Widespread ice sheet retreat in southern Greenland associated with northward expansion and warming of North Atlantic subtropical water masses

&lt;p&gt;In the past decades a northward expansion of North Atlantic subtropical water masses&lt;sup&gt;1-3&lt;/sup&gt; and warming of subtropical mode water&lt;sup&gt;4,5&lt;/sup&gt; (350 &amp;#8211; 400 m depth) has been observed. Paleoceanographic records from interglacials prior to 400 ka (&amp;#8216;early Brunhes &amp;#8216;) reveal a marked inter-hemispheric climate asymmetry with &amp;#160;the average position of the ocean subtropical front in the eastern North Atlantic having shifted at least 4&lt;sup&gt;o&lt;/sup&gt; latitude to the north&lt;sup&gt;6,7&lt;/sup&gt;. Northward displacement of climate and vegetation belts and previously inferred reduction in sea ice cover at northern high latitudes&lt;sup&gt;7&lt;/sup&gt; has later been confirmed by modelling studies&lt;sup&gt;8&lt;/sup&gt;. North Atlantic ocean circulation was characterized by an enhanced eastern boundary current poleward transport of warm, (sub)tropical&amp;#160; water masses both at surface and subsurface depth&lt;sup&gt;9,10&lt;/sup&gt;. &amp;#160;In recent years (paleo)oceanographic studies of Greenland fjords&lt;sup&gt;&amp;#160; &lt;/sup&gt;have demonstrated&amp;#160; that &amp;#8216;warm&amp;#8217; and saline subsurface water masses of subtropical origin are responsible for sub-glacial melting processes &amp;#160;of Greenland &amp;#160;tide- water glaciers&lt;sup&gt;11-13&lt;/sup&gt;. In periods of the early Brunhes interglacials (MIS 11, 13, 15) during which the eastern North Atlantic was characterized by enhanced northward transport of warm, (sub)tropical water masses&lt;sup&gt;9,10&lt;/sup&gt;, large parts of the southern Greenland Ice Sheet had melted away and a boreal forest could develop here&lt;sup&gt;14,15&lt;/sup&gt; . We conclude that at that time the presence of much warmer, subtropical water masses at subsurface depth in Greenland fjords combined with advection of warm, subtropical air masses with increased precipitation potential from the expanded ocean subtropical gyre region had been responsible for widespread melting of the southern Greenland Ice Sheet. Presently, ongoing &amp;#160;northward expansion and warming of North Atlantic subtropical water masses must therefore be considered to be a process leading to further acceleration of widespread melting of the &amp;#160;(southern) Greenland Ice Sheet.&amp;#160;&amp;#160; &amp;#160;&lt;/p&gt;&lt;ul&gt;&lt;li&gt;1)&amp;#160; &amp;#160;Polovina, J.J. et al. 2008. Geophys. Res. Lett. 35 (3), doi:10.1029/2007GL031745&lt;/li&gt; &lt;li&gt;2)&amp;#160; &amp;#160;Frundt, B. et al. 2013. Progr. Oceanogr. 116, 246-260, doi:10.1016/j.pocean.2013.07.004&lt;/li&gt; &lt;li&gt;3)&amp;#160; &amp;#160;Yang, H. et al. 2020. Geophys. Res. Lett. 47 (5), doi:10.1029/2019GL085868&lt;/li&gt; &lt;li&gt;4)&amp;#160; &amp;#160;Sugimoto, S. et al. 2017. Nature Clim. Change 7, 656-658, doi:10.1038/nclimate3371&lt;/li&gt; &lt;li&gt;5)&amp;#160; &amp;#160;Wu, L. et al. 2012. Nature Change 2, 161-166, doi:10.1038/nclimate1353&lt;/li&gt; &lt;li&gt;6)&amp;#160; &amp;#160;Jansen, J.H.F. 1986. Science 232, 619-622&lt;/li&gt; &lt;li&gt;7)&amp;#160; &amp;#160;Kuijpers, A. Palaeogeogr., Palaeoclimat., Palaeoecol. 76, 67-83&lt;/li&gt; &lt;li&gt;8)&amp;#160; &amp;#160;Kleinen, T. et al. 2014. Quat. Intern. 348, 247-265, doi:10.1016/j.quaint.2013.12.028&lt;/li&gt; &lt;li&gt;9)&amp;#160; &amp;#160;Volker, A.H.L. et al. 2010. Clim. Past, 6, 531&amp;#8211;552,doi:10.5194/cp-6-531-2010&lt;/li&gt; &lt;li&gt;10) Maiorano, P. et al. 2015. Glob. Change 133, 35-48. doi:10.1016/j.glopacha.2015.07.009&lt;/li&gt; &lt;li&gt;11) Straneo, F., Heimbach, P. 2013. Nature 504, 36-43&lt;/li&gt; &lt;li&gt;12) Adresen, C.S. et al. 2011. The Holocene 21(2), 211-224, doi:10.1177/0959683610378877&lt;/li&gt; &lt;li&gt;13) Andresen, C.S. et al. 2013. Shelf. Res. 71, 45-51, doi:10.1016/j.cst.2013.10.003&lt;/li&gt; &lt;li&gt;14) Willerslev, E. et al., 2007. Science 317 (5834), 111-114&lt;/li&gt; &lt;li&gt;15) De Vernal, A. and Hillaire-Marcel, C., 2008. Science 320, 1622-1625&lt;/li&gt; &lt;/ul&gt;

Hyperiid amphipods distribution between the central coast and oceanic islands off Chile, southeastern Pacific

The composition, distribution, and abundance of hyperiid amphipods collected in the oceanographic cruise between the central coast and oceanic islands of Chile in the southeastern Pacific were analyzed. Thirty-four genera and 54 species were identified, grouped into two infraorders and 16 families. The presence of Hemityphis tenuimanus Claus 1879, and Laxohyperia vespuliformis Vinogradov & Volkov 1982, expands its geographical distribution as new records for the southeastern Pacific. According to the founded species, spatial distribution, and the bodies of water present in the study area, Chile’s central region would be a transition zone for species originating from the Magellan Province (Subantarctic water) and the Peru-Chile Province (Subtropical water).

Kirchenpaueria halecioides: a non-native hydroid in the coast of Buenos Aires, Argentina

Hydroid colonies are among the groups frequently carried and introduced by human actions. Many species have been successfully transported as fouling organisms on ship hulls or in ballast water (pelagic stages) and the sea harbours appear as the places with high probability to detect exotic species. During routinely SCUBA diving conducted in Mar del Plata Harbour, Argentina (38°08´S – 57°31´W; May 2005, December 2006, March 2007, and December 2016) clumps of a plumularid were photographed and collected. Hydroid colonies were identified as Kirchenpaueria halecioides, a species frequently reported in tropical and subtropical water from the southwestern Atlantic, Brazil. Records of mature colonies in 2006 and 2016 suggest local reproduction of this non-native species. Monitoring will be necessary in order to analyse if species colonize neighbouring areas or remain confined to the port area.

Karakteristik Massa Air di Perairan Barat Daya Pulau Sumba, Provinsi Nusa Tenggara Timur

Karakteristik massa air dan percampurannya dapat dipengaruhi oleh angin dan aliran air laut ke lokasi tersebut. Massa air laut terbentuk dari komposisi suhu, salinitas, dan densitas pada kedalaman tertentu. Kajian massa air pada perairan barat daya P. Sumba dilakukan menggunakan data hasil reanalysis (karakteristik massa air) seluruh lautan dunia (World Ocean Atlas 2013). Pengolahan data dilakukan berupa sebaran menegak dan melintang suhu dan salinitas, serta menentukan karakteristik massa air. Kisaran suhu perairan P. Sumba musim timur tergolong rendah, SPL berkisar 26.4 - 26.49 oC dan secara umum dari permukaan hingga dasar dengan rentang suhu 26.49 - 3.4 oC. Lapisan termoklin terjadi pada kedalaman 59.67 - 259.38 m dengan kisaran suhu 25.13 - 12.2 oC. Kisaran salinitas permukaan laut dari pantai menuju laut lepas sebesar 34.0498 - 34.1117 psu, dan nilai salinitas secara menegak adalah 34.0498 - 34.7 psu, salinitas maksimum terjadi pada perairan laut lepas, terjadi pada kedalaman dekat termoklin. Pergerakan massa air permukaan pada musim timur diperkirakan akibat angin muson tenggara. Karakteristik massa air yang terdapat ada perairan P. Sumba diperkirakan adalah North Pacific Subtropical Water yang terjadi dekat lapisan termoklin, dengan salinitas 34.55 - 34.7 psu, suhu 12 - 15°C, dan densitas 25.5 - 26. Pada lapisan dalam juga diduga terdapat massa air Indonesian Intermediate Water (IIW), dengan salinitas 34.6 - 34.7 psu, suhu 3 - 7 oC, dan densitas 27 - 27.7.