Alfred Wegener Institute for Polar and Marine Research
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Long-Term Effects of Nutrient Shifts and Warming on Chlorophyll-a in a Temperate Coastal Environment
Get PDFAbstract
Anthropogenically driven nutrient shifts and warming are key stressors affecting phytoplankton in marine coastal environments. The German Bight, a coastal region in the North Sea, has undergone substantial nutrient reductions and rising sea surface temperature (SST) over recent decades. Despite extensive research, the combined long-term effects of nutrient shifts and warming, particularly in the river-influenced coastal area, remain unclear. Here, we aimed to evaluate trends and explore the partial and interactive effects of winter nutrient alterations and seasonal warming on spring chlorophyll-
a
(Chl-
a
) levels. For this purpose, we compiled a comprehensive spatiotemporal dataset (1980–2019) and applied generalized linear mixed models. Results showed that spring Chl-
a
concentrations peaked in the 1980s and 1990s, with values surpassing 30 µg L
−1
in the Elbe estuary. Concentrations declined to < 15 µg L
−1
in the following decades, although values > 15 µg L
−1
persisted in the southern inner coastal waters. Decreasing winter dissolved inorganic nitrogen (DIN) emerged as the primary driver of declining spring Chl-
a
in coastal waters (estimate = 0.40,
p
< 0.01), while winter phosphorus and nitrogen-to-phosphorus ratios were not significant predictors. Spring SST had a weak positive effect on Chl-
a
(estimate = 0.09,
p
= 0.03), suggesting that warming during spring may enhance phytoplankton growth. Together, winter DIN and spring SST explained 30% of the variance in spring Chl-
a
. Additional factors, such as light availability and grazing, likely contribute to unexplained variability. This study provides evidence that nutrient reductions have successfully lowered chlorophyll levels, but persistent hotspots in the inner coastal waters highlight the need for targeted management under continued warming.
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Noisy waters affect feeding and metabolic enzyme activities of amphipod mesograzers
Get PDFThe consequences of the progressive intrusion of anthropogenic noise into natural oceanic soundscapes are largely unknown despite the fact that most metazoans utilize sound or vibration for intra- and interspecific interactions as well as orientation. Coastal ecosystems in particular can be characterized by a high level of human activity and thus anthropogenic noise sources. Here, we studied the impact of such noise on marine mesograzers, small invertebrates that play crucial ecological roles by controlling macrophyte growth while serving as key food sources for higher trophic levels in algae-dominated coastal ecosystems. The effect of added continuous low-frequency noise on the habitat choice, feeding rate, and metabolic enzyme activities of the amphipod mesograzer Marinogammarus marinus was tested in a controlled laboratory setting. While habitat choice appeared unaffected by the added noise, exposed animals exhibited reduced feeding performance as well as altered metabolic enzyme activities. If sustained, the physiological homeostasis of M. marinus and their role in the ecosystem may be jeopardized. The ever-rising sound levels in the oceans may thus have consequences for algae-dominated animal communities in coastal areas
Close Correlation Between Vertically Integrated Tropospheric Water Vapor and the Downward, Broadband Thermal‐Infrared Irradiance at the Ground: Observations in the Central Arctic During MOSAiC
Get PDFThe impact of the vertical distribution of tropospheric water vapor on the cloud‐free downward,
broadband thermal‐infrared irradiance (FTIR) was quantified using observations in the Central Arctic, north of
85°N, collected during the Arctic winter. The water vapor profiles were measured with a temporal resolution of
30 s using a Raman lidar. The observations revealed maximum values of integrated water vapor (IWV) contents
of 3.6 kg m^-2. Seven measurement cases of several‐hour durations of slowly changing air masses were
examined. Furthermore, 53 rather short‐term (10 min) measurement cases were studied. The temporal evolution
of the slowly changing air masses revealed a linear relationship between FTIR and IWV with slopes between 7.17 and 12.95 W kg^-1 and a coefficient of determination larger than 0.95 for most of the selected cases. The slopes
and the ordinate intercepts showed a dependence on the water vapor‐weighted mean temperature (representative
temperature of the water vapor distribution). The temperature determined with the Stefan‐Boltzmann law from FTIR correlated with the representative temperature with a coefficient of determination of 0.92. The analysis of
53 independent short‐term observations of different air masses confirmed the linear relationship between FTIR
and IWV at wintertime cloud‐free conditions in the Arctic (coefficient of determination of 0.75, slope of
19.95 W kg^-1 , and ordinate intercept of 107.22 W m^-2)
Integrating climate change, biological invasions, and infectious wildlife diseases
Get PDFClimate change is likely to affect infectious diseases that are facilitated by biological invasions, with repercussions for wildlife conservation and zoonotic risks. Current invasion management and policy are underprepared for the future risks associated with such invasion‐related wildlife diseases. By considering evidence from bioclimatology, invasion biology, and disease research, we illustrate how climate change is anticipated to affect disease agents (parasites and pathogens), hosts, and vectors across the different stages of invasions. We highlight the opportunity to integrate these disciplines to identify the effects of climate change on invasion‐related wildlife diseases. In addition, shifting to a proactive stance in implementing management and policy, such as by incorporating climate‐change effects either into preventative and mitigation measures for biosecurity or with rapid response protocols to limit disease spread and impacts, could help to combat future ecological, economic, and human health risks stemming from invasion‐related wildlife diseases.</jats:p
Evolution of the Antarctic Ice Sheet from green- to icehouse conditions: Using unique data for advancing numerical model simulations
Get PDFMost ice sheet models indicate that the Antarctic Ice Sheet (AIS) will lose considerable amounts of ice over the coming decades and centuries. This mass loss will mainly be caused by warm deep waters increasingly reaching the AIS’ margins and, with many upstream parts of ice-sheet sectors being grounded far below modern sea level, this will lead to accelerating and irreversible retreat. Are we therefore currently witnessing the initiation of runaway retreat of large parts of the ice sheet that will result in rapid sea level rise resulting in severe consequences for global coastal communities? Finding more reliable answers to this question requires robust multi-proxy data evidence from AIS-proximal records spanning times that were warmer and CO2-richer than today. Such sediment records are rare and challenging to obtain, requiring drilling campaigns that are only feasible within large multinational consortiums. Some extensive Antarctic field campaigns, however, were recently realized, are about to be accomplished, or at the planning stage. This presentation will introduce these campaigns and highlight how their results combined with novel coupled modeling techniques will eventually provide significant new insights into the AIS’ long-term evolution. This information will allow for better predictions of its response to conditions anticipated for the foreseeable future
The Role of Ballasting, Seawater Viscosity and Oxygen‐Dependent Remineralization for Export and Transfer Efficiencies in the Global Ocean
Get PDFAbstractThe particulate organic carbon (POC) flux from the euphotic zone to the deep ocean is central to the biological carbon pump. It is typically evaluated using “export efficiency” and “transfer efficiency,” which reflect POC formation and sinking and carbon sequestration efficiency in the ocean's interior, respectively. Since observations of these metrics are limited, biogeochemical models can elucidate the controls of large‐scale patterns. This study uses the global ocean‐biogeochemical model FESOM‐REcoM, with a new sinking routine that accounts for ballast minerals, seawater viscosity, and oxygen‐dependent remineralization in POC sinking and remineralization, to identify the drivers of global export and transfer efficiency. We find that export efficiency is highest at high latitudes, where diatoms, mesozooplankton, and macrozooplankton dominate the plankton community, but that high export efficiency does not always imply high transfer efficiency. Omitting ballast minerals decreases export efficiency by 20% in the Southern Ocean, yet the globally integrated POC flux out of the euphotic zone (5.4–5.6 Pg C ) and the global average export efficiency (14.7%–15.4%) are relatively insensitive to seawater viscosity, mineral ballasting, or oxygen‐dependent remineralization. In contrast, global transfer efficiency is more sensitive to these processes and varies between 21% and 25% in the simulations, with the largest reduction by 23% observed when omitting ballasting in subtropical, low‐productivity regions. Our findings suggest that assumptions about ballasting and background sinking speed could explain previous discrepancies in the literature regarding the highest transfer efficiencies in low or high latitudes. Notably, while plankton community structure determines export efficiency regimes, zooplankton fecal pellets drive high transfer efficiencies in regions with high export efficiency, like the Southern Ocean.</jats:p
Exploring the land-use futures related to reindeer herding in Finland through “wild logic” scenarios
Get PDFDrifting Snow around Icebergs: Understanding the Role of Iceberg Size and Shape Through Modeling and Observational Data
Get PDFThe genesis of snowdrifts and its governing processes are not fully understood. In Antarctica, understanding snow movement is crucial for assessing ice sheet mass balance and tackling logistical challenges related to human infrastructure. So far, extensive research has focused on snow‐wind interactions on flat terrain, emphasizing the crucial roles of flow turbulence and snow properties. This work expands an existing Eulerian‐ Lagrangian model by incorporating buildings to simulate snowdrifts around complex structures, using advanced saltation physics. The German Antarctic research station Neumayer III is used as a test site. This development brings new levels of interaction between snow particles and larger structures, making the simulations more representative of real‐world conditions. Specifically, numerical simulations were conducted to test the influence of six parameters on snowdrift formation, namely: wind force, snowbed cohesion, particle diameter, precipitation rate and building height and shape. Results show that the size of snowdrifts is mostly affected by wind force, preferential deposition and snowbed cohesion, while fine features of the building shape control their form. Nevertheless, significant uncertainties remain regarding the interaction of these parameters, highlighting the need for further research to improve modeling frameworks. This study demonstrates that our model is well suited for engineering applications, guiding optimal designs for buildings and infrastructure in snow‐affected environments
Assessment of the southern polar and subpolar warming in the PMIP4 last interglacial simulations using paleoclimate data syntheses
Get PDFGiven relatively abundant paleo-proxies, the study
of the last interglacial (LIG,∼129–116 000 years ago, ka)
is valuable to understanding the responses and feedback
of the Southern Ocean and Antarctica in a warmer-than-
preindustrial climate. The Paleoclimate Modelling Intercomparison Project Phase 4 (PMIP4) coordinated LIG model simulations which focus on 127 ka. Here we evaluate 12 PMIP4 127 ka Tier 1 model simulations against four recent paleoclimate syntheses of LIG sea and air temperatures and sea ice concentrations. The four syntheses include 99 reconstructions, and all syntheses support the presence of a warmer Southern Ocean, with reduced sea ice and a warmer Antarctica at 127 ka compared to the preindustrial. The PMIP4 127 ka Tier 1 simulations, forced solely by orbital parameters and greenhouse gas concentrations, do not capture the magnitude of this warming. Here we follow up on previous work that suggests the importance of preceding deglaciation meltwater release into the North Atlantic for the early last interglacial climate. We run a 3000-year 128 ka simulation using HadCM3 with a 0.25 Sv North Atlantic freshwater hosing, which approximates the PMIP4 127 ka Tier 2 H11 (Heinrich event 11) simulation. The hosed 128 ka HadCM3 simulation captures much of the warming and sea ice loss shown in the four data syntheses at 127 ka relative to preindustrial: south of 40° S, modeled annual sea surface temperature (SST) rises by 1.3 ±0.6 °C, while reconstructed average anomalies range from 2.2 to 2.7 °C; modeled summer SST increases by 1.1 ±0.7 °C, close to the 1.2–2.2 °C reconstructed average anomalies; September sea ice area (SIA) is reduced by 40 %, similar to the reconstructed 40 % reduction of sea ice concentration (SIC); over the Antarctic Ice Sheet, modeled annual surface air temperature (SAT) increases by 2.6 ±0.4 °C, even larger than reconstructed average anomalies of 2.2 °C. Our results suggest that the impacts of meltwater from deglaciating ice sheets need to be considered to simulate the Southern Ocean and Antarctic changes at 127 ka
Newly dated permafrost deposits and their paleoecological inventory reveal an Eemian much warmer than today in Arctic Siberia
Get PDF-In this study, we integrate geochronological, cryolithological, paleoecological, and modeling data to reconstruct the Last Interglacial (LIG) climate around the New Siberian Islands, revealing significantly warmer conditions compared to today. New luminescence dating of the lacustrine deposits mostly preserved in ice-wedge pseudomorphs of 1–3 m thickness along the Dmitry Laptev Strait indicates ages consistent with the LIG (Marine Isotope Stage (MIS) 5e). Analysis of plant macrofossils and of pollen and faunal records (beetles and chironomids) from these deposits suggests mean temperatures of the warmest month (MTWAs) of 10.3 to 12.9 °C, 9.0 ± 3.0 °C, 8 to 10.5 °C, and 9.4 to 15.3 °C for Bol'shoy Lyakhovsky and of 12.7 to 15.3 °C, 9.7 ± 2.9 °C, 8 to 14 °C, and 12.0–13.8 °C for Oyogos Yar. The fossil-beetle-based mutual climate range for mean temperatures of the coldest month is −34 to −26 °C for Bol'shoy Lyakhovsky and −38 to −26 °C for Oyogos Yar. Our chironomid-based reconstructions of water table depth suggest 1.7 to 5.6 m for Bol'shoy Lyakhovsky, while previous analysis suggested 1.1 to 3.3 m for Oyogos Yar. Pollen-based reconstruction of mean annual precipitation (MAP) suggests 271 ± 56 mm for Bol'shoy Lyakhovsky and 229 ± 22 mm for Oyogos Yar. The first-time application of clumped isotopes to permafrost-preserved biogenic calcite of ostracods and bivalves for Oyogos Yar reconstructed near-surface water temperatures of 10.3 ± 3.0 °C and bottom-water temperatures of 5.3 ± 1.5 °C in thermokarst lakes during summer. In summary, the analyzed proxies suggest summers warmer than today by 5.5 to 12.8 °C for Bol'shoy Lyakhovsky and by 0.2 to 7.5 °C for Oyogos Yar and winters warmer than today by up to 7.1 and 8.4 °C for Bol'shoy Lyakhovsky and Oyogos Yar, respectively. Modern mean annual precipitation values are within the uncertainty range of the reconstructions. Climate model simulations for the LIG from PMIP suggest MTWAs warmer than today for Bol'shoy Lyakhovsky (4.4 ± 1.0 °C compared to 2.5 °C) and colder than today for Oyogos Yar (4.5 ± 1.2 °C compared to 7.8 °C), underestimating the Eemian warming reconstructed from our multiple paleoecological proxies. The LIG warming mainly affected summer conditions, whereas modern and future warming will rather impact winter conditions. As the LIG annual mean temperature is often used as an analog for the future climate in the High Arctic, the proxy–model mismatch highlights the urgent need for more systematic quantitative proxy-based temperature reconstructions in the Arctic and more sophisticated Earth system models capable of capturing Arctic paleoenvironmental conditions