Ice, water and sediments: a cold, wet and muddy account of a very fun life in science
A cold and wet start
These activities were always fascinating for me and are still a kind of “hobby,” and even resulted in a short story (Björck 1991) in the Swedish literary magazine Ord och Bild. The theme of the story was based on fieldwork on Jameson Land in east Greenland in 1990. During the weeks in the field, we experienced nine full days of rain, which amounted to a whole year of normal precipitation in this fairly arid region. Our camp, consisting of Olafur Ingolfsson’s, Mats Rundgren’s and my own tent, plus a kitchen tent (Fig. 3), became completely flooded by water; permafrost prevented the water from infiltrating downward. I felt like I was in heaven! I started to canalize the standing water in the camp down to nearby Lake Boksehandsken (Boxing Glove!) in an intricate way, and with help from Olafur and Mats this resulted in a complex system of canals, which the helicopter pilots called “The Venice of Greenland.” As long as the rain continued, our drainage system had to be maintained, and even my colleagues were caught up in this activity that prevented the tents from being totally flooded. This special experience resulted in the short story Vattentagen (in English, “Watertaken”). My 14-years-old daughter Åsa was very impressed that her father had published a real story and was convinced that we would now become rich! According to her, real authors, not researchers, earn loads of money!!
When looking back at my career, the element of water has remained central, both during my education and in my research. After finishing high school in Malmö and studies in Mathematics and Geology at Lund University (LU), I spent a compulsory year in the Navy (once again water!). I moved to Gothenburg in the early 1970s for studies in Oceanography, mainly Physical Oceanography, which was a subject I greatly enjoyed. For a while I intended to become an oceanographer, and after 1 year of studies I planned for a Master’s thesis. When I was then informed that one needs to own a boat or at least rent one to conduct field work for the Master’s thesis, I became very disappointed, since this was beyond my student budget. I therefore decided to return to LU and study Limnology. By chance, I saw a recently published PhD thesis in Quaternary Geology, which dealt with the area around our family house in the province of Halland, between Göteborg and Lund. I had often stayed there a month or so during summers with cousins and second cousins, and had enjoyed the clear water of nearby spring-fed Lake Skärsjön, sailing and swimming. With excitement I read about the glacial landforms surrounding the lake and now redirected my plans towards Quaternary Geology.
After my Master’s thesis in Quaternary Geology (1972), which focused on an ice margin delta in Halland, I worked with mapping for the Swedish Geological Survey (SGU) in Skåne, as well as hydrological work in South Halland, and I was offered an opportunity to undertake a PhD. But doing what? My own idea was to work on a topic related to groundwater and geology, i.e. hydrogeology. As a young boy, I spent 3 years in India and Iran, and the memory of women carrying water buckets on their heads to their villages had never left me. Poor people need wells in their villages to live decent lives. Water is the most critical resource we have and I could perhaps make a difference? But once again, chance came into play. Björn Berglund and Erik Lagerlund had come up with a fascinating PhD topic: spatial and temporal relationships between raised deltas in the province of Blekinge and the shore displacement of the Baltic Ice Lake (BIL), the glacial lake that occupied the Baltic Basin until the onset of the Holocene. Would I be interested in such a project? As a “water person” this was very tempting; the impact of water from glacial rivers on the beautiful landscape of Blekinge, SE Sweden, and the lake level variations of the large BIL and its impact on the Blekinge shores, sounded extremely fascinating. Moreover, Blekinge is the province where I was born 25 years earlier! I could not resist their offer, especially in light of their enthusiasm for the topic.
I began my PhD studies in the mid-1970s by documenting the sedimentology and stratigraphy of numerous gravel pits in several of the river valleys of Blekinge. The other part of the field work was to reconstruct the shore displacement following deglaciation. To accomplish that, I needed to drill the oldest sediments in lakes situated at different altitudes below the highest shoreline, i.e. the shoreline that formed during or right after deglaciation, and estimate the age when the water bodies had become isolated from the BIL. Most of this work was carried out in winter from lake ice with Russian peat samplers or Livingstone piston corers, and in a few instances, we even cored from unstable, thin ice flakes. Although this was almost as exciting as the experiences of my youth, I found something even more exciting: the beauty and fascinating stratigraphy of late glacial lake sediments. Much of what I first saw, in terms of lithologic variability, was puzzling, and I was bewildered! Every lake had its own sedimentological character, and one never knew what to expect when daylight exposed the content of the corer; a new world of experiences opened up! Ever since those first drillings, I have been thrilled by the first sight of sediment cores from a new lake.
My studies in gravel pits were mostly carried out in the beautiful summer landscape of Blekinge, often termed “the garden of Sweden,” in stark contrast to the ice-cold lake drillings in winter. Since most of the raised deltas, and therefore also the gravel pits, are situated in river valleys, I was always close to running water and to river systems that once drained the retreating ice sheet. The deltas often contained rich information on the general lithostratigraphy of Blekinge, usually with stunning glacial varved clay (Fig. 6) as their lowest unit, a unit that was also often found in the bottom of the lake cores. With the aid of pollen analysis and 14C-dated lake sequences from different altitudes up to 70 m a.s.l., I planned to determine the age of the top-set beds in the different raised deltas of the BIL. Nevertheless, because the lakes that are today situated below the highest shoreline (67 m) were once bays in the glacial and barren BIL, and as a consequence of glacial unloading ended up as freshwater lakes, it was challenging to find “isolation indicators” other than diatoms. I finally, however, ended up with nine more-or-less good indicators, such as magnetic susceptibility, Pediastrum, loss-on-ignition, reworked pollen/spores.
I truly enjoyed life as a PhD student, both professionally and socially. I attended many good PhD courses, most of them at other Nordic universities, and became part of a network of Nordic PhD students. It was great to focus on a really fascinating topic, deepen my knowledge, and try to come up with new, though often half-baked ideas. Together with the lake drilling, the writing phase of my PhD work was the part that I most enjoyed. In my personal life, my greatest enjoyment was the birth of my lovely daughter Åsa in November 1977, for whom 12 years later, I named one of the lakes I cored in Antarctica. My thesis, which I defended in May 1979, was published as a monograph on the Quaternary lithostratigraphy and late glacial pollen stratigraphy of Blekinge. It included a shore displacement curve for the BIL and the hypothesis of a catastrophic drainage of the BIL at the Younger Dryas–Preboreal boundary. This drainage, which was on the order of 25 m, had regional implications for the Baltic Sea Basin. The PhD thesis was later published in Fossils and Strata (Björck 1981).
During the last years of my PhD education, Björn Berglund and Gunnar Digerfeldt invited several foreign visitors, guests and post-docs to the department. They included, among others, Peter Beales, John Birks, Rick Battarbee and John Dearing, and many close friendships were formed. John Birks led a PhD course in multivariate statistics and I was flabbergasted. Peter Beales became a close friend and checked the English text of my thesis, and together with John Dearing, I published my 6th paper (Björck et al. 1982). One thing that astonished me was how young the English post-docs were! In Sweden it was very rare to be younger than 30 years old at the time of one’s PhD defense. Immediately after I defended my PhD (Matti Saarnisto was a very friendly opponent), I worked for half a year for the province of Blekinge, documenting geologically interesting sites.
1980s: wider perspectives
In the early 1980s I had a temporary, part-time position at the department with some teaching, but mostly research. Together with Gunnar Digerfeldt, who is my true paleolimnological role model, we decided to create late glacial sea level curves for southwestern Sweden. In contrast to Blekinge, this was a region that had experienced a glaciomarine deglaciation, and it was therefore easier to determine the isolation horizons with diatom analyses. Through comparisons between the Baltic Ice Lake development and the sea level development along the Swedish West Coast, we were able to better understand the dynamics of the late glacial development of the up-dammed Baltic Basin. During this very intense field work period, we cored many lakes, mainly from ice, and analyzed the sediments using geochemical variables, pollen and diatoms. The latter work was carried out by Hannelore Håkansson, an amazing diatom taxonomist. Over the years this resulted in six Björck and Digerfeldt papers. The field work ventures with Gunnar are still very special memories: walking through deep snow with our sled, drilling through meter-thick ice, coring to the bottom of the lake sediments, discovering and describing new, unseen sediment sequences, drinking strong hot coffee and smoking our pipes, and ending up trying to convince hotel personnel that the cores had to stay indoors to prevent them from freezing. And I learned a lot from Gunnar about drilling techniques and how to describe sediments, but perhaps most of all, about coming up with and testing “half-crazy” ideas based on what we saw in the cores; it was certainly the perfect “lake-sediment-school”!
In June 1979 Herb Wright Jr. came to visit Björn and was given my thesis as evening literature! “What a bore,” I thought, but a few days later Herb approached me and asked if I would be interested in joining his group in Minnesota, as a post-doc. He (and Björn) had the idea that I should apply to the Swedish Natural Science Research Council (NFR) for a guest researcher scholarship, a newly started NFR program. Since I both liked and was impressed by Herb, and I had never visited the U.S., I accepted the idea, wrote an application and was granted a 1-year scholarship in late 1980.
Most of my time at the LRC was devoted to analysis of the sediment lithology of the four selected lakes and their pollen and plant macrofossil assemblages. I spent the first few months learning many new pollen types, but after a while, counting became much easier because coniferous pollen grains were abundant and dominant. Most of the pollen work was carried out at the LRC, but some of the work also continued in Lund, after we moved back in May 1982. The study, which was published in 1985 (Björck 1985), inferred a long phase of park-tundra in the south, in contrast to a very short tundra period during the Holocene deglaciation farther north. It also highlighted the complex spread of white pine and alder and the peak influx of prairie pollen during the mid-Holocene spread of white pine. The distinct change in sediment composition and the disappearance of ash and elm pollen during the Younger Dryas caused much discussion; a Younger Dryas cooling in the U.S. was hardly accepted at that time, and I heard colleagues saying “it’s only Europeans who find a Younger Dryas here.” I was therefore not allowed to mention “Younger Dryas” in the published article, but “suggested cool period” was fine. A few years later it became more accepted that this cooling impacted at least parts of North America, especially along the east coast, but also further inland in the U.S., e.g. in Ohio as was shown by Linda Shane (Shane 1987) from the LRC.
Back home I focused on my sea level collaboration with Gunnar and also on chronological issues related to deglaciation dynamics (Björck and Möller 1987), Baltic Sea development and paleomagnetism (Björck et al. 1987) with Per Möller, Per Sandgren and Benneth Dennegård and some very talented PhD students such as Bodil Liedberg-Jönsson, Geoffrey Lemdahl and N-O Svensson. Much of our work focused on drilling unexplored lakes that contained the most beautiful sediments, but also less beautiful Baltic Sea sediments. It struck me, over and over again, how individual each lake is in terms of its sediments and stratigraphy. Some of the Swedish lake sediments were more similar to some of the North American sediments than to sediments in a neighboring lake. Each lake seemed to have its own history, just like a living organism, at least when it came to lithologic details. Although I had by then seen many lake sediment cores, it was still impossible to foresee what would emerge from the bottom of each new lake; the thrill of probably being the first person to ever see a sediment core from a lake, has followed me throughout my career.
1990s: new colleagues, new scientific problems, new areas, new cores, new adventures
For many years, I had been fascinated by the complex Baltic Sea history. The final drainage of 25 m from the large Baltic Ice Lake was eventually accepted when Bo Strömberg in 1991 found open pits with impressive boulder-pebble deposits, 7 km from Mt. Billingen. I was, however, frustrated by the fact that several eminent geologists had often focused their interest on only one, or in some cases two, of the 4–5 Baltic Sea stages, but without clarifying the puzzling transitions to tie the whole story together. A special problem was the enigmatic Ancylus Lake stage, a key stage in the early Holocene, about which many different opinions existed. Given my interest in and research on sea level on the Swedish West coast and the Baltic Sea Basin, I was at a point where I felt prepared to explain some of the “mysteries” connected to the transitional phases. In 1993 I was invited by Thomas Andrén to present a keynote address at a Baltic Sea meeting on my thoughts about the Baltic Sea history. To my surprise, the response was very positive, at least from most of the attendants. The next task was to publish it, with maps and convincing facts. By creating a large number of shore-line diagrams, I estimated water levels around the Baltic coast for different time slices, with Barbara drawing the maps that would become so important (Björck 1995). This publication is one of the few of which I am proud because the main findings are still accepted, although some details have changed and new findings have been published over the years, e.g. a calendar-year-based chronology of the whole Baltic Sea history (Björck 2008; Andrén et al. 2011). The Baltic IODP 347 proposal, with Thomas Andrén and me as lead authors, resulted in the 2013 expedition that had six drill sites. Study of those cores will, in the near future, lead to many new insights about Baltic Sea history. One recent discovery, unrelated to IODP, comes from our submarine studies of a submerged landscape east of Skåne in southernmost Sweden, in collaboration with archaeologist Björn Nilsson. Numerous pine trees were found on the modern sea floor. By using a combination of 14C dating and dendrochronology to date the death of the pine trees, our recently graduated PhD student Anton Hansson was able to determine the detailed course of the Ancylus Lake transgression. Anton showed that the pine trees had been flooded (and killed) by the Ancylus transgression, and established the timing of the transgression in great detail (Hansson et al. 2017). This was a dream I had harbored for more than 25 years and now it was accomplished, which felt great!
In 1994 I became the first Quaternary Geology professor in Copenhagen, Denmark, which was an honor, especially for a Swede! Denmark had fostered many pioneers in Quaternary geology, such as K. Jessen, J. Troells-Smith, J. Iversen, and S. Th. Andersen, but it had never developed there into a full-fledged geological subject, as it had in Finland, Norway and Sweden, despite the fact that Denmark is totally covered by Quaternary deposits. There were several excellent colleagues in Copenhagen who worked on Quaternary issues, for example Michael Houmark-Nielsen (South Scandinavian glacial stratigraphy), Svend Funder and Ole Bennike (Quaternary of Greenland). Ole and I have cooperated ever since the mid-90s on many amazing projects. In terms of field work, we are both adventurous, which has resulted in many exciting findings, for example mild Younger Dryas summers in Greenland (Björck et al. 2002). For our field work, we used both a helicopter and a Zodiac dinghy to reach our coring sites. Many of the lake sequences we drilled in Greenland were spectacular, especially those with marine-lacustrine transitions in the archipelago of SW Greenland. These latter cores enabled us to present a sea level curve, led to a long-standing cooperation with our great colleague Kurt Lambeck, and generated a model of the SW Greenland ice sheet (Bennike et al. 2002). The years in Denmark also involved much field work, often with Master’s students in different parts of Denmark, the Faroe Islands and Greenland. We were lucky that the few cold winters in Denmark made it possible to drill from lake ice, resulting in some exceptional Late Glacial and Holocene sediment sequences. When the scientific debate on the climate stability of the Last Interglacial (Eem) started in the mid-90s, an Eemian ancient lake sequence on Jutland, previously pollen analyzed by Svend Th. Andersen (Andersen 1965), caught my attention. We sampled the open lake section and together with colleagues at the Geological Institute, e.g. Michael Houmark-Nielsen and Nanna Noe-Nygaard, we analyzed a range of climate proxies. Our study (Björck et al. 2000) showed that this ancient lake had been influenced by fairly large hydroclimate changes, and that the Eemian in southern Scandinavia was perhaps more variable than the Holocene.
Another challenge was to date lake sediments from Lake Igelsjön in the Billingen area, with U/Th. These Holocene sediments are dominated by compact algal and carbonate gyttjas, and were some of Gunnar’s and my favorite lake sediments, in terms of beauty. Parallel U/Th and 14C dating, in collaboration with our postdoctoral researcher Carsten Israelsson and with Chris Hawkesworth, showed that this type of sediment could indeed be dated using U/Th (Israelson et al. 1997). It still surprises me that U/Th dating is not used more often for this specific sediment type. Another highlight from Lake Igelsjön was that Dan Hammarlund, together with me and Danish colleagues, were the first to detect a clear climate response of the 8.2-ka event in a Swedish lake, using stable isotopes (Hammarlund et al. 2003).
Other highlights in the late 1990s were summer schools in Switzerland and Iceland for PhD students and post-docs, where I also met Gerard Bond and Raimund Muscheler. The vivid discussions with Gerard are memorable, and Raimund would, in the early 2000s, become a post-doc in Lund and later an important member of the Lund Quaternary group, ending up in 2015 as my successor as Head of Quaternary Science in Lund.
The enthusiasm of my 15 Danish Master’s students was important for my well-being during the 6 years in Copenhagen. Sigfús Johnsen and his ice core group at the Niels Bohr institute also played a crucial role. Sigfús inspired my research in Copenhagen and during the subsequent years in Lund. I learned much from his open-mindedness in terms of scientific problem-solving, very similar to Gunnar Digerfeldt’s approach. Sadly, he died in 2013, but his creativity, knowledge and generous and warm personality will remain in my memory forever.
In hindsight, the bipolar seesaw mechanism was possibly the most important and fascinating scientific finding for me during my career and would become crucial for my future research. It was formulated and later theoretically depicted by three giants in our field of science: Wally Broecker (Broecker 1998), Sigfús Johnsen and the youngster Thomas Stocker (Stocker and Johnsen 2003). With great celebrations, Wally received the Crafoord Prize from Queen Silvia in Lund in 2006. He died at the age of 87 on 18 February 2019. A true giant has left us.
2000s: new challenges
In the late 1990s two of my most seminal papers were published (Björck et al. 1996, 1998). These were team works, partly inspired by Sigfús Johnsen, Bernd Kromer and the INTIMATE group, to synchronize ice cores, marine sediments and lake and terrestrial deposits. I had also applied for a professorship in Quaternary Geology at Lund University, which had become vacant after my former PhD supervisor Björn Berglund retired. When I was offered the position, I gladly accepted, partly because commuting between Lund and Copenhagen was tiring and time consuming (although, ironically, the Öresund Bridge opened the same day, July 1st 2000, I started in Lund!), and partly because of the strong multidisciplinarity of the Lund Quaternary group, with many PhD students, in contrast to Copenhagen. Björn had been a pioneer in modern paleoecology, but had also contributed tremendously to modern research education, so it was a great challenge to take over and lead.
The Greenland modeling and sea level work continued and was concluded superbly by my PhD student Charlotte Sparrenbom (Sparrenbom et al. 2006). All the PhD students I have supervised from the mid-90s into the early 2010s have succeeded extremely well within the university or the corporate world: Dan Hammarlund, stable isotopes and paleoclimate; Hui Jiang, diatoms and North Sea paleoceanography; Mats Rundgren, Icelandic sea level changes and vegetation history; Camilla S. Andresen, paleoclimate in North Iceland-South Greenland based on marine and lake sediments; Rixt de Jong, Holocene vegetation and wind history in SW Sweden; Karl Ljung, paleoclimate studies on Tristan da Cunha, and Johan Striberger, climate history of Lake Lögurinn, East Iceland. All of them had one thing in common: their often thrilling results were based on beautiful sediment cores that inspired their curiosity. I am also extremely happy to have had the opportunity to continue cooperating with my former graduate students after they graduated. Of my > 160 publications after 1993, one or more of my (usually former) PhD or Master’s students were 1st author or co-author on 75, i.e. > 45%.
The paleoclimatic and paleoenvironmental data sets of the “Atlantis Project” would not have been possible to obtain without the engagement of many of my fantastic colleagues, post-docs, PhD and Master’s students from 17 countries, e.g. Florian Adolphi, Yamoah Afrifa, Camilla S. Andresen, Paul Baker, Lena Barnekow, Ole Bennike, Anders Bjørk, Stein Bondevik, Daniel Conley, Anders Cronholm, Marilen Fernandez, Roger Flower, Sheri Fritz, Marianne Grauert, Charlotte Greve, James Haile, Ladislaw Hamerlik, Dan Hammarlund, Christian Hjort, Sofia Holmgren, Michael Houmark-Nielsen, Olafur Ingolfsson, Catherine Jessen, Hui Jiang, Masa Kageyama, Kurt Kjær, Bernd Kromer, Malin Kylander, Eiliv Larsen, Hanna Lindvall, Karl Ljung, Astrid Lyså, Elisabeth Michel, Raimund Muscheler, Per Möller, Jesper Olsen, Juan Federico Ponce, Charles Porter, Jorge Rabassa, Jayne Rattray, Hans Renssen, Tammy Rittenour, Peter Rosén, Mats Rundgren, Jesper Sjolte, Rienk Smittenberg, Ian Snowball, Thomas Stocker, Johan Striberger, Ingmar Unkel, Cinthia Uvo, Nathalie Van der Putten, Stefan Wastegård and of course Barbara Wohlfarth! Of these more than 50 co-workers, more than 25 joined me on one or more of the island expeditions and field work. The multidisciplinary character of this research also necessitated the involvement of many specialists.
The complex logistics of field work on far-away islands has meant that much time during the 2000s had to be spent on organization, but also on doing the field work and analyzing the spectacular sediments. I have often been asked where my favorite field work area is, but the answer to this question is tricky. Without doubt, the Antarctic settings are the most beautiful, especially if one includes the fascinating fauna—penguins and other sea birds, seals and whales.
We definitely had to go back to Nightingale Island! In January 2010, after a long preparation, we set sails from the Falkland Islands with Charlie Porter’s ketch-rigged sailing boat Ocean Tramp. After 2 weeks of sailing with hard westerlies through the screaming 50s and roaring 40s, and with up to 15-m-high waves, we arrived at Nightingale Island and could begin our 2 weeks of field work. This island must be one of the most fascinating, but also remote, field work areas one can imagine. We stayed in huts made by the Tristan islanders for their annual visit to collect eggs, among colonies of 3 million pairs of great shearwaters, 125,000 pairs of rock-hopper penguins, 10,000 pairs of broad-billed pion and storm petrels, 5000 pairs of yellow-nosed albatrosses, thousands of fur seals, surrounded by a vast and never-ending roaring ocean with its fish and lobsters for evening barbecues. The unique memories from these weeks will never fade! The same goes for the memorable trip back to a “stable” continent. After a few days of sailing against the westerlies and towards the Falklands/Malvinas, it became obvious that such an undertaking was not feasible. We therefore sailed north to catch more favorable winds and after 33 days of sailing in highly variable weather, we ended up in Uruguay with our more than 50 sediment cores. The day we landed in Punta del Este, found a hotel, had our first shower in more than a month, and had a fantastic dinner with great Uruguayan wine, stands out as one of those extraordinary experiences. It is also an example of what I find so fascinating with what we as field-work-dependent scientists have a chance to experience: the large contrasts between often very tough conditions in the field, cold-windy-wet-dirty, and the coziness and comradery in a kitchen tent, around a camp fire or a dinner table, after days or weeks of work. Contrasts like that, experienced with close colleagues, in combination with a good “harvest” of sediment cores, raises my life quality considerably. As geologists and paleolimnologists, we should continuously remind ourselves and our students about the very special opportunities our scientific field provides us.
Fieldwork-related experiences are very different from the administrative duties that we all need to carry out. I served as a member of the Earth Science Panel of the Swedish Research Council (VR) for many years and enjoyed it, mostly because of my general interest in research. When asked to run for (and later elected), I was happy to become a member (and later chair) of the Board for Natural and Technical Sciences at VR between 2007 and 2012. Those years gave me many new perspectives on science. General reflections from that time indicate that the best ways to maintain strong basic research are to strive for high quality among the members of different scientific panels; to convince politicians that basic research is the platform for all research; to prioritize individual, smaller, often more productive research projects; and to elect active university researchers to the boards of the grant funding research councils/foundations, as is done for example at VR, but with a restriction of a maximum service period, to avoid corruption, which may occur with long periods of power.
In the above accounts, I described field work, sediment cores, PhD supervision and science, but another important component for my well-being has been to teach and stimulate undergraduate and graduate students. My teaching load has varied over the years, usually between 20 and 40%, and it was never a burden, not even in Copenhagen where I often had more than 50%. Instead, I have usually felt very good and “productive” after a few hours of teaching students about some of the exciting revelations that the geologic record holds, and making them realize that we usually have only a few pieces in a giant puzzle; the challenge is to add a few more pieces, and gradually create the larger picture, in spite of the fact that most pieces are still lacking. Although I have received nominations and prizes for my research accomplishments, I am most proud of the teaching prize I received from the Science Faculty students in Copenhagen in 1997, in spite of my strong Danish–Swedish accent!
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